Increased conc w/ medicines causing kidney problems; tetracyclines, metronidazole, co-trimoxazole, trimethoprim & spectinomycin; NSAIDs (eg, diclofenac or ibuprofen) including COX-II inhibitors eg, celecoxib; ACE inhibitors (eg, ramipril or lisinopril) or angiotensin II receptor antagonists (eg, losartan or irbesartan); diuretics including herbal prep; steroids eg, prednisolone, betamethasone or hydrocortisone. Decreased conc w/ theophylline or caffeine; Na bicarbonate; carbonic anhydrase inhibitors; urea. Risk of causing other side effects w/ haloperidol, olanzapine or clozapine; carbamazepine, phenytoin or clonazepam; methyldopa; SSRIs (eg, fluoxetine or paroxetine), tricyclics (eg, amitriptyline), tetracyclics; Ca channel blockers (eg, amlodipine or diltiazem); muscle relaxants; NSAIDs eg, indomethacin; triptans eg, sumatriptan. Risk of serious heart rhythm disorders w/ quinidine, procainamide, disopyramide, amiodarone, ajmaline, cibenzoline, hydroquinidine, azimilide, dofetilide, ibutilide, sotalol; ranolazine; arsenic trioxide; erythromycin (IV), sparfloxacin; amisulpride, haloperidol, pimozide, sertindole, mesoridazine, clozaril, droperidol, thioridazine; terfenadine, astemizole; cisapride; mefloquine, artemisinin derivatives, halofantrine; ketanserin; dolasetron.