To evaluate the psychopharmacological effects and potential abuse liability of the novel analgesic flupirtine maleate the subjective and behavioral effects of orally administered flupirtine, lorazepam and placebo were studied in polydrug abusers. Effects were measured before and for 6 h after drug administration under double-blind conditions. At therapeutic doses flupirtine was not differentiated from placebo. Lorazepam and higher doses of flupirtine produced increases in subject-rated liking, ARCI MBG scale scores, and sedative-like effects including impaired psychomotor performance. Flupirtine, but not lorazepam, increased ratings on measures indicating dysphoric effects. The results indicate that flupirtine has some sedative-like effects but that its abuse potential is probably modest.