Duloxetine Inhibits Effects of MDMA (‘‘Ecstasy’’) In Vitro and in Humans in a Randomized Placebo-Controlled Laboratory Study Ce ´ dric M. Hysek 1. , Linda D. Simmler 1. , Valentina G. Nicola 1 , Nerina Vischer 1 , Massimiliano Donzelli 1 , Stephan Kra ¨ henbu ¨ hl 1 , Eric Grouzmann 2 , Jo ¨ rg Huwyler 3 , Marius C. Hoener 4 , Matthias E. Liechti 1 * 1 Psychopharmacology Research Group, Division of Clinical Pharmacology and Toxicology, Department of Biomedicine and Department of Internal Medicine, University Hospital and University of Basel, Basel, Switzerland, 2 Divisions of Clinical Pharmacology and Toxicology, University Hospital, Lausanne, Switzerland, 3 Department of Pharmaceutical Sciences, University of Basel, Basel, Switzerland, 4 Pharmaceuticals Division, Neuroscience Research, F. Hoffmann-La Roche Ltd., Basel, Switzerland Abstract This study assessed the effects of the serotonin (5-HT) and norepinephrine (NE) transporter inhibitor duloxetine on the effects of 3,4–methylenedioxy-methamphetamine (MDMA, ecstasy) in vitro and in 16 healthy subjects. The clinical study used a double-blind, randomized, placebo-controlled, four-session, crossover design. In vitro, duloxetine blocked the release of both 5-HT and NE by MDMA or by its metabolite 3,4-methylenedioxyamphetamine from transmitter-loaded human cells expressing the 5-HT or NE transporter. In humans, duloxetine inhibited the effects of MDMA including elevations in circulating NE, increases in blood pressure and heart rate, and the subjective drug effects. Duloxetine inhibited the pharmacodynamic response to MDMA despite an increase in duloxetine-associated elevations in plasma MDMA levels. The findings confirm the important role of MDMA-induced 5-HT and NE release in the psychotropic effects of MDMA. Duloxetine may be useful in the treatment of psychostimulant dependence. Trial Registration: Clinicaltrials.gov NCT00990067 Citation: Hysek CM, Simmler LD, Nicola VG, Vischer N, Donzelli M, et al. (2012) Duloxetine Inhibits Effects of MDMA (‘‘Ecstasy’’) In Vitro and in Humans in a Randomized Placebo-Controlled Laboratory Study. PLoS ONE 7(5): e36476. doi:10.1371/journal.pone.0036476 Editor: Jerson Laks, Federal University of Rio de Janeiro, Brazil Received January 2, 2012; Accepted March 31, 2012; Published May 4, 2012 Copyright: ß 2012 Hysek et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by the Swiss National Science Foundation (grant no. 32320_126231) and the University of Basel (grant no. DPH2037). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: One of the authors (MCH) is employed by a commercial company (Hoffmann-La Roche Ltd.). This does not alter the authors’ adherence to all the PLoS ONE policies on sharing data and materials. * E-mail: mliechti@uhbs.ch . These authors contributed equally to this work. Introduction Amphetamine derivatives, including 3,4-methylenedioxy- methamphetamine (MDMA, ‘‘ecstasy’’) bind to monoamine transporters and potently release serotonin (5-hydroxytryptamine [5-HT]), norepinephrine (NE), and dopamine (DA) through the 5- HT (SERT), NE (NET), and DA (DAT) transporters, respectively [1,2,3,4]. The pharmacological effect of MDMA can be blocked by monoamine transporter inhibitors. In vitro, the MDMA-induced release of NE, DA, or 5-HT from rat brain synaptosomes preloaded with monoamines is competitively inhibited by the monoamine transporter inhibitor indatraline [5,6]. In humans, SERT inhibition reduced the psychotropic response to MDMA [7,8,9]. NET inhibition also attenuated the acute effects of MDMA [10] and amphetamine [11] in humans. In contrast, clonidine, which inhibits the vesicular release of NE, did not inhibit the effects of MDMA in humans [12]. Thus, the available evidence indicates that the MDMA-induced transporter-mediated release of 5-HT and NE appears to be involved in aspects of the acute subjective and cardiovascular responses to psychostimulants [2,7,10,11]. However, the response to MDMA in humans was only moderately affected when either the SERT or NET was pharmacologically blocked [7,10]. Therefore, we evaluated the effects of dual SERT and NET inhibition with duloxetine on the pharmacokinetics (PK) and pharmacodynamics (PD) of MDMA in humans. Duloxetine was used because it is the most potent and selective dual SERT and NET inhibitor, although it also inhibits the DAT with 10- to 100-fold lower potency compared with the SERT and NET [13,14]. MDMA is mainly metabolized to 3,4- dihydroxymethamphetamine (HHMA) by cytochrome P450 (CYP) 2D6-mediated O-demethylation, followed by catechol-O- methyltransferase-catalyzed methylation to 4-hydroxy-3-methox- ymethamphetamine (HMMA) [15]. Because duloxetine inhibits CYP 2D6 [16], we expected an increase in plasma MDMA concentrations after duloxetine pretreatment. MDMA is also N- demethylated to the active metabolite 3,4-mehthylenedioxyam- phetamine (MDA). Whether the effects of MDA on 5-HT and NE release are inhibited by transporter inhibitors is unknown. Additionally, the inhibition of MDMA’s effect on 5-HT and NE release by duloxetine has not been studied. Therefore, we also assessed the effects of duloxetine on 5-HT and NE release induced by MDMA or MDA in vitro using cells that express the respective human transporters. We also sought to link the in vitro and in vivo data to provide additional insights into the differential modulatory PLoS ONE | www.plosone.org 1 May 2012 | Volume 7 | Issue 5 | e36476