Symptomatic hyponatraemia when combined with carbamazepine. Predisposes to allopurinol sensitivity reactions and impaired renal function. Potentiates hypotensive effect of beta blockers and ACE inhibitors; these also reduce diuretic-induced hypokalaemia. Potentially Fatal: Enhance neuromuscular blocking action of competitive muscle relaxants. Cross-allergy with sulphonamides and sulphonylurea hypoglycaemics with resultant acute interstitial nephritis and vasculitis. Potentiates bone-marrow suppression caused by anticancer drugs. Potentiates aminoglycoside nephrotoxicity. Impaired control of diabetes by oral hypoglycaemic agents. May precipitate digitalis toxicity and lithium toxicity. Increased risk of hypokalaemia with corticosteroids. Prolongs paralysis caused by tubocurarine.