With parenteral use of furosemide in high doses reversible deafness and tinnitus have been reported when the infusion is faster than 4 mg per minute. Permanent deafness may develop in patients with impaired renal function.
Various forms of skin reactions including rashes, urticarial, exfoliative dermatitis, paraesthesia, pruritis, purpura, photosensitivity and erythema may occur.
Nausea, vomiting, diarrhoea, blurred vision, dizziness, headache, pancreatitis, muscle spasm, cramps, hypotension and allergic reactions may occur.
Furosemide should be used with care in patients with prostatic hypertrophy or impairment of micturition.
Anaemia, leucopenia, agranulocytosis, aplastic anaemia and thrombocytopenia (with purpuric) may occur.
Asymptomatic hyperuricaemia may occur and gout may by precipitated.
Alteration in glucose tolerance tests with abnormalities of the fasting and 2-hours postprandial sugar levels have been observed, and cases of precipitation of diabetes mellitus have been reported.
Furosemide increases urinary excretion of calcium, may lower serum calcium levels and cases of tetany have been reported.
Excessive diuresis may result in dehydration and reduction in blood volume, with circulatory collapse and with the possibility of vascular thrombosis and embolism, particularly in elderly patients. Excessive loss of potassium in patients receiving cardiac glycosides may precipitate digitals toxicity. Care should also be taken in patients receiving potassium-depleting steroid.
Hypokalaemia may be counteracted with a potassium-rich diet. If a deficiency state exists-especially in cirrhosis-the serum potassium must first be restored by potassium rich diet. If a deficiency state exists-especially in cirrhosis-the serum potassium must first be restored by potassium supplementation, and if necessary, sodium and chloride. Because of the strong natriuretic effect of furosemide injection, the sodium levels could be reduced especially if the oedema is reduced quickly. Magnesium depletion may develop. Electrolyte depletion may present as weakness, dizziness, lethargy, cramps in the legs, loss of appetite, vomiting and/or metal confusion.
The safety of furosemide in pregnancy has not been established.
Nephrotoxicity associated with the use of cephalosporins and aminoglycosides may be potentiated when furosemide is used in conjunction with cephalosporins and aminoglycosides. These medicines should not be used together.
Liver damage or dysfunction as well as reversible renal failure have been reported. Furosemide should be used with caution in patients with impaired hepatic or malfunction, or with diabetes mellitus or adrenal disease.
Furosemide may enhance the neuromuscular blocking action of non-depolarizing muscle relaxants, such as tubocurarine, as well as effects of guanethidine, methyldopa and rauwolfia alkaloids.
Postural hypotension associated with furosemide may be enhanced by concomitant ingestion of alcohol, barbiturates or narcotics.