FUROSEMIDE

Loop diuretic suitable when rapid and effective diuresis is required such as cardiac, renal, pulmonary and hepatic oedema. Oral furosemide produces diuresis within 30–60 minutes of administration, and a maximum effect in 1–2 hours. The diuretic action lasts 4–6 hours. Intravenous furosemide produces diuresis within 5 minutes, and a maximum effect in 20–60 minutes; diuresis is complete within 2 hours.

Dosage Forms

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Tablet

40 mg

Injection

10 mg/ml

Uses

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  • Congestive heart failure
  • Pulmonary oedema
  • Ascites
  • Oliguria due to renal failure
  • Oedema due to kidney or liver disorders
  • Adjunct in transfusion (prevention fluid overload)

Dose and Duration

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Oedema
Adult: 20‒50 mg orally, increased in 20 mg steps every 2 hours as necessary. If the effective single dose is more 50 mg, consider using slow IV infusion at a rate not exceeding 4 mg/minute
Child: 0.5‒1.5 mg/kg daily (max. 20 mg daily)
Oliguria (glomerular filtration rate < 20 ml/minute)
Adult: Initially 250 mg over 1 hour by slow IV infusion at a rate not exceeding 4 mg/minute. If urine output is not satisfactory during the hour after the first dose, infuse 500 mg over 2 hours, then infuse 500 mg over 2 hours; if urine output is not satisfactory after second dose, infuse 1 g over 4 hours. If no response, consider dialysis.
Repeat every 24 hours

Contraindications

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  • Hypovolemia or dehydration
  • Obstructed urinary flow e.g. in prostatic hypertrophy
  • Anuria or renal failure with anuria not responding to a furosemide challenge
  • Renal failure by agents that cause renal or liver failure
  • Severe hypokalaemia
  • Severe hyponatraemia
  • Coma due to hepatic encephalopathy
  • Allergy to furosemide
  • Gout

Side Effects

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  • Stomach upset (usually mild)
  • Increased frequency of urination
  • May inhibit breast milk production
  • Dehydration
  • Low blood pressure
  • Electrolyte and water imbalances; low sodium, potassium, magnesium, calcium and chloride levels
  • Hyperuricaemia leading to gout attacks
  • Tinnitus and permanent deafness when infused rapidly
  • Pain at injection site when used intramuscularly
  • Hyperglycaemia

Interactions

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  • Aminoglycosides e.g. amikacin, gentamicin, streptomycin (increased risk of ototoxicity)
  • Vancomycin (increased risk of ototoxicity)
  • Digoxin (increased digoxin toxicity due to hypokalaemia)
  • Enalapril (enhanced hypotensive effect)
  • Lidocaine (reduced effect of lidocaine due to hypokalaemia)
  • Lithium (increased lithium concentration)

Patient Instructions

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  • Report to health worker immediately any signs of increased thirst, headache, hypotension, confusion, muscle cramps, muscle weakness, irregular heart beat and stomach upset

Pregnancy

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  • Do not use

Breast-feeding

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  • Do not use

⚠️ Caution

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  • Use lower doses in elderly as they are more prone to side effects
  • Rapid infusion of intravenous furosemide can cause tinnitus and permanent hearing loss
  • Warning signs of electrolyte disturbances include increased thirst, headache, hypotension, confusion, muscle cramps, muscle weakness, irregular heart beat and stomach upset
  • May be given with a potassium-sparing diuretic to reduce risk of hypokalaemia