Fengabine (SL-79,229) is a drug which was investigated as an antidepressant but was never marketed. Its mechanism of action is unknown, but its antidepressant effects are reversed by GABA<sub>A</sub> receptor antagonists like bicuculline and it has hence been labeled as GABAergic; however, it does not actually bind to GABA receptors, nor does it inhibit GABA-T. In clinical trials, fengabine's efficacy was comparable to that of the tricyclic antidepressants, but with a more rapid onset of action and much less side effects. Notably, fengabine lacks any sedative effects.