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Rationale: ‘Party Pills’ containing benzylpiperazine (BZP) and trifluoromethylphenylpiperazine (TFMPP) have been used in a recreational context since the 1990s and, prior to April 2008, were legally available in New Zealand. Taken together, they have been reported to produce a ‘high’ similar to that produced by 3,4-methylenedioxymethamphetamine (MDMA)., Objectives: There has been little research on the subjective effects of piperazines in humans. The purpose of this study is to further investigate the subjective and physiological responses following an oral dose of BZP combined with TFMPP in males., Methods: In a randomised, double-blind, placebo-controlled study the subjective and physiological effects of BZP/TFMPP were investigated in 36 healthy, non-smoking males (mean age 22 ± 4 years). Participants were tested before and approximately 120 min after administration of a single dose of placebo (n = 16) or 100/30 mg BZP/TFMPP (n = 20). Participants were required to comment on the subjective effects using three rating scales—the Addiction Research Centre Inventory (ARCI), the Visual Analogue Scale (VAS) and the Profile of Mood States (POMS). Participants' blood pressure, heart rate and body temperature were also measured., Results: Statistical analysis using repeated-measures analysis of variance (ANOVA) and planned comparisons revealed that BZP/TFMPP significantly increases blood pressure and heart rate (p < 0.05). Likewise, the subjective rating scales revealed that BZP/TFMPP has significant dexamphetamine-like effects, increases dysphoria and feelings of self-confidence (p < 0.05)., Conclusion: These physiological and subjective data reflect clear similarities between the effects of BZP/TFMPP and commonly known stimulants such as dexamphetamine and MDMA.

BZP and TFMPP are amphetamine-like recreational drugs and the major active components of 'party pills'. The pharmacodynamic effects of these neurally active drugs are thought to be dependent on their activity at DA and 5-HT receptors and several studies report drug-drug interactions at a pharmacodynamic level. Their metabolism involves the hepatic P450 enzymes CYP2D6, CYP1A2 and CYP3A4 resulting in inhibited metabolism of other drugs and medicines, as well as compromised metabolism in poor metabolisers for CYP2D6. Basic pharmacokinetic properties are described for both BZP and TFMPP when taken alone and in combination. Several studies have shown that these drugs cause several drug-drug interactions.

Aim: This study explores potential drug-drug interactions between BZP and TFMPP. This was achieved by comparing the metabolism and pharmacokinetics of BZP and TFMPP when taken together with previously published data on their individual metabolism and pharmacokinetics., Method: Blood and urine samples were collected from seven participants given a combined dose of BZP (100 mg) and TFMPP (30 mg) and analysed by LC-MS in order to quantify the concentrations of BZP, TFMPP, and their major hydroxylated metabolites 3-OH BZP, 4-OH BZP, and 4-OH TFMPP., Results: The metabolic profiles of both drugs were altered when co-administered. Both BZP and TFMPP lost one metabolite, 3-OH BZP and 4-OH TFMPP, respectively. Some differences in the pharmacokinetic properties of TFMPP were also noted., Conclusion: Metabolic interactions between BZP and TFMPP are clearly observed in this study along with some changes to the pharmacokinetics of TFMPP. As these drugs are often co-administered, the interactions between them are both relevant and concerning. Awareness of these interactions can assist clinicians in understanding toxicities relating to the co-administration of BZP and TFMPP or other party pill drugs.