Lasix (Furosemide)

Furosemide (Lasix) acts on the renal loop of Henle to promote diuresis, addressing conditions characterized by fluid retention.

• Edema associated with heart failure: reduces excess fluid accumulation, easing breathlessness and swelling.
• Edema associated with liver cirrhosis: increases urinary output to lower abdominal and peripheral fluid buildup.
• Edema associated with renal disease: facilitates removal of retained fluid when kidney function is compromised.
• Hypertension: lowers blood pressure by decreasing plasma volume through enhanced sodium and water excretion.

• Furosemide inhibits the Na⁺‑K⁺‑2Cl⁻ cotransporter located in the thick ascending limb of the loop of Henle. By blocking this transporter, it prevents reabsorption of sodium, chloride, and potassium, leading to increased urinary excretion of these electrolytes together with water. The resulting diuresis reduces extracellular fluid volume, which helps alleviate edema and lowers systemic blood pressure.

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

Common Side Effects

• Increased urination
• Dizziness or light‑headedness
• Headache
• Electrolyte imbalance (e.g., low potassium)
• Dehydration
• Low blood pressure

Serious or Rare Side Effects

• Severe dehydration
• Significant electrolyte disturbances (hypokalemia, hyponatremia)
• Ototoxicity leading to hearing loss
• Allergic reactions such as rash or angioedema
• Acute renal impairment
• Thrombocytopenia or other blood dyscrasias

When prescribing furosemide, clinicians should observe several safety considerations to minimize risks.

• Monitor electrolytes: check serum potassium, sodium and magnesium regularly.
• Assess renal function: evaluate creatinine clearance before and during therapy.
• Adjust dose in hepatic impairment: use lower doses in patients with liver disease.
• Use caution in hypotension: avoid rapid volume depletion in patients with low blood pressure.
• Avoid use in anuria: furosemide is ineffective when urine output is absent.
• Store at below 25°C: keep in the original packaging, protect from moisture.

Furosemide can interact with other medicines, altering its efficacy or increasing toxicity.

Major Interactions (Avoid)

• NSAIDs: may blunt diuretic response and reduce fluid loss.
• Aminoglycoside antibiotics: increased risk of ototoxicity.
• Lithium: furosemide can raise lithium concentrations, risking toxicity.
• Cyclosporine: combined use may worsen nephrotoxicity.
• ACE inhibitors or ARBs: may cause excessive hypotension and renal impairment.

Moderate Interactions (Monitor Closely)

• Other antihypertensives: additive blood pressure‑lowering effect.
• Antidiabetic agents: diuresis may affect glucose control.
• Corticosteroids: may enhance fluid and electrolyte loss.
• Digoxin: electrolyte shifts can predispose to digoxin toxicity.
• Warfarin: possible increase in anticoagulant effect.