Which is more likely to cause a cough, capturing or verapamil (calcium channel blocker)?

Captopril is More Likely to Cause Cough Than Verapamil

Captopril, an ACE inhibitor, is significantly more likely to cause cough than verapamil (a calcium channel blocker). While verapamil may occasionally cause respiratory symptoms in certain populations, ACE inhibitor-induced cough is a well-established and common side effect.

ACE Inhibitor-Induced Cough (Captopril)

ACE inhibitor-induced cough is characterized by:

• Dry, non-productive cough with throat tickling/irritation
• Not dose-dependent
• Higher incidence in women, non-smokers, and people of Chinese origin 1
• Occurs in approximately 5-35% of patients taking ACE inhibitors

Mechanism

• Accumulation of bradykinin and substance P in the upper respiratory tract due to reduced degradation by ACE
• Stimulation of prostaglandin production by bradykinin
• Sensitization of sensory nerves in the respiratory tract 1

Timing and Diagnosis

• Can develop at any time during treatment (days to months after initiation)
• Diagnosis confirmed by cough resolution after discontinuation (usually within 1-4 weeks, but may take up to 3 months) 1

Verapamil and Respiratory Effects

Verapamil rarely causes cough as a primary side effect. The most common side effects include:

• Constipation (most common side effect) 2
• Flushing, headache, and edema 3
• Negative inotropic effects 2, 3

Special Considerations with Verapamil

1. Asthmatic patients: Verapamil can potentially cause bronchospasm in patients with asthma, though this is relatively uncommon:

   • Case reports describe acute asthma attacks following sustained-release verapamil administration in patients with pre-existing asthma 4
   • Higher doses (>10mg) of inhaled verapamil have been associated with bronchoconstriction in asthmatic patients 5

2. Comparative safety: In a study comparing captopril and verapamil in hypertensive patients with asthma, no significant cough symptoms were reported with captopril, and neither drug significantly affected respiratory function measurements 6

Clinical Decision Algorithm

When choosing between captopril and verapamil for a patient who is concerned about cough:

1. For patients with no history of asthma or reactive airway disease:

   • Verapamil is preferred over captopril to avoid ACE inhibitor-induced cough

2. For patients with asthma or reactive airway disease:

   • Exercise caution with both medications
   • Consider alternative agents (e.g., ARBs instead of ACE inhibitors)
   • If verapamil is necessary, start with lower doses and monitor closely

3. For patients already experiencing cough:

   • If on an ACE inhibitor like captopril, consider switching to verapamil or an ARB
   • Resolution of cough within 1-4 weeks after discontinuation confirms ACE inhibitor as the cause 1

Important Clinical Considerations

• ACE inhibitor-induced cough is often misattributed to other causes, leading to unnecessary testing and treatment 1
• Verapamil should be used with caution in patients with impaired left ventricular function due to its negative inotropic effects 2, 3
• Verapamil is contraindicated if β-blockers have been taken by the patient because of the risk of profound bradycardia and hypotension 2
• When evaluating cough in patients on either medication, consider other common causes like respiratory infections, asthma, GERD, or post-nasal drip 1