- Patient receiving treatment with amantadine, ketamine, dextrometorphan, L-Dopa, dopaminergic, anticholinergic agonists, barbiturate, neuroleptic, IMAO, antispastic agents, dantrolen or baclofen, phenitoin, cimetidine, ranitidine, procainamide, quinidine, quinine, nicotine, hydrochlorothiazide, warfarine