Nalmefene (Selincro®) is a selective opioid receptor antagonist, which was licensed in April 2014 in Switzerland for the reduction of alcohol consumption in adults with a high drinking risk level. 200 reports of adverse drug reactions of nalmefene have been documented worldwide in the WHO global pharmacovigilance database between 07.03.1997 to 01.03.2015. In 21 cases (10.5%) nalmefene and an opioid were administered concomitantly, causing withdrawal symptoms. Until now, the regional pharmacovigilance center in Zurich received four cases of nalmefene combined with opioids. This combination should be avoided.