Clinical toxicity of furosemide in hospitalized patients. A report from the Boston Collaborative Drug Surveillance Program.

Of 17,068 hospitalized medical patients monitored in a drug surveillance program, 2,367 (13.9 per cent) received furosemide. Of these patients, 53 per cent were hospitalized with a primary (first) diagnosis of cardiovascular disease; many other patients had cardiovascular disorders coincident with other diseases. In 78 per cent of cases the indication for furosemide therapy was congestive heart failure. Adverse reactions were attributed to furosemide in 239 patients (10.1 per cent), but in only 14 instances were the unwanted effects considered life-threatening. The most common adverse reactions were: intravascular volume depletion (4.6 per cent of furosemide recipients), hypokalemia (3.6 per cent), and other eletrolyte disturbances (1.5 per cent). Many patients experienced more than one manifestation of toxicity. The over-all frequency of adverse reactions increased progressively with higher daily doses of furosemide, but was not correlated with total furosemide dose. Among furosemide recipients who also recieved potassium-supplements or potassium-sparing diuretics, hypokalemia was less frequent, less severe, and of slower onset. Coadministration of other diuretics with furosemide was associated with a higher frequency of volume depletion. The findings indicate that furosemide is a relatively safe diuretic in a wide range of clinical situations. Serious adverse reactions are uncommon, and occur primarily in the seriously ill.