Update on 1 benzylpiperazine (BZP) party pills
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Arch Toxicol (2013) 87:929–947
DOI 10.1007/s00204-013-1057-x
REVIEW ARTICLE
Update on 1‑benzylpiperazine (BZP) party pills
Márcia Sá Monteiro · Maria de Lourdes Bastos ·
Paula Guedes de Pinho · Márcia Carvalho
Received: 25 February 2013 / Accepted: 3 April 2013 / Published online: 18 May 2013
© Springer-Verlag Berlin Heidelberg 2013
Abstract N-benzylpiperazine (BZP) has become popular Keywords Benzylpiperazine · Piperazine derivative ·
among recreational drug users as the major active ingredi- Legal highs · Pharmacokinetics · Pharmacodynamics ·
ent of “party pills” due to its stimulant and euphoric prop- Toxicity
erties. Before BZP legal restrictions, these pills were sold
as a safe and legal alternative to classical amphetamines
like ecstasy. New Zealand, given the size of its legal market “Legal highs” and the emergence of piperazine
prior to BZP control, is the country that most contributed derivatives
to the knowledge about the patterns of use, motivations and
positive and adverse effects resulting from its consumption, Drug abuse remains a major global health issue, and over
though the interest in BZP-party pills was observed all over the last years, there has been an emergence on new unreg-
the world. The use of these pills has been associated with ulated psychoactive compounds. These substances are
hospitalizations for adverse events and continued availabil- known and marketed as “legal highs” or “herbal highs”
ity over the Internet makes this intoxication a continued and include a wide variety of natural (herbal), semisyn-
concern. This paper provides a review on the characteristics thetic and synthetic substances which are designed to cir-
of BZP recreational use, specifically the target population, cumvent drug controls and mimic psychoactive effects
patterns and motivations of use, and evolution of legal sta- of illicit drugs. “Legal highs” are available in a variety of
tus. Moreover, the in vivo and in vitro studies performed formulations and are mainly purchased on Internet web-
in order to understand its pharmacology, toxicology and sites or from street retailers (smart shops or head shops)
kinetics are also discussed. Lastly, analytical methodolo- (EMCDDA 2010; Zawilska 2011). These substances have
gies for the identification of BZP in clinical and forensic experienced a rapid increase in popularity mostly attrib-
settings are addressed. uted to their promotion as “legal,” “natural” and “safe,” to
aggressive web-based marketing (Burillo-Putze et al. 2011;
Zawilska 2011) but also to associations with street illegal
drugs (e.g., names and symbols/logos) (EMCDDA 2007a).
The “legal high” market has a singular characteristic
because after a ban of a particular substance, novel com-
M. S. Monteiro (*) · M. L. Bastos · P. Guedes de Pinho · pounds quickly appear (in order to evade the law) and are
M. Carvalho advertised as being better than the previous ones (Winstock
REQUIMTE, Laboratory of Toxicology, Department of
and Ramsey 2010; Zawilska 2011). It should be noted that
Biological Sciences, Faculty of Pharmacy, Porto University,
Rua Jorge Viterbo Ferreira, 228, 4050‑313 Porto, Portugal the vast majority of these novel drugs have not been tested
e-mail: aicram_monteiro@hotmail.com for their safety (lack of pharmacological and toxicologi-
cal information), and as they are not covered by any drug
M. Carvalho (*)
legislation or control, the potential health implications of
Faculty of Health Sciences, Universidade Fernando Pessoa,
Porto, Portugal their use are largely unknown and difficult to predict (Gee
e-mail: mcarv@ufp.edu.pt and Fountain 2007; Staack and Maurer 2005; Zawilska
13930 Arch Toxicol (2013) 87:929–947
2011). The use of these products is normally based only in controls over these drugs, piperazines were sold as legal
users’ opinions (Burillo-Putze et al. 2011; Zawilska 2011) alternatives to amphetamines (generally blends of pipera-
and on the market advertisement, which, usually, does zines), but also in tablets sold as methylenedioxymetham-
not refer the presence of psychoactive compounds on the phetamine (MDMA; ecstasy) or amphetamine (EMCDDA
list of ingredients (Burillo-Putze et al. 2011; Davies et al. 2007b; Staack 2007). Due to its legal status and possibil-
2010; EMCDDA 2010), adverse effects or provide safety ity of legitimate promotion, the spread potential of such
information like contraindications and possible drug–drug substances is greater than that for controlled substances
interactions (Burillo-Putze et al. 2011; Schmidt et al. 2011; (EMCDDA 2007b). A survey in United Kingdom, where
Zawilska 2011). In addition, “legal highs” are frequently 26 “legal highs” were purchased once a month over
advertised as “air fresheners,” “herbal incenses,” “bath 6 months (January 2009–June 2009) from five different
salts,” “plant fertilizers” and “not for human consump- Internet sites in United Kingdom, showed that piperazines
tion” (Elie et al. 2012; EMCDDA 2010; Zawilska 2011). were the most common psychoactive substance found in
Besides, it is reported the inconsistency and lack of homo- those tablets (Davies et al. 2010).
geneity in the composition of some “legal highs” sold over
the Internet (e.g., over time and between products sold by
different suppliers with the same name) (Baron et al. 2011; BZP development and therapeutic relevance
Davies et al. 2010; Ramsey et al. 2010) and on the other
hand, some products sold as “legal” in fact contain sub- Despite its synthetic origin, BZP was initially called and
stances already under control (Baron et al. 2011; Ramsey marketed over the Internet and by some retailers as a “natu-
et al. 2010), which increases the risk associated with the ral” product (“pepper extract” and/or “herbal high”) prob-
acquisition and use of such products. ably because of the structural similarity with piperidine, a
Most of these new psychoactive substances have gained component of the black pepper (Piper nigrum) (EMCDDA
popularity within the rave party scene particularly among 2007b; Johnstone et al. 2007).
young people as alternatives to illicit drugs (Berney-Meyer BZP was first developed, in 1944, as a potential antihel-
et al. 2012; Staack and Maurer 2005). Along with such minthic agent for livestock by Wellcome Research Labo-
recreational drugs, piperazine derivatives emerged in the ratories in the United Kingdom. However, because of its
1990s as a completely new class of designer drugs and safe lack of efficacy compared with piperazine and side effects
and legal alternatives to amphetamines (Staack and Mau- (namely seizures in mammals), it was never used for that
rer 2005). The first medical use of piperazine compounds purpose (Gee et al. 2005; Johnstone et al. 2007). Later, in
was as antihelminthic agents, in the 1950s, for the treat- the 1970s, it was evaluated, by the same laboratories, as a
ment of human and animal worm infections. After that, potential antidepressant agent due to its ability to reverse
several compounds with distinct pharmacological activi- the sedative effects of tetrabenazine (a dopamine-depleting
ties appeared on the market containing the piperazine moi- agent used for the treatment of involuntary hyperkinetic
ety, namely sildenafil and vardenafil (erectile dysfunction movement disorders such as Huntington’s disease) in rats
drugs), trazodone and nefazodone (antidepressant drugs), and mice (Antia 2009; Fantegrossi et al. 2005). However,
and clozapine and olanzapine (antipsychotic drugs) (Vorce it was never marketed as an antidepressant possibly due
et al. 2008). to its similarities with amphetamines, namely hyperactiv-
The piperazine derivatives have been shown to pos- ity and stereotypic behavior observed after its administra-
sess psychoactive properties and were promoted as rec- tion in animals (Johnstone et al. 2007; Perry 2008). Such
reational drugs. According to their chemical structure, amphetamine-like effects, both subjective and physiologi-
they can be divided into two classes: the benzyl- and the cal, were corroborated by in vivo studies in humans sug-
phenylpiperazines. The most common benzylpiperazines gesting that BZP has approximately 10 % the potency of
are N-benzylpiperazine (BZP) and 1-(3,4-methylenedi- dexamphetamine (Bye et al. 1973; Campbell et al. 1973).
