Klacid: Potential severe drug interaction effects w/ cisapride, domperidone, pimozide, astemizole, terfenadine, ergot alkaloid, oral midazolam, HMG-CoA reductase inhibitors. Concomitant use w/ efavirenz, nevirapine, rifampicin, rifabutin, rifapentine, etravinine, fluconazole, ritonavir; antiarrhythmics, oral hypoglycemic agents/insulin, CYP3A-based interactions, omeprazole, sildenafil, tadalafil, vardenafil, theophylline, carbamazepine, tolterodine, triazolobenzodiazepines eg, alprazolam, midazolam, triazolam; colchicine, digoxin, zidovudine, phenytoin, valproate; atazanavir, Ca-channel blockers, itraconazole, saquinavir. Controloc: Reduced absorption w/ pH-dependent drugs eg, ketoconazole. Ospamox: May promote skin rashes w/ allopurinol. Not to be combined w/ bacteriostatic antibiotics eg, tetracyclines, chloramphenicol. Reduced tissue distribution & diffusion by probenecid. Reduced efficacy of OCs. Reduced absorption by antacid. False +ve non-enzymatic urinary glucose test result. Impaired urobilinogen tests.