What are the side effects of Losartan (angiotensin II receptor antagonist)?

Side Effects of Losartan

Losartan has a favorable side effect profile compared to ACE inhibitors, with most common side effects including dizziness, upper respiratory infections, nasal congestion, and back pain. 1

Common Side Effects

• Dizziness (3% vs 2% with placebo) 1
• Upper respiratory infections (8% vs 7% 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 changing positions 1
• Syncope (fainting) in some cases 1
• Palpitations 1
• Atrial fibrillation (less common) 1

Renal Side Effects

• Potential worsening of kidney function, particularly in patients with:
  • Pre-existing kidney disease 1
  • Bilateral renal artery stenosis 3
  • Solitary kidney with renal artery stenosis 4
  • Severe heart failure 3
• Hyperkalemia (high blood potassium levels) 1

Metabolic Side Effects

• Unlike beta-blockers, losartan does not cause adverse metabolic effects such as:
  • Decreased HDL cholesterol 5
  • Increased triglycerides 5
  • New-onset diabetes 5

Pregnancy-Related Side Effects

• Pregnancy Category D: Can cause fetal injury and death when used during the second and third trimesters 1
• Potential effects on the fetus include:
  • Oligohydramnios (reduced amniotic fluid) 1
  • Fetal lung hypoplasia 1
  • Skeletal deformations 1
  • Skull hypoplasia 1
  • Anuria 1
  • Hypotension 1
  • Renal failure 1

Musculoskeletal Side Effects

• Myalgia (muscle pain) 1
• Arthralgia (joint pain) 1
• Unlike some antihypertensives, myopathy is not a known adverse effect of losartan 6

Gastrointestinal Side Effects

• Abdominal pain 1
• Constipation 1
• Nausea 1
• Vomiting 1
• Diarrhea (particularly common in patients with type 2 diabetes and diabetic kidney disease) 1

Dermatologic Side Effects

• Urticaria (hives) 1
• Pruritus (itching) 1
• Rash 1
• Photosensitivity 1

Neurological Side Effects

• Somnolence (drowsiness) 1
• Paresthesia (tingling sensations) 1
• Migraine 1
• Sleep disorders 1

Advantages Over ACE Inhibitors

• Significantly lower incidence of cough compared to ACE inhibitors (losartan 17-29% vs. lisinopril 62-69% in patients with history of ACE inhibitor-induced cough) 1
• Less angioedema risk compared to ACE inhibitors 7

Special Considerations

• Monitoring recommendations:

  • Regular monitoring of blood pressure 6
  • Monitoring of kidney function 5, 6
  • Monitoring of serum potassium levels 6
  • No specific monitoring for muscle enzymes required 6

• Contraindications:

  • Pregnancy (especially second and third trimesters) 1
  • Patients taking aliskiren who have diabetes 1
  • Hypersensitivity to losartan or any component of the formulation 1

Potential Pitfalls and Caveats

• Losartan should be used with extreme caution in patients with renovascular disease, as it can cause acute renal failure 4
• Patients with bilateral renal artery stenosis or unilateral stenosis in a solitary kidney are at particularly high risk for renal dysfunction 3
• Losartan may mask symptoms of hypoglycemia in diabetic patients 5
• When normalizing thyroid function in patients with hyperthyroidism, blood pressure monitoring is essential as losartan dosage may need adjustment 8
• The medication should be discontinued if allergic reactions occur (swelling of face, lips, throat, or tongue) 1

Losartan is generally well-tolerated with an overall incidence of adverse events similar to placebo, and discontinuation rates due to adverse events are actually lower with losartan (2.3%) than with placebo (3.7%) 2.