oxybenzyl)piperazine (MDBP); the popular phenylpipera- The results of those investigations lead, for the first time,
zines are 1-(3-trifluoromethylphenyl)piperazine (TFMPP), to the recommendation that BZP should be under the same
1-(3-chlorophenyl)piperazine (mCPP), 1-(4-methoxy- regulatory measures applied to amphetamines due to its
phenyl)piperazine (MeOPP), 1-(4-chlorophenyl)pipera- potential of abuse (Campbell et al. 1973). In the 1980s,
zine (pCPP), and 1-(4-fluorophenyl)piperazine (pFPP) despite the previous findings and warnings, a derivative of
(Table 1) (Antia et al. 2010; Arbo et al. 2012; Peters et al. BZP, N-benzyl-piperazine-picolinyl fumarate (also known
2003; Staack 2007). These compounds were promoted and as piberaline or EGYT-475), was developed by researchers
sold, particularly via Internet websites, as free bases or salt at the Semmelweis University of Medicine in Hungary as
(de Boer et al. 2001), mainly as capsules, pills, tablets and an antidepressant (Schep et al. 2011; Sheridan et al. 2007).
powders (Gee et al. 2005; Staack 2007). Prior to legislative EGYT-475 was marketed as Trebilet®, but the revealed
13Arch Toxicol (2013) 87:929–947 931
Table 1 Chemical structures of piperazine designer drugs of abuse
Name Abbreviation Structure
N
1-benzylpiperazine BZP
NH
O
N
1-(3,4-methylenedioxy)benzylpiperazine MDBP NH
O
F NH
F
N
1-(3-trifluoromethylphenyl)piperazine TFMPP
F
N NH
1-(3-chlorophenyl)piperazine mCPP
Cl
1-(4-methoxyphenyl)piperazine MeOPP O N NH
H 3C
1-(4-chlorophenyl)piperazine pCPP Cl N NH
1-(4-fluorophenyl)piperazine pFPP F N NH
amphetamine-like properties made it unsuitable for thera- properties (Johnstone et al. 2007; Schep et al. 2011;
peutic purposes (Fantegrossi et al. 2005; Johnstone et al. Thompson et al. 2006). Literature also refers that, later,
2007), and it was withdrawn following phase II clinical tri- befuraline (DIV-145; 1-benzofuran-2-yl(4-benzylpiperazin-
als (Schep et al. 2011). Later, it was discovered in in vitro 1-yl)methanone), another BZP pro-drug, was developed
studies that EGYT-475 was a pro-drug and that BZP was and trialed as an antidepressant (Fig. 1). This compound
the active metabolite responsible for its antidepressant showed effectiveness similar to imipramine with fewer
Fig. 1 BZP (a) and its pro-
drugs EGYT-475 (b) and DIV-
145 (c)
13932 Arch Toxicol (2013) 87:929–947
side effects. Nevertheless, befuraline research appears to doping agent in horse racing (Kerr and Davis 2011) and by
have been discontinued after phase II clinical trials (Kerr athletes (Gee and Richardson 2005; Kerr and Davis 2011),
and Davis 2011). In synopsis, there are no licensed medi- where it is prohibited since January 1, 2007, by the World
cal products containing BZP in the European Union, and Anti-Doping Agency (WADA) (WADA 2006).
it is assumed that this substance has no therapeutic value Although being popular in many countries including the
(EMCDDA 2007a). USA, Australia, Sweden, Japan, South Africa and Bulgaria,
the drug only developed a significant market as a legal drug
in New Zealand since 2000 until 2008, as the main psy-
Physicochemical description and synthesis choactive constituent of “party pills” or “BZP-party pills”
(Cohen and Butler 2011), also known as “piperazine party
BZP, also known as 1-benzyl-1,4-diazacyclohexane or pills” (PPPs), “herbal highs” or “social tonics” (Gee and
N-benzylpiperazine, is a diamine with no stereoisomers Fountain 2007). In fact, in New Zealand, there were over
(EMCDDA 2007a). The substance is available as a free- 120 brands of party pills (Gee et al. 2008), and, in 2005, it
base or as a hydrochloride salt (BZP.2HC1). As a free base was estimated that approximately 150,000 doses of party
(CAS: 2759-28-6), it has a molecular formula of C11H16N2 pills were sold each month (Antia et al. 2009a). Accord-
and a molecular weight of 176.26 g/mol, and the hydro- ing to the literature, the New Zealand entrepreneur Matt
chloride salt (CAS: 5321-63-1) has a molecular formula of Bowden, a former methamphetamine addict, was responsi-
C11H16N2.2HCl and a molecular weight of 249.19 g/mol ble for the introduction of party pills in the market, in 1999.
(EMCDDA 2007b; Schep et al. 2011). In fact, Matt Bowden promoted BZP as a safer and legal
The base form is a pale, slightly yellowish-green viscous alternative to illicit drugs and referred a harm minimization
liquid (EMCDDA 2007a; Schep et al. 2011), which pre- role to this substance helping methamphetamine addicts to
sents an acidity constant (pKa) of 9.02 (20 °C) (Schep et al. overcome their addiction (Kerr and Davis 2011). This sub-
2011) and is corrosive. The hydrochloride salt is a white stance was legal in New Zealand up until 2008, and at this
solid, highly soluble in water, and irritant to eyes, respira- time, it was estimated that the party pill industry was worth
tory system and skin (EMCDDA 2007a; Schep et al. 2011). NZ$50 million (approximately 27 million euros) per year
BZP is readily synthesized by the reaction of piperazine (Cohen and Butler 2011), with the prevalence of the use
monohydrochloride and benzyl chloride, both easily avail- of BZP exceeding that of any other illicit drug, aside from
able chemicals. This synthesis is significantly easier com- cannabis, according to several surveys (Kerr and Davis
pared to other drugs such as amphetamine and ecstasy, and 2011).
