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Rationale: The use of synthetic cathinones as recreational drugs frequently sold in combination has been increasing exponentially. However, the consequences of combining cathinones on the resulting stimulant effects and the pharmacokinetics have been poorly investigated. Objective and methods: To study 3,4-methylenedioxypyrovalerone (MDPV; 3?mg/kg) and mephedrone (4-MMC; 30?mg/kg)-induced effects on rat locomotor activity and pharmacokinetics, administered alone or in combination by the intragastric route. The pharmacokinetic parameters were determined using non-compartmental analysis and the relationships between the locomotor activity and drug concentrations using sigmoidal Emax modeling. Results: Locomotor activity significantly increased during the first hour post-administration with the MDPV/4-MMC combination in comparison to MDPV (p max (16.4 ± 5.5 versus 62.2 ± 14.2?μg/L, p 0 → ∞ (708 ± 91 versus 3316 ± 682?μg/L/min, p max model fitted the observed data well; MDPV being markedly more potent than 4-MMC (EC50, 0.043 versus 0.7?μmol/L). The enhancing factor representing the MDPV contribution to the alteration in the relationships between locomotor activity and 4-MMC concentrations was 0.3. Conclusion: An MDPV/4-MMC combination results in enhanced stimulant effects in the rat, despite significant reduction in MDPV bioavailability. Enhanced effects could be explained by increased MDPV distribution and/or possible complementation at the brain dopaminergic targets. However, the exact consequences of the MDPV/4-MMC combination in humans remain to be clarified.

Illicit rac-MDPV (3,4-methylenedioxypyrovalerone), manufactured in clandestine labs, has become widely abused for its cocaine-like stimulant properties. It has recently been found as one of the toxic materials in the so-called bath salts, producing, among other effects, psychosis and tachycardia in humans when introduced by any of the several routes of administration (e.g., intravenous, oral, etc.). The considerable toxicity of this designer drug probably resides in one of the enantiomers of the racemate. In order to obtain a sufficient amount of the enantiomers of rac-MDPV to determine their activity, we improved the known synthesis of rac-MDPV and found chemical resolving agents, (+)- and (-)-2'-bromotetranilic acid, that gave the MDPV enantiomers in >96% enantiomeric excess as determined by 1H nuclear magnetic resonance and chiral high-performance liquid chromatography. The absolute stereochemistry of these enantiomers was determined by single-crystal X-ray diffraction studies. Chirality 27:287-293, 2015. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.