Losartan Side Effects: A Comprehensive Overview
The most common side effects of losartan include upper respiratory infections, dizziness, nasal congestion, and back pain, with dizziness being the only adverse effect occurring more frequently than placebo. 1
Common Side Effects
- Upper respiratory infections (8% vs. 7% with placebo) 1
- Dizziness (3% vs. 2% with placebo) 1
- Nasal congestion (2% vs. 1% with placebo) 1
- Back pain (2% vs. 1% with placebo) 1
- Headache 1
- Fatigue/asthenia 2
Cardiovascular Side Effects
- Low blood pressure (hypotension), which may cause faintness or dizziness, particularly when standing up 1
- Syncope (fainting) 1
- Palpitations 1
- Atrial fibrillation (less common) 1
Renal Side Effects
- Worsening of kidney function, particularly in patients with pre-existing kidney problems 1
- Potential for acute renal failure in patients with bilateral renal artery stenosis, severe heart failure, or severe volume depletion 3, 4
- Regular monitoring of kidney function is essential, similar to ACE inhibitors 5
Metabolic and Electrolyte Side Effects
- Hyperkalemia (high blood potassium levels) 1
- Unlike some other antihypertensives, losartan does not cause adverse metabolic effects such as decreased HDL cholesterol or increased triglycerides 6
Gastrointestinal Side Effects
Musculoskeletal Side Effects
- Myalgia (muscle pain) 1
- Arthralgia (joint pain) 1
- Myopathy is not a known adverse effect of losartan 6
Neurological Side Effects
Skin Side Effects
Special Considerations and Contraindications
- Pregnancy: Losartan is contraindicated during pregnancy (Category D), especially in the second and third trimesters, as it can cause fetal injury and death 1
- Breastfeeding: Not recommended during breastfeeding as losartan may pass into breast milk 1, 7
- Renal artery stenosis: Should be used with extreme caution in patients with bilateral renal artery stenosis or stenosis in a solitary kidney due to risk of acute renal failure 3, 4
- Hypersensitivity: Allergic reactions including swelling of face, lips, throat, or tongue require immediate medical attention 1
Advantages Over ACE Inhibitors
- Significantly lower incidence of cough compared to ACE inhibitors 5, 2
- In studies of patients who experienced cough with ACE inhibitors, the incidence of cough with losartan was similar to placebo or hydrochlorothiazide 1
- Better overall tolerability profile with fewer withdrawals due to adverse effects (2.3% with losartan vs. 3.7% with placebo) 2
Drug Interactions
- Potential interactions with:
Monitoring Recommendations
- Regular blood pressure monitoring 6
- Kidney function monitoring is essential, similar to ACE inhibitors 5
- Serum potassium levels should be monitored 1
- No specific monitoring for muscle enzymes is required 6
Important Caveats and Pitfalls
- First-dose hypotension is uncommon compared to ACE inhibitors, possibly due to slower onset of action 8
- Angioedema, though rare, has been reported with losartan as with ACE inhibitors 8
- Patients should be advised to lie down if feeling faint or dizzy and contact their doctor immediately 1
- Losartan should be used with caution in patients with severe heart failure, as it may reduce renal perfusion 3
- Losartan may need dose adjustment when thyroid function normalizes in patients with hyperthyroidism 6
Losartan is generally well-tolerated with a favorable side effect profile compared to other antihypertensive medications, particularly ACE inhibitors, making it a suitable alternative for patients who cannot tolerate ACE inhibitors due to cough or angioedema 5, 2.