it seems that dibenzylpiperazine (DBZP) may be formed Until 2005, there were no legal measures to control
during the reaction as an impurity (EMCDDA 2007a, b). BZP, although in that year, following a recommendation
from the Expert Advisory Committee on Drugs (EACD),
BZP was the first substance to be classified as a “restricted
BZP as a recreational drug substance” by the Misuse of Drugs Amendment Act 2005
(MDAA). At this point, BZP was made illegal to sell and
Legal status and evolution of the market supply to persons under the age of 18, and was also pro-
hibited the distribution of free samples besides television
In the 1970s and 1980s, several studies showed that BZP and print advertisement. Later, after the review of the epi-
has a stimulant amphetamine-like effect, and in the 1990s, demiologic and pharmacotoxicologic evidences, it was
the drug became popular as a recreational drug, being determined that BZP constituted a “moderate risk”, and
the major active ingredient of “party pills” (Johnstone on April 1, 2008, BZP and other related piperazines were
et al. 2007; Kerr and Davis 2011). The abuse of BZP was reclassified as Class C1 (similar to cannabis) and made
first described in the USA in 1996, in California (Austin illegal to manufacture, import, export, supply, sell and con-
and Monasterio 2004; Kerr and Davis 2011), although its sume by the MDAA 1975 (Cohen and Butler 2011; Kerr
use remained minimal until the end of the 90s when BZP and Davis 2011). It is referred that other legal drugs, such
started to spread particularly among youth as a legal rave/ as 1,3-dimethylamylamine (DMAA) (Bassindale 2011;
party drug (Kerr and Davis 2011), particularly due to its Cohen and Butler 2011), mephedrone and diphenylprolinol
promotion as “legal,” “natural” and “safe” (Gee et al. (D2PM), have taken much of the party pill market in this
2008). In fact, the promotion as “herbal pills” was per- country (Winstock and Ramsey 2010).
ceived, particularly among youth, as a weaker and safer Similar to what happened in New Zealand, BZP started
product due to its herbal origin unlike other synthetic “real to be placed under control around the world, namely in
drugs” (Sheridan and Butler 2007). Besides the use as a the USA (since 2002), Australia and Japan (since 2006)
recreational drug was also described the use of BZP as a (Cohen and Butler 2011).
13Arch Toxicol (2013) 87:929–947 933
The size of the BZP market beyond New Zealand is less presence of BZP and TFMPP, already under control, in
known, being reported sporadic seizures of BZP-party pills legal highs sold by UK online legal high retailers (Baron
in the European Union (Cohen and Butler 2011), where it et al. 2011; Davies et al. 2010). Furthermore, the combina-
was first noted as a drug of abuse in Sweden in 1999 (Wik- tion of different substances in powders and tablets, and also
strom et al. 2004). At this time, BZP was added to an early the combination of BZP and other piperazines with other
warning system designed to monitor new potential drugs of well-known drugs, such as amphetamine and ecstasy, is
abuse (Kerr and Davis 2011). However, its widespread as a partly responsible for the increasing difficulty in the inter-
recreational drug in Europe only occurred in the second half pretation of the seizures (EMCDDA 2010).
of 2004 (EMCDDA 2007a), and there has been an increase
in the number of notifications to the European Monitor- Patterns, prevalence and motivations of use
ing Centre for Drugs and Drug Addiction (EMCDDA) and
Europol relating to it by the end of 2006 (EMCDDA 2007c). Due to its legal widespread market in New Zealand, most
Between 2005 and 2007, formulations with BZP, mainly of the knowledge concerning the use of BZP-party pills
tablets and capsules, were extensively sold in smart shops, comes from this country. BZP is commonly swallowed in
through websites and even in music festivals (EMCDDA capsule or tablet form, although is also reported the snort-
2008). During this period, despite the lack of control, sei- ing of the powder as well as its mixture in drinks or swal-
zures of BZP in powder, capsule or tablets were reported in low wrapped in cigarette paper (“hummer”) (Butler and
13 EU Member States (including Belgium, Denmark, Fin- Sheridan 2007; Sheridan and Butler 2007; Wilkins et al.
land, France, Germany, Greece, Ireland, Malta, the Nether- 2006) and the intravenous (i.v.) use in an attempt to achieve
lands, Portugal, Spain, Sweden and the United Kingdom) a faster onset of action. The i.v. administration of BZP was
and in Norway (EMCDDA 2007a). The United Kingdom reported by the users as being painful due to the alkalinity
and Sweden were the two countries with the largest number of the solution (pH ≥12) (Gee et al. 2005).
and size of seizures (EMCDDA 2007a, c). Among tablets BZP was sold and consumed in products more com-
seized, the “Mitsubishi” and “Smiley Face” designs were monly known as “Legal X”, “Herbal ecstasy”, “Legal E”
common, which may explain the BZP seizures before any and “A2” (EMCDDA 2007a; Hill and Thomas 2009) and
regulation and the probable sale and acquisition of BZP, at was marketed under different brand names (for example,
least in part, as ecstasy (EMCDDA 2007a). In fact it was “P.E.P. pills”, “Jump”, “Euphoria”, “Rapture”, “Frenzy”
reported the acquisition of pills as being ecstasy pills when, and “Charge”) (Cohen and Butler 2011; EMCDDA 2007a;
in fact, they contained BZP (Wood et al. 2008). Wilkins et al. 2008).
The growing concerns around this psychoactive sub- With the increasing popularity of party pills, the com-
stance led to a formal request for risk assessment in 2007 bination of BZP with other psychoactive substances, such
(EMCDDA 2007c), although, at this time, some Member as other piperazines (mainly, TFMPP, mCPP and MeOPP),
States (Belgium, Denmark, Greece, Malta and Sweden) increased (Antia et al. 2009a; Schifano et al. 2006; Sheri-
already controlled BZP under drug control measures, dan et al. 2007), in addition to other ingredients like caf-
Spain and the Netherlands regulated BZP under medicine- feine, herbal extracts, amino acid and electrolyte blends, in
related legislation, and in Ireland, the sales were prohib- order to enhance its positive effects (Butler and Sheridan
ited to individuals under the age of 18 (EMCDDA 2007c). 2007; Nikolova and Danchev 2008; Sheridan et al. 2007) or
The BZP risk assessment reported the lack of information diminish the side effects (for example, l-tyrosine as a pre-
on the pharmacological and toxicological effects of such cursor of dopamine in order to ameliorate any dopamine
substance in humans, its activity as a central nervous sys- depletion due to the consumption of such pills) (Sheridan
tem stimulant (CNS) and the possible interindividual vari- et al. 2007). The combination of BZP with TFMPP was the
ability in the expression of its toxicity due to genetic poly- most popular combination of piperazines in party pills, and
morphisms in metabolizing enzymes and interactions with drug users reported the consumption of this combination
other drugs. Consequently, was recommended the estab- is an attempt to mimic the MDMA effects (Baumann et al.
lishment of appropriate control measures in the Member 2005; de Boer et al. 2001; Nikolova and Danchev 2008;
States (EMCDDA 2007a). Later, in March 2008 was pub- Staack 2007). In fact, the effects of TFMPP in the release of
lished the decision of the Council of Europe that all Mem- serotonin (5-HT) are suggested as being responsible for the
ber States should apply to BZP control measures within hallucinogenic effects attributable to pills containing such
1 year (EMCDDA 2008). mixture in addition to the stimulant and euphoric properties
Since this decision, the availability of BZP in Europe of BZP (Baumann et al. 2005; Yeap et al. 2010). Further-
appears to have decreased, although some Member more, in mice, the combination (BZP + TFMPP) has been
States continue to report its availability in 2009 and 2010 shown to have similar effects to MDMA in the release of
(EMCDDA 2010, 2011). In fact, some works reported the dopamine (DA) and 5-HT (Baumann et al. 2005). In these
13934 Arch Toxicol (2013) 87:929–947
pills, the ratio of BZP to TFMPP can range from 2:1 to 10:1 considerably between brands, the amount of BZP and other
(Lin et al. 2011a; Thompson et al. 2006). Is still referred its piperazines consumed depends not only on the number of
combination with other illicit substances such as ampheta- party pills taken but also the strength of such pills (Wilkins
mine, ecstasy, cocaine and ketamine, to enhance its stimu- et al. 2008). This high consumption may result in the exac-
lant and euphoric effects (EMCDDA 2007b; Staack 2007). erbation of toxicity and is in line with data from hospi-
Furthermore, nevertheless the advertising from the retailers talizations due to the intake of party pills (Gee et al. 2005).
