Clinical reference · Card 10 of 11 · Safety
Verapamil safety — ECG monitoring
Cluster headache doses far exceed cardiology doses. Conduction abnormalities are common and dose-independent.
19%developed arrhythmias, including heart block
36%developed bradycardia (heart rate <60)
n=369patients in the Harrow audit cohort
Abnormalities occurred at all doses in the audit — a low dose does not remove the need for an ECG.
PRACTICAL PROTOCOL
1Baseline ECG before the first dose.
2Repeat ECG 10 days after each dose increase, before escalating further.
3Escalate in 80 mg increments. EAN advises at least 240 mg/day; higher doses under specialist supervision.
4Once stable, ECG every 6 months while on treatment.
5Stop escalating and seek advice if the PR interval lengthens, or if bradycardia, heart block or hypotension develop.
Before you startContraindicated in second- or third-degree AV block, sick sinus syndrome, significant left ventricular dysfunction and severe hypotension. Avoid with beta-blockers; verapamil inhibits CYP3A4 — check interactions. Constipation is the commonest reason patients stop; modified-release preparations reduce dosing frequency.
NICE 1.3.39: if unfamiliar with verapamil for cluster headache, seek specialist advice before starting, including advice on ECG monitoring.
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