Introduction: MDMA (3,4-methylenedioxymethamphetamine), a synthetic ring-substituted amphetamine, has become one of the most widely used recreational psychostimulant drugs in the world. Among recreational ecstasy/MDMA users, polydrug use is a phenomenon whose common purpose is to experience the synergistic effect of the combined drugs, moderate MDMA effects, prevent potential toxicity, enhance a high or come down from a high from other drugs, or simply to treat existing medical conditions. Thus, MDMA-drug interactions (MDMA-DIs) lead to a higher risk of acute and life-threatening MDMA toxicity. Areas covered: This article provides an overview of the MDMA-DIs with pharmaceuticals and drugs of abuse. In addition, available evidence is summarized along with clinical recommendations. Finally, the increasing importance of MDMA-DIs is highlighted. Expert opinion: There is a reduced number of published MDMA-DIs studies and scarce clinically significant MDMA-DIs documented in the literature. Experimental evidence points out the relevance of MDMA-DI's when MDMA is co-administered with pharmaceuticals that are metabolized by the CYP2D6 due to MDMA inhibitory action and in the case of repeated MDMA administration (MDMA-MDMAIs).