Losartan: Cimetidine, phenobarb, rifampicin, fluconazole. Amlodipine: Diltiazem, erythromycin, ketoconazole, itraconazole, ritonavir. Hydrochlorothiazide: Insulin, oral diabetes medication, other BP medicine, alcohol; barbiturates (eg, amobarbital, butabarbital, phenobarb, primidone, pentobarbital, thiopental); narcotics eg, codeine, morphine, oxycodone & hydrocodone; cholestyramine, colestipol; corticosteroids eg, prednisone, hydrocortisone, dexamethasone; norepinephrine, corticotropin; muscle relaxants eg, tubocurarine; lithium; NSAIDs.