What are the contraindications for Losartan (angiotensin II receptor antagonist)?

Contraindications for Losartan

Losartan is contraindicated in patients who are hypersensitive to any component of the product, for coadministration with aliskiren in patients with diabetes, during pregnancy, and in patients with bilateral renal artery stenosis. 1, 2

Absolute Contraindications

1. Hypersensitivity reactions:

   • Patients with known allergies to losartan or any component of the formulation 1
   • History of angioedema with previous ARB use 2

2. Pregnancy:

   • Contraindicated in all trimesters of pregnancy 2, 3
   • Can cause fetal toxicity, especially when used in second and third trimesters 3
   • Associated with neonatal acute kidney injury, lung toxicity, skull hypoplasia, and congenital malformations 2

3. Drug interactions:

   • Coadministration with aliskiren in patients with diabetes 1
   • This combination increases risk of hyperkalemia, hypotension, and kidney impairment 2

4. Bilateral renal artery stenosis:

   • Contraindicated due to risk of acute kidney injury 2, 4
   • ARBs cause efferent arteriolar vasodilation, which can severely reduce glomerular filtration pressure in these patients 4

Relative Contraindications/Cautions

1. Renal impairment:

   • Use with caution in patients with severe renal dysfunction 3
   • Monitor renal function and potassium levels closely 5

2. Hepatic dysfunction:

   • Use with caution in patients with liver disease 5
   • Though no dosage adjustment is needed in mild hepatic impairment 3

3. Hyperkalemia risk:

   • Caution when used with potassium-sparing diuretics (spironolactone, triamterene) 5
   • Monitor potassium levels regularly 2

4. Breastfeeding:

   • Should not be administered to breast-feeding mothers 5
   • May be harmful to newborns

5. Hypotension risk:

   • Caution in volume-depleted patients 2
   • Monitor blood pressure closely when initiating therapy

Special Populations

1. Pediatric patients:

   • Limited data on safety and efficacy in children 2
   • When used in pediatrics, dosing is weight-based 2

2. Elderly patients:

   • No significant age-related changes in pharmacokinetics 3
   • No specific dosage adjustment needed based on age alone

Clinical Considerations

• When switching from ACE inhibitors to losartan due to side effects like cough, allow a washout period of at least 24 hours 2

• For patients with heart failure who might benefit from ARB therapy but have contraindications, consider hydralazine/nitrate combinations as alternatives 4

• Unlike ACE inhibitors, losartan may have a beneficial effect on uric acid levels, which could be advantageous in patients with hyperuricemia 6

• The maximum recommended daily dose is 100 mg, which can be administered once daily or divided into two doses 3

Remember that while losartan has a generally favorable safety profile compared to some other antihypertensives, these contraindications should be strictly observed to prevent serious adverse outcomes, particularly in high-risk populations such as pregnant women and those with significant renal impairment.