to avoid the combination of party pills with alcohol, medi- Furthermore, it seems that this high consumption may be
cines and other drugs (Butler and Sheridan 2007; Ham- associated with the lack of the desired effect or time that is
mond 2008; Wilkins et al. 2006), surveys conducted in New needed to those effects occur (Butler and Sheridan 2007; Gee
Zealand found that most users of party pills consumed it in et al. 2005), as well as due to the promotion of such prod-
combination with other psychoactive substances, particu- ucts as “herbal” and legal, which leads the user to underesti-
larly alcohol, ecstasy, cannabis, amphetamines and nitrous mate the strength of the products (Gee et al. 2008; Sheridan
oxide (Butler and Sheridan 2007; Wilkins et al. 2006, 2008). and Butler 2010). The amount of party pills consumed also
Such surveys also revealed that the combinations of party seemed to depend on the places and context of use as well
pills with other substances often had specific roles, such as the negative effects (“hang-over”) already experienced
as (1) increase or extend the stimulant effects; (2) allow a by consumers. In fact, adverse effects are reported as one of
greater intake of alcohol since it is reported that party pills the main reasons leading to the decrease in the use of party
increase sobriety (Butler and Sheridan 2007; Wilkins et al. pills, in addition to changes in lifestyle, and seasonal varia-
2006); and (3) allow to deal with the negative effects of tions related to the recreational environments in which these
party pills (for example, cannabis to relax, stimulate appe- products are generally consumed (Butler and Sheridan 2007;
tite and sleep) (Butler and Sheridan 2007). Furthermore, the Wilkins et al. 2006).
so-called recovery pills were also used with this purpose. According to the studies performed in New Zealand, the
“Recovery pills” contain 5-hydroxytryptophan (5-HTP) and use of legal party pills was highest among youth and young
have been sold, sometimes in the same packs, and marketed adults (Butler and Sheridan 2007; Wilkins et al. 2006). A
as being able to reduce the adverse effects of party pills as it household survey, in 2006, revealed that, out of 2010 indi-
is converted to 5-HT in the brain (Wilkins et al. 2006, 2008). viduals, aged between 15 and 45 years old, the prevalence
Some authors also suggest that as BZP and 5-HTP increase of use was higher among those aged 18–29 years, with
the levels of 5-HT, it may increase the risk of adverse side almost 50 % of respondents between 20 and 24 years hav-
effects as happens with ecstasy (Wilkins et al. 2008). ing ever tried party pills (Wilkins et al. 2006). This survey,
The growing popularity as well as the emergence of sev- like others, showed that in almost all age groups, the use
eral brands was accompanied by an increase in the amount was greater among males than females (Butler and Sheri-
of BZP content (Gee et al. 2008; Hammond 2008; Thomp- dan 2007; Sheridan and Butler 2007; Wilkins et al. 2006).
son et al. 2006), with the typical dose of BZP ranging In addition, BZP-party pills users include both users
between 50 and 200 mg (Sheridan et al. 2007; Thompson of illicit drugs and legal substances from different social
et al. 2006; Wilkins et al. 2008). There are also references classes, being used in particular by high school and univer-
to party pills containing higher quantities, up to 1,000 mg, sity students as well as by part- or full-time workers (Butler
though it was not a common scenario (Gee et al. 2005, and Sheridan 2007; Sheridan and Butler 2007; Wilkins
2008). Some differences between what was labeled on the et al. 2006). Thus, unlike what occurs with the regular con-
packages have been detected, both in the qualitative (pip- sumers of other type of drugs, namely illicit drugs, BZP-
erazines present) and quantitative content (Kenyon et al. party pills consumers did not seem to arise from groups
2007; Thompson et al. 2006). socially and/or economically marginalized (Butler and
According to surveys conducted in New Zealand, the Sheridan 2007).
average amount of party pills consumed per occasion was The majority of the BZP-party pills users declared using
approximately 2 or 3, although there are reports of consump- BZP as a recreational drug due to its stimulant proprieties
tion of 8 or more pills (Butler and Sheridan 2007; Sheridan (increased confidence, talkativeness, euphoria, vigor and
and Butler 2007; Wilkins et al. 2006), exceeding what was activity, and enhanced socialization) (Butler and Sheri-
usually recommended by manufacturers (“2, wait 2 h, then dan 2007; Wilkins et al. 2006; Zawilska 2011), mainly at
another 2 if tolerated”) (Thompson et al. 2006). A survey night and weekends at dance parties or raves (Butler and
(n = 189) performed by Wilkins et al. (2008) revealed that Sheridan 2007; Johnstone et al. 2007). The studies also
the amounts of piperazine (BZP/TFMPP) taken on an occa- highlighted the similarities between the use of BZP-party
sion of greatest use ranged between 43 and 2,500 mg, with pills and ecstasy, particularly the use of other drugs and
the highest amount of participants having consumed between extended periods of dancing in heated environments (Butler
100 and 500 mg. As the amount of BZP in party pills varies and Sheridan 2007; Cohen and Butler 2011). Besides the
13Arch Toxicol (2013) 87:929–947 935
recreational use of such drug, a more functional use is also from BZP use to illegal drugs, to other legal substances
reported as a means of increasing alertness and physical/ with unknown toxicity and/or to an increased criminali-
mental performance among students and workers (such as zation around BZP-party pills (Bryson and Wilson 2007;
shift workers and truck drivers) (Butler and Sheridan 2007; Cohen and Butler 2011; Green 2008).
Cohen and Butler 2011). Other less common uses were also Apart from BZP criminalization, other factors men-
reported as, for example, the use by young females as an tioned by users as being important reasons for stopping
appetite suppressant for weight loss (Wilkins et al. 2006). BZP use both before and after the criminalization were the
hangover effects and physical health reasons (Wilkins et al.
Impact of the legal status on the consumption of BZP 2006; Wilkins and Sweetsur 2012).
The legal status of BZP affected its use, particularly among Health issues related to BZP use
young people (Sheridan and Butler 2010; Wilkins et al.
