Increased effect/toxicity w/ delavirdine, ketoconazole, nicardipine, NSAIDs, sulfonamides, tolbutamide. Increased hypoglycemic effect w/ β-blockers, chloramphenicol, cimetidine, fibric acid derivatives, fluconazole, pegvisomant, salicylates, sulfonamides, TCAs. Increase effect of cyclosporin. May induce disulfiram-like reaction w/ ethanol. Decreased levels/effect w/ carbamazepine, phenobarb, phenytoin, rifampin, rifapentine, secobarbital. Decreased effect w/ corticosteroids, estrogens, OCs, thiazide & other diuretics, phenothiazines, NSAIDs, thyroid products, nicotinic acid, INH, sympathomimetics, urinary alkalinizers & charcoal. May cause hypoglycemia w/ ethanol, chromium, garlic & gymnema.