LONDON, Oct. 10 - Four classes of drugs that lower blood pressure also prevent headaches, say researchers here who analyzed data from 94 randomized, placebo controlled trials.
On average the 17,641 patients who were given active treatment lowered systolic blood pressure by 9.4 mm Hg and diastolic pressure by 5.5 mm Hg. Headaches were reduced by a third in all active treatment groups (8%) compared with the 12.4% headache rate among the 6,603 patients randomized to placebo (P<0.001).
Action Points
- Advise patients that four classes of drugs designed to lower blood pressure also may prevent headaches. Those classes are thiazides, beta blockers, ACE inhibitors, and angiotensin II receptor agonists.
- Advise patients that calcium channel blockers also reduce blood pressure but this class was not studied because these drugs are vasodilators that may increase headache.
Moreover treatment with each of the four classes of drugs -- thiazides, beta-blockers, angiotensin converting enzyme (ACE) inhibitors, and angiotensin II receptor agonists -- reduced the prevalence of headache (P<0.001), according to findings reported in Circulation, Journal of the American Heart Association.
“We are not saying that these drugs should be taken solely to prevent headaches, but this is a valuable associated benefit,†said epidemiologist Malcolm Law, M.Sc., M.B.B.S., at Queen Mary’s School of Medicine and Dentistry of the University of London.
Dr. Law cautioned that the data don’t answer an essential question: do headaches disappear as blood pressure drops or is there a separate and unique pharmacological mechanism in each of these drug classes, which could explain the headache benefit.
He said the link between blood pressure and headaches has been a “medical mystery for about 100 years.â€Â
“The conclusion that the blood pressure-lowering drugs prevent headache is firm, and the conclusion that a higher blood pressure causes headache is likely but not corroborated by the observational studies (generally cross-sectional in design) on blood pressure and headache,†Dr. Law and colleagues wrote.
There was a statistically significant dose-response relationship for diastolic pressure. In trials in which diastolic pressure was lowered by more than 5 mm Hg the reduction in the prevalence of headaches was 13% greater (95% CI 5 to 20, P=0.01) but this was driven by the results of a single, large trial. When the results of that trial are omitted, the relationship between decrease in diastolic pressure and headaches is of borderline significance (P=0.06).
The authors analyzed data from 94 clinical trials conducted from 1966 through 2001. The authors specifically excluded trials of calcium channel blockers because those drugs are known to cause headache. All included studies were double-blind trials of treatments of at least two weeks in duration.