2006). In fact, a study performed by Sheridan and Butler Despite the misconception that BZP-party pills are safe,
(2010), in New Zealand, showed that because BZP-party there are a number of case reports and clinical evidence
pills were legal, the users (n = 58, aged between 17 and supporting its toxicity, which is expected to be due to the
23 years) had the perception that they were safe compared similarities of this substance with amphetamines (Staack
with illicit substances. Furthermore, many believed that the 2007). Again, due to the more expressive market of this
legality of these products safeguard their quality, unaware substance, the clinical experience of piperazines toxicity
that there were no controls in the manufacturing process. in New Zealand is probably the greatest (Bassindale 2011;
The presence of labels in the products also carried the per- Hill and Thomas 2009). The adverse physical symptoms
ception of quality and purity and confidence that they were most frequently reported by users are as follows: insomnia,
consuming exactly what they bought, despite the lack of headaches and nauseas (Kerr and Davis 2011; Wilkins et al.
any kind of assessment to which the products were sub- 2006). Other negative effects reported include the following:
jected in order to prove the veracity of the information on dizziness, mood swings, agitation, strange thoughts, tremor,
the label. With respect to the strength of such pills, many diaphoresis, dehydration, urine retention, xerostomia, tachy-
respondents said that they expected that as these products cardia, hypertension, bruxism and trismus, mydriasis, loss
were legal, the psychoactive effects were moderate. Addi- of appetite, and tiredness, some of which appeared to per-
tionally, the legality provided an easier access to these sist for more than 24 h after ingestion (Butler and Sheridan
products and the lack of criminal behavior unlike what hap- 2007; Gee et al. 2005; Wilkins et al. 2006).
pens with illicit drugs (Sheridan and Butler 2010). Some more serious adverse effects have also been
In conclusion, the legal status conveyed the perception reported, namely metabolic and respiratory acidosis,
of quality, safety, lack of criminal activity and expectation hyponatremia, toxic seizures (Gee et al. 2005; Wood et al.
that the psychoactive effects were relatively mild. Further- 2007), acute paranoid psychosis (Austin and Monasterio
more, being legal, these products were widely available and 2004), dissociative states (Wood et al. 2008), exacerbation
socially accepted/legitimate to use (Sheridan and Butler of mental illness (Mohandas and Vecchio 2008), hyperther-
2010). All these factors with their promotion as a legal and mia, rhabdomyolysis, disseminated intravascular coagula-
safe alternative to other drugs were motivating factors for tion, acute renal injury and multiple organ failure (Alansari
BZP-party pills consumption (Sheridan and Butler 2010). and Hamilton 2006; Berney-Meyer et al. 2012; Gee et al.
According to that, BZP-party pills, while legal, may act 2008, 2010). The dissociative symptoms have been noted
both as a “gateway” to illicit substances or as a harm reduc- in patients where the combination of BZP and TFMPP
tion “player” with illegal drug users taking BZP instead of was proven by serum analysis (Wood et al. 2008). Overall,
illicit drugs (Cohen and Butler 2011; Sheridan et al. 2007; according to data available from clinical and users reports,
Wilkins et al. 2006). Nevertheless, the real impact of BZP- most of the symptoms are characteristic of a sympathomi-
party pills legality and prohibition in the consumption of metic toxidrome similar to amphetamines and other sympa-
illegal drugs is not conclusive (Cohen and Butler 2011; thomimetics (Elliott 2011; Schep et al. 2011).
Wilkins and Sweetsur 2012) and might be both positive BZP had also been related to fatalities and detected in
and negative. In fact, on the one hand, its criminalization post mortem samples, namely from road traffic accidents
appears to have led to its decreased availability and con- (Balmelli et al. 2001; Elliott 2011; Elliott and Smith 2008; Hill
sumption (Kerr and Davis 2011; Sheridan et al. 2009; and Thomas 2011; Schep et al. 2011; Wikstrom et al. 2004),
Wilkins and Sweetsur 2012) both among general popula- although the role of BZP in the poisonings and deaths reported
tion and frequent drug users (Wilkins and Sweetsur 2012), is difficult to evaluate due to its common use in combination
but on the other hand, its ban from the legal market and as with other substances (Cohen and Butler 2011; Staack 2007).
a legal alternative to other drugs might conduct to a shift Secondly, the fact that many clinicians were not aware of this
13936 Arch Toxicol (2013) 87:929–947
substance, the similarities in the patterns of distribution and presynaptic α2-adrenoreceptors (Magyar et al. 1986). The
pharmacological effects with amphetamines, and the absence first effects of BZP on serotonergic neurotransmission are
of screening tests for BZP and other new designer drugs in also reported to the pharmacological assessment of piber-
clinical practice can lead to the underestimation of the role of aline, and it was concluded, during these studies, that BZP
such substances in poisonings (Staack 2007). Furthermore, blocks the reuptake of 5-HT in rats and has 5-HT1 receptor
despite being accepted that higher plasma levels of BZP are agonistic effects, mechanisms responsible for the central
related to an increased incidence of more severe side effects, serotoninomimetic action. Those studies have also shown
such as seizures (Gee et al. 2008), serum or urine concentra- that BZP had no effect on 5-HT2 receptors (Elliott 2011;
tions may not correlate with the severity of clinical symptoms. Staack et al. 2002). Some other studies also suggested that
In fact, toxicity seems to be unpredictable with some users BZP has 5-HT antagonistic properties due to its ability to
expressing significant toxic effects even after the ingestion antagonize 5-HT-induced contractions of rat stomach fun-
of “recommended” doses, suggesting the possibility of a nar- dus, and partial agonistic properties as it induced hyper-
row safety margin and interindividual pharmacokinetic vari- thermia in rats, effect reversed by cyproheptadine, a 5-HT
ation due to genetic polymorphisms and/or drug–drug inter- antagonist (Fantegrossi et al. 2005). It was suggested that
actions (Berney-Meyer et al. 2012; Gee et al. 2008; Schep those effects on serotonergic neurotransmission may be
et al. 2011). Furthermore, the environment of the rave party responsible for, at least, some of BZPs side effects, such as
(heat, increased physical activity, lack of sleep, dehydration, headaches and nausea (Nikolova and Danchev 2008).
excessive fluid ingestion and co-ingestion of other psycho- In a more recent work, Baumann et al. (2004) evaluated
active substances) also contributes to the toxicity associated the neurochemical effects of BZP, MDMA and TFMPP
with BZP-party pills intake (Berney-Meyer et al. 2012). In on transporter-mediated efflux of [3H]5-HT (serotonin
fact, the excessive and prolongated physical activity and/or transporter (SERT) substrate) and [3H]MPP+ (DA trans-
hyperthermia associated with rave parties may lead or con- porter (DAT) substrate) in rat synaptosomes. Additionally,
tribute to some of these effects, namely respiratory or meta- they evaluated the effects of such drugs on the extracel-
bolic acidosis, rhabdomyolysis, renal failure and disseminated lular levels of 5-HT and DA using in vivo microdialysis
intravascular coagulation. Furthermore, seizures, in turn, when in rats. According to their in vitro findings, BZP evokes
prolongated may also lead to the development of such toxicity DAT-dependent release of [3H]MPP+ but showed no effect
(Schep et al. 2011). Women also seem to be at a higher risk on the release of [3H]5-HT mediated by SERT (unlike
due to their smaller body size compared to men (Gee et al. MDMA and TFMPP). Furthermore, the effect of BZP on
2008; Wilkins et al. 2008). DA release was antagonized by low doses of DAT-selective
There is limited information on the long-term effects of blocker. The in vivo studies showed that BZP has the abil-
BZP intake, namely its potential to induce addiction, toler- ity to elevate the extracellular levels of both DA and 5-HT
ance or organic sequelae (Schep et al. 2011). in a dose-dependent fashion, being prevalent the effects
There are no specific treatment guidelines to BZP toxic- over DA, and about threefold less potent than MDMA. The
ity, and the management of patients consists in their stabi- mixture of BZP and TFMPP (1:1 ratio) resulted in dramatic
lization and supportive and symptomatic care. Depending dose-related increases in dialysate DA and 5-HT, suggest-
on the symptoms, the management may include the correc- ing a synergistic effect on DA (at the higher dose 10 mg/
tion of hyponatremia, hyperthermia, tachycardia, dehydra- kg) and additive effect on 5-HT. Such effects on monoam-
tion, hypertension, acid–base disturbances, and monitor of ines neurotransmission may explain the MDMA-like prop-
renal, muscular, cardiovascular and hepatic functions. The erties reported to the combination of such piperazines as
treatment of seizures and psychotic states may require the they mimic the known molecular mechanism of MDMA.
