Verapamil (Calan, Isoptin) is an effective drug for the prevention of cluster headaches. It is sometimes used for migraines as well. However, the evidence for its efficacy is weak. A double-blind crossover trial by Dr. Glen Solomon and his colleagues in Ohio examined the effect of 320 mg of verapamil on 12 migraine patients. The drug was more effective than the placebo. Other small studies also suggested that it might help some patients.
Verapamil has a reputation among headache specialists as being effective for the prevention of frequent migraine auras and other neurological symptoms that occur with migraines. Unfortunately, there are no controlled trials to support this impression.
The starting dose of verapamil is 120 mg a day with a possible escalation up to 480 mg. For cluster headaches, the starting dose is 240 mg and the maximum dose is as high as 960 mg. Verapamil can cause arrhythmia (irregular heartbeat), especially at higher doses. I recommend an electrocardiogram before every increase of the dose above 240 mg.
The two most common side effects of verapamil are constipation and swelling of the feet. In some of my patients, constipation was severe and resistant to treatment. They had to stop taking the drug.
