Adverse biochemical and clinical consequences of furosemide administration.

Nurse monitors collected clinical and laboratory data from 204 hospitalized patients receiving furosemide (122 men and 82 women; mean age 69.6 years). Biochemical abnormalities and clinical problems definitely or probably induced by any drug occurred in 70.6% and 49.0% respectively of the patients, and were attributed to furosemide in 81.3% and 13.0% respectively of these patients. The most important clinical events were dehydration and hypotension. Furosemide-induced hypochloremia, hypokalemia and hyponatremia occurred in 35.8%, 25.0% and 24.5% of the patients respectively. Most of the biochemical changes were slight, and only 3.9% of the patients had a furosemide-induced decrease in the serum potassium concentration to less than 3.0 mmol/L. Surprisingly, 24.5% of the patients also manifested drug-induced hyperkalemia. Administration potassium supplements or spironolactone, or both, concurrently with furosemide was responsible in most cases for the development of hyperkalemia. The occurrence of drug-induced adverse effects after 2 weeks of hospitalization was significantly associated (P less than 0.05) with subsequent prolongation of hospitalization. The high frequency of drug-induced events warrants careful monitoring of all patients receiving furosemide in spite of the low frequency of serious toxic effects produced by the drug.