Can bosentan cause dizziness or lightheadedness?

Bosentan and Dizziness: Clinical Evidence and Management

Yes, bosentan can cause dizziness or lightheadedness (giddiness) as a recognized side effect. This symptom is among the commonly reported adverse events in patients taking this endothelin receptor antagonist.

Evidence for Dizziness as a Side Effect

• Dizziness is documented as one of the frequently reported clinical adverse events with endothelin receptor antagonists including bosentan 1
• In clinical trials, dizziness was specifically noted as an adverse reaction associated with bosentan therapy 2
• The mechanism may be related to bosentan's vasodilatory effects, which can moderately reduce blood pressure, potentially leading to symptoms of lightheadedness 3

Pharmacological Basis

• Bosentan is a dual endothelin receptor antagonist (ERA) that blocks both endothelin A and B receptors 1
• By blocking these receptors, bosentan causes vasodilation in the pulmonary vasculature but can also affect systemic circulation 3
• The moderate reduction in blood pressure caused by bosentan may contribute to the experience of dizziness in some patients 3

Frequency and Context

• Dizziness appears to be less common than other side effects such as headache, peripheral edema, and abnormal liver function 2
• The symptom may be more pronounced:
  • During initial dose titration (starting at 62.5 mg twice daily for 4 weeks before increasing to 125 mg twice daily) 4
  • In elderly patients who may have decreased baroreceptor response 5
  • In patients with pre-existing cardiovascular conditions 1

Management Considerations

• Monitor for symptoms of dizziness particularly during the initial titration phase 4
• If dizziness occurs:
  • Evaluate for signs of hypoperfusion (confusion, altered mental status, hypotension) 5
  • Consider checking blood pressure to rule out significant hypotension 5
  • Assess if the symptom is transient or persistent 5

Clinical Implications

• For most patients, dizziness is mild and may resolve with continued treatment 2
• If dizziness is severe or persistent:
  • Dose adjustment may be considered, particularly in elderly patients 5
  • Evaluate for other potential contributing medications 5
  • Ensure adequate hydration 5

Other Important Side Effects to Monitor

• Hepatotoxicity is a more serious concern with bosentan, requiring monthly liver function tests 1
• Anemia may develop and should be monitored with regular hemoglobin/hematocrit checks 1
• Potential teratogenic effects require careful contraception in women of childbearing age 1

Bosentan remains an important treatment option for pulmonary arterial hypertension despite these potential side effects, with evidence showing substantial benefits in exercise capacity, hemodynamics, and functional class 1, 6.