use of benzodiazepines and antipsychotics (Gee et al. 2005; In vitro, no interactions between the two drugs were noted,
Schep et al. 2011). suggesting a possible pharmacokinetic nature for the in
vivo synergism reported (Baumann et al. 2004; Baumann
et al. 2005). Lastly, Nagai et al. (2007), using rat brain syn-
Pharmacodynamics aptosomes showed that BZP strongly inhibits the reuptake
of DA and NA and has a smaller effect on 5-HT reuptake.
Neuropharmacology Furthermore, BZP also showed a monoamine-releasing
activity, particularly on DA and NA (Nagai et al. 2007).
During the assessment of piberaline, Magyar et al. (1986) In synopsis, similar to what occurs for other drugs of abuse,
found that its metabolite, BZP, had the ability to potenti- in vitro and in vivo studies have demonstrated that BZP inter-
ate the release of 3H-noradrenaline (3H-NA) from rabbit feres with monoaminergic neurotransmission, both inhibiting
pulmonary artery, being this effect inhibited by the admin- the reuptake and stimulating the release of DA, 5-HT and NA,
istration of 1-NA and clonidine, preferential agonists of predominating the effects on dopaminergic neurotransmission.
13Arch Toxicol (2013) 87:929–947 937
Behavioral and physiological studies in animals in fact during Meririnne et al. (2006) experiments, a DA
D1-like receptor antagonist attenuated BZP-induced place
The first behavioral effects of BZP were reported during preference. Furthermore, the involvement of serotonergic
the assessment as an antidepressant in rats. The studies system was also suggested as a 5-HT3 receptor antago-
showed that BZP induces hyperactivity, involuntary head nist also attenuated the BZP-induced place preference
movements and reduces the reaction time in shock avoid- response (Meririnne et al. 2006). In conclusion, similar to
ance studies, similar to dexamphetamine (Campbell et al. other drugs of abuse, BZP induces conditioned place pref-
1973). More recent works, in mice and rats, corroborated erence, showing discriminative stimulus properties similar
these first findings highlighting the powerful locomotor to amphetamine and reinforcing effects similar to cocaine.
stimulant effects of BZP (i.p. administrations with doses These findings in animals corroborated previous evidence
ranging from 5 to 100 mg/kg), showing that this compound in humans that suggested that BZP has abuse liability.
produces a dose-dependent increase in ambulation and ste- When assessing the similarities in acute effects on anx-
reotypy (Baumann et al. 2004; Brennan et al. 2007; Her- iety-related behavior between BZP (10 or 20 mg/kg) and
bert and Hughes 2009; Yarosh et al. 2007). The only avail- methamphetamine (1 or 2 mg/kg) in hooded rats, it was
able studies with primates (rhesus monkeys) also reported not clear whether the altered behavior of rats was due to
behavioral effects, such as hyperactivity, involuntary head an increased anxiety induced by the drug or to an increased
movements, jaw chattering, bizarre body postures and “fly stereotypy that interfered with the action of the drug (Her-
catching” (Fantegrossi et al. 2005). bert and Hughes 2009). However, despite the little conclu-
The assessment of the effects derived from chronic expo- sive evidence for anxiogenic effects of BZP, its anxiogenic
sure showed that repeated exposure to BZP (20 mg/kg) potential should not be overlooked as increased anxiety has
induces sensitization and cross-sensitization to metham- been reported by BZP-party pills users (Gee et al. 2005;
phetamine, measured as increases in hyperactivity (Bren- Wilkins et al. 2006).
nan et al. 2007). These acute and sensitized behavioral Due to BZP similarities with other drugs possessing sero-
responses that have been related to increases in the dopa- tonergic and dopaminergic agonist properties about which is
minergic neurotransmission (as increases in dialysate levels known to interfere with the normal neuronal development and
of DA) were dose-dependent and shown a positive correla- produce cognitive and mood deficits (Aitchison and Hughes
tion with increases in locomotor activity and stereotypical 2006), the possible long-term effects resulting from the expo-
movements (Baumann et al. 2004; Brennan et al. 2007). sition to BZP during adolescence were also evaluated. A pre-
Furthermore, stereotypy and hyperactivity have been related liminary study performed by Aitchison and Hughes (2006)
to increases in nigrostriatal and mesolimbic dopaminergic in rats evaluated the behavioral consequences following the
neurotransmission, respectively. Changes and adaptations administration of BZP (10 mg/kg/day, i.p.) during P45–P55
in the dopaminergic neurotransmission induced by chronic (equivalent of late human adolescence to early adulthood),
exposition to BZP were also suggested as being implicated with particularly attention to its anxiogenic potential and
in the sensitization and cross-sensitization, similar to what sex-related differences. From the results (decreased social
have been suggested to other stimulant drugs (Brennan et al. interactions, responsiveness to brightness change, and emer-
2007). Thus, BZP may induce neuroadaptations that sensi- gence from the dark into the light) of this study, it was sug-
tize users to other drugs and potentially act as a “gateway gested the possibility of BZP interferes with the development
drug” to other more harmful drugs (Brennan et al. 2007). of anxiety-related mechanisms operated by 5-HT, resulting
The rewarding properties of BZP were evaluated using in increased levels of anxiety in adulthood. Yet, even due to
self-administration (Fantegrossi et al. 2005), discriminative more pronounced effects of BZP on dopaminergic system,
(Fantegrossi et al. 2005; Yarosh et al. 2007) and place pref- it was also referred that the behavioral effects observed may
erence methods (Meririnne et al. 2006). Fantegrossi et al. be related to the depletion of DA, and thus, the decreased
(2005) showed that BZP induces intravenous self-adminis- motor activity can be a result of BZP exposure (Aitchison
tration in animals (rhesus monkeys) trained to self-admin- and Hughes 2006). In fact, abnormal dopaminergic activity
ister cocaine and possesses discriminative responses simi- has been associated with deficits in motor control and aggres-
lar to amphetamine (Fantegrossi et al. 2005). In rats, BZP siveness. Additionally, a recent work assessed the long-term
induced conditioned place preference in a dose-depend- effects (in the periods P78–81 and P117–120) resulting from
ent manner (Meririnne et al. 2006) and, in mice, induced the exposure to BZP (10 mg/kg/day, i.p.) and/or ethanol
MDMA-like discriminative stimulus without inducing head (2 g/kg/day, i.p.) during adolescence (P41–50), and there
twitch behavior (used to assess hallucinogen-like actions) were no statistically significant differences between treated
(Yarosh et al. 2007). DA neurotransmission at the mesolim- animals and controls (Perry 2008). Nevertheless, these non-
bic system has been implicated in the rewarding proper- consistent results highlighted that BZP exposure, particularly
ties of several other psychoactive drugs (Perry 2008), and during adolescence, can have long-term outcomes.
