- The concurrent use of benzodiazepines, barbiturates, neuroleptics, phenytoin tricyclic antidepressants, gabapentinoids, tramadol, clonidine, cimetidine, rifampicin, protease inhibitors, St John's wort (Hypericum perforatum), macrolides and antimycotics such as ketoconazole and fluconazole is not allowed.