Losartan Tablets

Mechanism

Losartan selectively blocks angiotensin II type 1 (AT1) receptors, preventing vasoconstriction and aldosterone secretion. This leads to reduced blood pressure, decreased vascular resistance, and renal protection.

Pharmacokinetics

• Absorption: Rapid oral absorption; bioavailability ~33%.
• Distribution: Highly protein bound (~99%).
• Metabolism: Hepatic metabolism via CYP2C9 and CYP3A4 to active metabolite (EXP3174).
• Elimination: Excreted in urine and feces.
• Half-life: Losartan ≈ 2 hours; active metabolite ≈ 6–9 hours.

Side Effects

• Dizziness
• Fatigue
• Hyperkalemia
• Hypotension
• Rare: angioedema, renal impairment

Contraindication

• Hypersensitivity to Losartan or excipients
• Pregnancy (especially 2nd and 3rd trimester)
• Severe hepatic impairment

Interaction

• Potassium-sparing diuretics / supplements: Increased risk of hyperkalemia.
• NSAIDs: May reduce antihypertensive effect and impair renal function.
• Other antihypertensives: Additive hypotensive effect.
• Rifampicin: May reduce plasma levels of Losartan.

Warning and Precautions

• Monitor blood pressure and renal function regularly.
• Check serum potassium levels during therapy.
• Discontinue immediately if pregnancy is detected.
• Use cautiously in patients with renal artery stenosis.