13938 Arch Toxicol (2013) 87:929–947
In the literature, it is also cited that BZP induces hyper- blood pressure (systolic and diastolic), pupillary dilata-
thermia when administered to rats at an ambient tem- tion (when administered as eye drops), improvements in
perature of 28 °C (Horai et al. 2010). This effect has been the test of auditory vigilance and stimulant activity. The
related with the action of 5-HT on the thermoregulatory stimulant activity was similar and only detected when
center within the hypothalamus and is probably directly volunteers received the highest doses tested, 100 mg BZP
related with the dose and the room temperature as seen or 7.5 mg dexamphetamine (Campbell et al. 1973; Elliott
with other drugs with hyperthermic and hypothermic 2011). Another study, performed by Campbell et al. (1973)
effects (Lin et al. 2009, 2011b) in former amphetamine-type addicts, compared the sub-
jective and physiological effects of BZP (BZP hydrochlo-
Combination with other substances ride, 100 mg), dexamphetamine (dexamphetamine sulfate,
10 mg) and a lactose control, in double-blind conditions.
Due to the frequent combination of BZP with other sub- Observations of pulse rate, blood pressure, pupil size and
stances by users, the assessment of the effects of these mental/mood status were made and repeated at 1, 2 and
combinations is essential to assess the safety of BZP, 3 h after their administration. Both dexamphetamine and
given that resembles the real context associated with their BZP caused increases on pulse rate and blood pressure,
consumption. as seen in previous studies. BZP also produced pupillary
During the study of Baumann et al. (2004), it was noted dilatation (not noted with dexamphetamine), sweating and
that, in contrast with BZP, the mixture of BZP plus TFMPP flushing. The subjective effects were indistinguishable with
(1:1) did not produce robust locomotor stimulation, and at both drugs being considered desirable, and BZP was scored
the high dose (10 mg/kg, i.v.), the motor stimulant effects by many better than dexamphetamine in terms of subjec-
were suppressed with several rats developing seizures and tive drug liking. Overall, these studies concluded that BZP
ataxia. Despite the seizures were short-lived and all ani- has a stimulant activity similar to dexamphetamine, but an
mals recovered completely, the dose which caused these effective potency about tenfold lower (de Boer et al. 2001;
effects (10 mg/kg BZP + 10 mg/kg TFMPP, i.v.) was only Elliott 2011).
about three times higher than that required for observable In a recent, randomized, double-blind, placebo-con-
effects on monoaminergic neurotransmission, which sug- trolled study, the physiological and subjective effects of
gests a narrow window of safety. It has been suggested that BZP (200 mg in a single oral dose) were evaluated in 27
the suppression of BZP psychomotor properties by TFMPP human females. It was again noted that BZP significantly
is due to its properties at a postsynaptic level on serotoner- increases blood pressure and heart rate and has stimulant
gic neurotransmission (Baumann et al. 2004, 2005). effects, increasing euphoria, dysphoria (maybe related with
The reinforcing properties of the mixture were also a rebound effect), sociability and drug liking. A decrease in
evaluated in rhesus monkeys, and the reinforcing effects of body temperature was also recorded after administration of
BZP when combined with TFMPP were less pronounced BZP when compared to placebo, suggesting that the room
than with BZP alone, decreasing with the increase in the temperature might not be high enough to induce hyperther-
concentration of TFMPP. In this same study, TFMPP alone mia (Lin et al. 2009).
had not discriminative nor self-administration properties. The cardiovascular effects have been attributed to the
These results were in accordance with those observed with peripheral sympathomimetic action of BZP, while the stim-
other hallucinogenic drugs, being suggested that agonistic ulant and subjective effects are attributed to the stimulation
action at 5-HT2c receptors suppresses dopaminergic activ- of dopaminergic and serotonergic neurotransmission at a
ity at the mesolimbic system (Fantegrossi et al. 2005). central level (Lin et al. 2009; Thompson et al. 2006).
Perry (2008) also evaluated the long-term effects of the
exposure to BZP in combination with alcohol during ado- Combination with other substances
lescence in rats without, however, showing statistically
significant differences between the three groups (animals The physiological and subjective effects of BZP (100 mg)
treated with BZP; BZP + ethanol; ethanol) (Perry 2008). in combination with TFMPP (30 mg) were also determined
in human males. Similar to what was observed with BZP
Human studies alone, the combination significantly increases blood pres-
sure (both diastolic and systolic) and heart rate, without
Similarities between BZP and dexamphetamine were visible changes in body temperature. According to the sub-
reported in humans (with no previous experience on jective rating scales, the combination has similarities with
amphetamines) in 1971 and 1973 with doses ranging from other commonly known stimulants producing dexampheta-
20 to 100 mg (Bye et al. 1973; Campbell et al. 1973). mine and MDMA-like effects, increasing dysphoria and
Both compounds produced increases on heart rate and self-confidence (Lin et al. 2011a, b).
13Arch Toxicol (2013) 87:929–947 939
Another randomized, double-blind, placebo-con- instructions”, carries a significant risk of severe adverse
trolled study performed in New Zealand by Thomp- events (Thompson et al. 2006).
son et al. (2006) evaluated the safety of four treat-
ments: (1) BZP + TFMPP (300 mg/74 mg) and placebo;
BZP + TFMPP (300 mg/74 mg) and 57.6 g alcohol; (3) Pharmacokinetics
placebo and 57.6 g alcohol; and (4) double placebo. BZP
and TFMPP were administered in two doses within a 2-h Metabolic pathways
interval and the total amount of alcohol was ingested in
six doses. The cardiovascular and psychological effects, The pharmacokinetics of BZP is not yet fully elucidated; in
delayed effects on sleep, adverse events and the effects on fact, there is few published information about its absorption
a driving performance test were evaluated for all groups and distribution, both in humans and animals.
under study. This study showed more reliability with the The metabolism of BZP was first studied by Staack et al.
