Lasix (Furosemide)

Lasix is a loop diuretic used to manage fluid overload and high blood pressure.

• Edema associated with heart failure: reduces fluid accumulation by increasing urinary output.
• Edema associated with liver cirrhosis: helps remove excess ascitic fluid.
• Edema associated with renal disease: facilitates removal of retained sodium and water.
• Hypertension: lowers blood pressure by decreasing plasma volume.

• Furosemide inhibits the Na⁺/K⁺/2Cl⁻ cotransporter in the thick ascending limb of the loop of Henle, blocking reabsorption of sodium, chloride, and potassium. This disruption creates an osmotic gradient that drives water into the tubular lumen, resulting in increased urine volume and reduced extracellular fluid volume, thereby lowering blood pressure and alleviating edema.

Furosemide may cause a range of adverse reactions, from mild to severe.

Common Side Effects

• Increased urination: frequent need to void.
• Electrolyte imbalance: low potassium, sodium, or magnesium levels.
• Dehydration: feeling of thirst or dry mouth.
• Hypotension: dizziness or light‑headedness upon standing.
• Headache: mild to moderate intensity.
• Muscle cramps: especially in the calves.

Serious or Rare Side Effects

• Ototoxicity: hearing loss or ringing in the ears, especially with high doses.
• Severe allergic reaction: rash, itching, swelling, or difficulty breathing.
• Acute renal failure: sudden decline in kidney function.
• Thrombocytopenia: low platelet count leading to easy bruising.
• Severe hyponatremia: dangerously low blood sodium.
• Pancreatitis: abdominal pain and elevated enzymes.

Before initiating therapy, several safety considerations are recommended.

• Monitor electrolytes: check potassium, sodium, and magnesium regularly.
• Assess renal function: evaluate creatinine and eGFR before and during treatment.
• Adjust dose in hepatic impairment: use lower starting doses in patients with liver disease.
• Use caution in hypotension: avoid rapid positional changes to reduce fall risk.
• Avoid abrupt discontinuation: taper dose to prevent rebound fluid retention.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

Furosemide can interact with several medications, requiring careful management.

Major Interactions (Avoid)

• Aminoglycoside antibiotics: increased risk of ototoxicity.
• NSAIDs: may blunt diuretic effect and worsen renal function.
• Lithium: can raise lithium levels leading to toxicity.
• Cyclosporine: heightened nephrotoxic potential.
• Antihypertensive agents: may cause excessive blood pressure drop.

Moderate Interactions (Monitor Closely)

• ACE inhibitors or ARBs: monitor potassium and renal function.
• Other diuretics: risk of additive electrolyte disturbances.
• Corticosteroids: may enhance fluid loss and electrolyte shifts.
• Digoxin: monitor serum levels due to altered renal clearance.