Losartan
Cozaar | Lortaan
Overview
Selectively blocks binding of angiotensin II to AT1 receptors, producing vasodilation, reduced aldosterone secretion, and decreased blood pressure.
Indications
- Hypertension
- Diabetic nephropathy (type 2 diabetes)
- Stroke risk reduction in patients with hypertension and left ventricular hypertrophy
- Heart failure (when ACE inhibitors not tolerated)
Contraindications
- Pregnancy
- Concurrent use with aliskiren in patients with diabetes
- History of angioedema with ARBs
Classification
Mechanism of Action
Selectively blocks binding of angiotensin II to AT1 receptors, producing vasodilation, reduced aldosterone secretion, and decreased blood pressure.
Pharmacodynamics
ARB (angiotensin II receptor blocker). Does not inhibit ACE or accumulate bradykinin (fewer cough side effects than ACE inhibitors).
Pharmacokinetics
- Absorption
- Well absorbed orally. Undergoes significant first-pass metabolism.
- Distribution
- Does not cross blood-brain barrier well.
- Metabolism
- Hepatic via CYP2C9 and CYP3A4 to active metabolite (EXP-3174) which is 10-40x more potent.
- Excretion
- Renal (35%) and fecal (60%).
- Half-life
- 2 hours (losartan); 6-9 hours (active metabolite)
- Bioavailability
- 25-35%
- Protein Binding
- 98.7%
Dosage
Typical dosage: 25-100mg once or twice daily
Available Forms
- Tablet
Side Effects
Common
- Dizziness
- Upper respiratory infection
- Nasal congestion
- Back pain
Serious
- Hyperkalemia
- Acute renal failure
- Angioedema (rare)
Rare
- Hepatitis
- Rhabdomyolysis
- Vasculitis
Drug Interactions
Risk of hyperkalemia. Monitor potassium levels, especially with renal impairment.
ARBs may increase lithium levels. Monitor lithium concentration closely.
Warnings
Drugs that act on the renin-angiotensin system can cause injury and death to the developing fetus. Discontinue as soon as pregnancy is detected.
Pregnancy
Category D
Toxicity
LD50 >1000 mg/kg (oral, rat)
Overdose
Symptoms: hypotension, tachycardia, bradycardia. Treatment: supportive, IV fluids. Not removed by hemodialysis.
References
Looking for patient-friendly information? Visit RemedyDoor for easy-to-read guides about this medication.