recreational use of party pills, not only due to the com- (2002) in Wistar rat urine after a single dose of 50 mg/kg
bination of piperazines but also for its combination with by gastric intubation, and the results were compared with
alcohol and the use of party pills commercially available human urine samples. According to the metabolites iden-
instead of pure isolated compounds. The study was stopped tified, it has been proposed that BZP undergoes hydroxy-
earlier when only 35 of the planned 64 subjects had been lation and dealkylation as phase I reactions and has three
included in the trial due to the emergence of severe adverse metabolic targets: the aromatic ring, the benzyl carbon
effects (such as agitation, anxiety, hallucinations, vomit- and the piperazine moiety. The aromatic ring is altered
ing, migraine and insomnia). Those events were reported by single aromatic hydroxylation to form 4-hydroxy-BZP
in 4/10 subjects who received the combination of pipera- (4-OH-BZP; p-OH-BZP), 3-hydroxy-BZP (3-OH-BZP;
zines and in 3/7 subjects who received this combination m-OHBZP) and double aromatic hydroxylation followed
and alcohol. Apart from these adverse effects, the combina- by methylation to form 4-hydroxy-3-methoxy-BZP (4-OH-
tion of piperazines, with or without alcohol, caused marked 3-OCH3-BZP). Furthermore, metabolic dealkylation at the
increases on blood pressure, heart rate and difficulty in get- benzyl carbon and piperazine moiety leads to the formation
ting to sleep. BZP and TFMPP combined also resulted in of piperazine, benzylamine and N-benzylethylenediamine
significant improvements in the driving performance test (Fig. 2). From the dealkylation at the benzyl carbon, it
even in combination with alcohol (alone affected negatively was also suggested the formation of benzaldehyde which
the driving performance). Overall, the results of this study can be further oxidized to benzoic acid; however, as ben-
showed that BZP + TFMPP alone or in combination with zoic acid is ubiquitous in rat urine, the formation of such
alcohol, even when consumed according to “manufacturer’s a metabolite cannot be confirmed (Staack et al. 2002). The
NH
N
Aromatic
hydroxylation Dealkylation HN
NH
HO (2) (5)
HO NH2
N N
CYP 450
NH NH
CYP 450
(3) (1) (6) NH2
NH
SULT; UGT
CYP 450
Glucuronide or sulfate
conjugates
HO
N (7)
NH
HO
COMT
O
H3C N
NH
HO
(4)
Fig. 2 Metabolic pathways for BZP in rats and humans. The bold BZP, (3) 3-OH-BZP, (4) 4-OH-3-OCH3-BZP, (5) piperazine, (6)
arrows represent the metabolic pathways suggested as being domi- benzylamine and (7) N-benzylethylenediamine (adapted from Staack
nant. The compounds identified are as follows: (1) BZP, (2) 4-OH- et al. 2002)
13940 Arch Toxicol (2013) 87:929–947
hydroxylated compounds can still enter phase II reactions the first 48 h of BZP and its major urinary metabolites
being partially eliminated as sulfate or glucuronide conju- (4-OH-BZP and 3-OH-BZP), following a single i.p. dose
gates (Maurer et al. 2004; Staack et al. 2002; Staack and of 5 mg/kg BZP. The study showed that, within 48 h,
Maurer 2005). The first study on the pharmacokinetics of approximately 25 % of BZP was eliminated as 4-OH-BZP
BZP in humans also suggested the formation of BZP conju- and only 2 % as 3-OH-BZP, and 6.7 % dose of BZP was
gates with sulfates (Antia et al. 2009b). excreted unchanged. Almost 50 % of metabolites were
According to the metabolites identified, the enzymes eliminated as glucuronide conjugates and lesser as sulfate
that have been proposed as being involved in BZP metabo- conjugates. The ratio of 4-OH-BZP/3-OH-BZP increased
lism are as follows: cytochrome P450 (CYP) which cata- with time suggesting a preference for the formation of the
lyzes phase I reactions (hydroxylations and dealkylations) p-hydroxylated metabolite over time. The urinary peak of
(Antia et al. 2009a; Yeap et al. 2010), catechol-O-methyl- BZP was observed at about 4 h postdosing (undetectable
transferase (COMT) that catalyzes the methylation of the 48 h postdosing), while metabolites peaked approximately
dihydroxy metabolite (Staack et al. 2002; Tsutsumi et al. 8 h postdosing and were detectable up to 48 h postdos-
2006), sulfotransferase (SULT) and uridine diphosphate ing. In resume, 4-OH-BZP was found as the main urinary
glucuronyltransferase (UDP-glucuronosyltransferase; UGT) BZP metabolite in rats corroborating what was reported by
responsible for the formation of sulfate and glucuronide Staack et al. (2002). After 48 h, approximately 33 % of the
conjugates, respectively (Jancova et al. 2010). dose administered was eliminated (about 20 % unchanged
In addition to the factors previously mentioned as pos- and 80 % as its main metabolites), unlike what was
sibly implied in BZP unpredictable toxicity (such as drug– described by Staack et al. (2002) where BZP was excreted
drug interactions and environmental factors), the occurrence mainly unchanged in urine (Tsutsumi et al. 2006). Despite
of genetic enzymatic polymorphisms may also contribute these discordant results, given that the animals belong to
to its interindividual variability, as there are well-known the same species, it is necessary to take into considera-
polymorphisms for the enzymes involved either in phase I tion that the dosages and routes of administration were
(particularly CYP 2D6) or in phase II (COMT, SULTs and different.
UGTs) metabolic reactions (Antia 2009; Antia et al. 2009a). An unpublished work made by Chou et al. (2008) at
University of Auckland with Sprague–Dawley rats, after a
In vitro studies single i.p. dose of 1 mg/kg, evaluated the tissue disposition
of BZP and its main metabolites (4-OH-BZP and 3-OH-
Considering that the dealkylation and hydroxylation path- BZP) 30 and 60 min postdosing. According to this work,
ways are dependent on the action of CYP enzymes, it was BZP appears to be rapidly metabolized and distributed to
studied the involvement of five CYP isoforms (CYP 2D6, tissues, with kidneys being the organ displaying the high-
1A2, 3A4, 2C9, and 2C19) in BZP metabolism, using est concentration of BZP and liver displaying the major
pooled human liver microsomes to minimize the effect of concentrations of 3-OH-BZP and 4-OH-BZP (Chou et al.
interindividual variability and selective inhibitors of specific 2008). This explain, at least in part, the preliminary results
CYP isoforms. This study showed that, when incubated with reported by Cole (2011) which refers that BZP is extremely
specific inhibitors of CYP 1A2, 3A4 and 2D6 isoforms, the toxic to both liver and kidney cell lines, as well as the
metabolism of BZP was significantly inhibited, highlighting symptoms of renal and hepatic failure reported in some of
the involvement of such isoenzymes in the hepatic metabo- BZP users (Cole 2011).
lism of BZP in humans. The inhibition increased in the fol- More recently, Wada et al. (2012) performed a study in
lowing order: CYP 2D6 (28 %) < CYP 3A4 (54 %) < CYP order to evaluate the pharmacokinetics of BZP and TFMPP
1A2 (74 %). In contrast, the inhibitors of CYP 2C9 and after their sole or coadministration (2 mg/kg, i.p.) to rats.
2C19 did not affect the metabolism of BZP (Antia 2009; Plasma samples were collected for 480 min after adminis-
Antia et al. 2009c). Inhibition of CYP 3A4- and 1A2-medi- tration (limit of detection = 0.9 ng/mL). The overall mean
ated metabolism appeared to be concentration-dependent, clearance of BZP was found to be 0.017 ± 0.0038 L/min,
but in contrast, for CYP 2D6, the inhibition did not appear the mean volume of distribution was 5.1 ± 2.1 L, mean
to be dependent on the concentration of BZP (Antia 2009). elimination rate constant was 0.0037 ± 0.0016/min, mean
elimination half-life 219 ± 108 min, and the mean area
In vivo studies under the curve was 22 ± 5.1 min mg/mL.
Animals studies Human studies
Tsutsumi et al. (2006) studied the metabolism of BZP The only available pharmacokinetic study in humans
in Wistar rat by analyzing the excretion profile within reported the plasma concentrations of BZP, 4-OH-BZP and
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