Calcium Channel Blockers in the Treatment of Migraine
Calcium channel blockers have assumed a significant role in the prevention of migraine and cluster headaches.
MECHANISM OF ACTION
The beneficial effects of these agents are attributed to their ability to inhibit the movement of calcium ions across the cell membranes. This prevents mechanical contraction of the muscle wall of the artery. There are several chemically distinct classes of compounds which share the ability to block the influx of calcium into various tissues. These compounds include nifedipine (Procardia), verapamil (Calan), and diltiazem (Cardizem). All of these medicines have a common effect on blood vessels and serve to prevent the arterial constriction associated with migraine side effects.
As the calcium channel blockers possess different chemical structures, one would expect a side effect profile for each subclass to vary. Hypotension (low blood pressure) may be experienced with any of these agents. Especially at the initiation of treatment or when doses are increased, patients should be monitored closely for side effects related to postural hypotension (the tendency for the blood pressure to fall too low when the person assumes the upright position). Patients should be advised that symptoms related to hypotension may occur, and if the symptoms are present, this should be reported to the physician.
Particular care should be exercised if patients are concurrently taking other anti-hypertensive drugs, including beta blockers. Again, calcium channel blockers should be used with caution in patients with congestive heart failure because of their tendency to "slow down" the heart muscle.
Constipation has been reported with most of these agents, but it occurs most often with verapamil (Calan). Edema or swelling can occur with any of these agents, but seems to be more common with nifedipine (Procardia). Other adverse effects associated with calcium channel blockers include flushing, lightheadedness, rash, and nausea. Some of these medicines are potent dilators of blood vessels and may actually create headache as a side effect.
Abrupt withdrawal of calcium channel blockers may cause chest pain, rebound angina, or exacerbation of symptoms. As with the beta blockers, doses should be tapered gradually under medical supervision for at least one to two weeks.
Calcium channel blockers have been demonstrated to be effective in the prophylactic treatment of migraine. Verapamil (Calan) and nimodipine (Nimotop) are more useful than other calcium channel blockers in the treatment of cluster headache. The calcium channel blockers offer an effective alternative to those who cannot tolerate or have been refractory to beta blocking drugs.
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