A single dose of aspirin can bring at least temporary pain relief to about half of people with migraines, a new research review suggests.

Research shows that about half of people with migraines opt to use over-the-counter pain relievers only, with aspirin being a common choice. But it has not been clear exactly how well aspirin performs, or where it fits into the migraine treatment arsenal.

In the new review, UK researchers analyzed 13 clinical trials in which patients were randomly assigned to treat their migraine attacks with either a single dose of 900 to 1,000 milligrams (mg) of aspirin or a comparison treatment - either a placebo or an active drug, usually the prescription migraine drug sumatriptan.

Overall, the review found, 52 percent of aspirin users got at least some pain relief within two hours - meaning their pain was reduced from moderate to severe to “no worse than mild.” That compared with 32 percent of those using a placebo.

Similarly, one-quarter of aspirin users were pain-free within two hours, versus 11 percent of placebo users.

Aspirin also appeared to reduce some of the other symptoms that can come with migraine attacks, including nausea and sensitivity to light and sound. But a combination of aspirin and the anti-nausea medication metoclopramide - marketed as Reglan - worked even better, the researchers report in the Cochrane Database of Systematic Reviews.

Across two studies, for instance, 46 percent of patients who used aspirin plus 10 mg of metoclopramide got relief from vomiting within two hours, compared with none of those given a placebo.

Still, aspirin - with or without metoclopramide - is no magic bullet, said Dr. R. Andrew Moore, one of the researchers on the review.

“For about half of people with migraine, aspirin will help at a level of pain relief that is useful. For half it will not,” Moore, of John Radcliffe Hospital in Oxford, told Reuters Health by email.

“No medicine for migraine works in everyone,” he added, “and for the individual the key is finding that medicine - and formulation - that works for them.”

The review also found that the short-term relief from aspirin often did not last. Three studies looked at 24-hour pain relief among patients who partially improved within two hours; 39 percent had sustained pain relief for a full day, compared with 24 percent of placebo users. No study assessed 24-hour relief among people who were pain-free within two hours of taking aspirin.

In addition, while aspirin plus metoclopramide was similarly effective against symptoms as a 50-mg dose of sumatriptan, the prescription drug seemed to work better against pain when taken at a 100-mg dose. Across two studies, 28 percent of sumatriptan users were pain-free at two hours, versus 18 percent of those using aspirin and metoclopramide.

According to Moore, “it’s useful to know” that an over-the-counter pain reliever works for some people’s migraines. And that’s especially true, he noted, for people in developing parts of the world, since aspirin is cheap and readily available.

“But,” he added, “no one suffering frequent headaches should just self-medicate - it’s always better to see your primary care physician for a chat.”

People should also be aware that aspirin, like any medication, carries a risk of side effects. Used regularly, Moore noted, the drug may lead to problems like ulcers and gastrointestinal bleeding, and older adults - who are at increased risk of such problems - should be particularly cautious about frequently using aspirin for pain relief.

Moore said that parents should also avoid using aspirin for children’s migraines. Aspirin, when used by children and teenagers with chickenpox or flu-like symptoms, is associated with Reye’s syndrome - a rare but serious condition marked by brain inflammation. It’s generally recommended that parents talk with their doctor before giving aspirin to a child younger than 12.

SOURCE: http://www2.cochrane.org/reviews/en/ab008041.html Cochrane Database of Systematic Reviews, online April 14, 2010.