5 WARNINGS AND PRECAUTIONS
5.1 Fluid, Electrolyte, and Metabolic Abnormalities
Furosemide may cause fluid, electrolyte, and metabolic abnormalities such as hypovolemia, hypokalemia, azotemia, hyponatremia, hypochloremic alkalosis, hypomagnesemia, hypocalcemia, hyperglycemia, or hyperuricemia, particularly in patients receiving higher doses, patients with inadequate oral electrolyte intake, and in elderly patients. Excessive diuresis may cause dehydration and blood volume reduction with circulatory collapse and possibly vascular thrombosis and embolism, particularly in elderly patients. Serum electrolytes, CO2, BUN, creatinine, glucose, and uric acid should be monitored frequently during furosemide therapy.
In patients with hepatic cirrhosis and ascites, sudden alterations of fluid and electrolyte balance may precipitate hepatic encephalopathy and coma. Treatment in such patients is best initiated in the hospital with small doses and careful monitoring of the patient's clinical status and electrolyte balance.
5.2 Worsening Renal Function
Furosemide can cause dehydration and azotemia. If increasing azotemia and oliguria occur during treatment of severe progressive renal disease, furosemide should be discontinued [see Clinical Pharmacology (12.3)].
Furosemide use in the first year of life, especially in patients born pre-term, may precipitate nephrocalcinosis/nephrolithiasis. Therefore renal function must be monitored and renal ultrasonography performed in this age group [see Use in Specific Populations (8.4)].
5.3 Ototoxicity
Cases of tinnitus and reversible or irreversible hearing impairment and deafness have been reported. Reports usually indicate that furosemide ototoxicity is associated with rapid injection, severe renal impairment, the use of higher than recommended doses, hypoproteinemia or concomitant therapy with aminoglycoside antibiotics, ethacrynic acid, or other ototoxic drugs. If the physician elects to use high-dose parenteral therapy, controlled intravenous infusion is advisable (for adults, an infusion rate not exceeding 4 mg furosemide per minute has been used) [see Drug Interactions (7.1)].
Hearing loss in neonates, including premature neonates has been associated with the use of Furosemide Injection [see Use in Specific Populations (8.4)].
5.4 Acute Urinary Retention
In patients with severe symptoms of urinary retention (because of bladder emptying disorders, prostatic hyperplasia, urethral narrowing), the administration of furosemide can cause acute urinary retention related to increased production and retention of urine. Thus, these patients require careful monitoring, especially during the initial stages of treatment.