Reduced excretion of lithium. Risk of arrhythmias w/ drugs that prolong QT interval or produce hypokalaemia eg, class I & class III antiarrhythmics (eg, quinidine, hydroquinidine, disopyramide, amiodarone, sotalol, ibutilide, dofetilide); cardiac glycosides (digoxin); antipsychotics (eg, sultopride, phenothiazines, benzamide, butyrophenones); other neuroleptics (pimozide); other miscellaneous substances (eg, bepridil, cisapride, erythromycin, halofantrine, sparfloxacine, pentamidine, quinolone). Increased K loss w/ amphotericin B, glucocorticoids, carbenoxolone, tetracosactide, laxatives, liquorice. Increased risk of hyponatraemia w/ carbamazepine or aminoglutethimide. Risk of induced acute renal failure in cases of pre-existing hypovolaemia & reduced diuretic, natriuretic & antihypertensive effect of furosemide w/ NSAIDs. When co-administered w/ high doses of salicylates, predisposition for salicylic toxicity may be increased. Potentiated hypotensive effects &/or renal effects of ACE inhibitors & AIIA. Potentiated effect of other antihypertensives (eg, other diuretics, β-blocker). Potential for additive hypotensive effect w/ amifostine, baclofen or α-blocker. Increased risk of postural hypotension w/ TCAs (eg, imipramine, nortriptyline, amitriptyline) or antipsychotic agents. May attenuate effects of antidiabetic agents. IV administration of furosemide in a 24-hr period prior to chloral hydrate administration may lead to flush, hyperhidrosis, anxiety, nausea, increase in BP & tachycardia. Blood levels of furosemide & of fibric acid derivates (eg, clofibrate & fenofibrate) may be increased during concurrent administration. Concomitant administration of furosemide & iodinated contrast media may increase the risk of contrast media associated acute renal failure. Increased blood levels of metformin. Reduced bioavailability w/ colestyramine & colestipol. May intensify nephrotoxic effects of nephrotoxic drugs (eg, cephaloridine, cephalothin, ceftazidime, polymyxins, aminoglycosides, organoplatins, immunosuppressants, foscarnet, pentamidine). Risk of renal impairment w/ cephalosporins. Risk of ototoxicity w/ cisplatin. May intensify ototoxicity of aminoglycosides (eg, kanamycin, gentamicin, tobramycin). In small doses of furosemide, potentiated neuromuscular blockade of competitive neuromuscular blocker (curare-type muscle relaxants like atracurium & tubocurarine) & depolarising neuromuscular blocker (like succinylcholine); in high doses, antagonism of neuromuscular blockade. Synergistic effect w/ K-sparing diuretics. Decreased clearance of theophylline. Increased risk of dehydration, hyponatraemia & hypokalaemia w/ thiazides. Reduced effect w/ probenecid, methotrexate, other drugs that undergo significant renal tubular secretion. Attenuated effect w/ anticonvulsants (eg, phenytoin, phenobarb). Attenuated effect of pressor amines. Increased risk of gouty arthritis & higher serum creatinine value w/ ciclosporin.