Most Common Side Effects of Losartan
The most common side effect of losartan is upper respiratory infection (8% of patients), followed by dizziness (3% of patients), nasal congestion (2%), and back pain (2%) 1.
Common Side Effects Profile
Losartan is generally well-tolerated with an overall incidence of adverse events similar to that of placebo. According to the FDA drug label, the following side effects occur in ≥2% of patients taking losartan and more commonly than with placebo 1:
- Upper respiratory infection (8% vs. 7% with placebo)
- Dizziness (3% vs. 2% with placebo)
- Nasal congestion (2% vs. 1% with placebo)
- Back pain (2% vs. 1% with placebo)
Comparison to ACE Inhibitors
One notable advantage of losartan over ACE inhibitors is its significantly lower incidence of cough:
- Cough occurs in only about 3.1% of patients taking losartan, similar to placebo (2.6%) 2
- Only 17-29% of patients who previously experienced ACE inhibitor-induced cough develop cough on losartan 3
- In controlled studies of patients who had ACE inhibitor cough, the incidence of cough with losartan was 17-29% compared to 62-69% with lisinopril 1
Less Common but Important Side Effects
While not the most common, clinicians should be aware of these potential adverse effects:
- Hypotension, particularly in volume-depleted patients
- Hyperkalemia (high blood potassium)
- Renal function impairment, especially in patients with pre-existing kidney disease
- Angioedema (rare but can occur even in patients who previously experienced angioedema with ACE inhibitors) 3
Monitoring Recommendations
When starting losartan therapy:
- Check renal function and potassium within 1-2 weeks of initiation
- Monitor closely after dose changes, particularly in high-risk patients (systolic BP <80 mmHg, low sodium, diabetes, or impaired renal function) 3
- Be cautious with potassium supplements or salt substitutes containing potassium as they may increase serum potassium 3, 1
Important Contraindications
- Pregnancy (Category D): Losartan should be discontinued immediately if pregnancy is detected as it can cause fetal injury and death when used in the second and third trimesters 3, 1
- Avoid dual RAS blockade with ACE inhibitors or other ARBs as this increases adverse effects without significant clinical benefit 3
Clinical Perspective
The favorable side effect profile of losartan makes it a well-tolerated option for hypertension management. The discontinuation rate due to adverse events with losartan (2.3%) is actually lower than with placebo (3.7%) 1, 2, highlighting its excellent tolerability.
When considering losartan therapy, clinicians should weigh these common side effects against its proven benefits in hypertension management, particularly in patients who have experienced intolerable side effects with ACE inhibitors.