Researchers are warning that a drug increasingly being used to prevent cluster headaches can cause heart problems.
They say those people who take the drug verapamil for cluster headaches need to be closely monitored with electrocardiograms (EKGs) for potential development of irregular heartbeats.
The researchers from the National Hospital for Neurology and Neurosurgery in London, say the benefit of taking verapamil to alleviate the devastating pain of cluster headaches has to be balanced against the risk of causing a heart abnormality that could progress into a more serious problem.
Cluster headaches are a rare but severe form of headache that manifests as bouts of very severe pain, one or many times per day, for months at a time, usually followed by a period of remission.
Verapamil, a calcium-channel antagonist drug, is approved by the U.S. Food and Drug Administration for the treatment of cardiac arrhythmias and high blood pressure.
The medicine is typically given in doses of 180 to 240 milligrams per day to help ease hypertension.
Dr. Peter Goadsby, of professor of neurology at University College London carried out a review of the medical records of 217 patients with an average age of 44 who given verapamil to treat their cluster headaches, and found that 128 had undergone an EKG, 108 of which were available in the medical records.
At the outset the participants started taking the verapamil and were then given an EKG and an increase in the dosage of the drug every two weeks until the headaches were stopped or they started having side effects.
A total of 21 patients, or 19 percent, had problems with the electrical activity of the heart, or irregular heartbeats, while taking the drug and although most cases were not considered serious, one person needed a permanent pacemaker due to the problem.
One in three (34 percent) developed non-cardiac side effects such as lethargy and constipation.
A total of 37 percent of the participants had slower than normal heart rates while on the drug, but the condition was severe enough to warrant stopping the use of the drug in only four cases.
Goadsby says those taking verapamil for cluster headaches should have regular EKGs but for the most part when a cardiac problem does arise, it will typically go away once the treatment is halted.
Cluster headache affects about 69 in every 100,000 people and men are six times more likely than women to be afflicted; the typical age of onset is around 30.
The study is published in the current issue of Neurology, the medical journal of the American Academy of Neurology.