Increased risk of ventricular arrhythmias w/ torsades de pointes-inducing drugs eg, class Ia (quinidine, hydroquinidine, disopyramide) & III (amiodarone, sotalol, dofetilide, ibutilide) antiarrhythmics, antipsychotics eg, phenothiazines (chlorpromazine, cyamemazine, levomepromazine, thioridazine, trifluoperazine), benzamides (amisulpride, sulpiride, sultopride, tiapride), butyrophenones (droperidol, haloperidol); bepridil, cisapride, diphemanil, erythromycin IV, halofantrine, mizolastine, pentamidine, sparfloxacin, moxifloxacin, vincamine IV. Possible reduction in antihypertensive effect w/ NSAIDs (systemic) eg, COX-2 selective inhibitors, high-dose salicylic acid (3 g daily). Risk of sudden hypotension &/or acute renal failure w/ ACE inhibitors. Increased risk of hypokalaemia w/ amphotericin B (IV), gluco- & mineralocorticoids (systemic), tetracosactide, stimulant laxatives. Increased antihypertensive effect w/ baclofen. Hypokalaemia predisposing to the toxic effects of digitalis. May increase incidence of hypersensitivity reactions to allopurinol. Hypokalaemia or hyperkalaemia (particularly in patients w/ renal failure & diabetes) may occur w/ K-sparing diuretics (amiloride, spironolactone, triamterene). Increased risk of metformin-induced lactic acidosis. Increased risk of acute renal failure w/ iodinated contrast media (large doses). Increased antihypertensive effect & risk of orthostatic hypotension w/ imipramine-like antidepressants, neuroleptics. Risk of hypercalcaemia w/ Ca salts. Risk of increased plasma creatinine w/ ciclosporin, tacrolimus. Decreased antihypertensive effect w/ corticosteroids, tetracosactide (systemic). Not recommended: Increased plasma lithium.