The class of painkillers that includes ibuprofen and naproxen seems to work well against menstrual cramps, and may be more effective than acetaminophen, a new research review suggests.

The medications, collectively known as non-steroidal anti-inflammatory drugs (NSAIDs), are widely used for various aches and pains, but it has been unclear how they stack up against acetaminophen - the active ingredient in Tylenol and certain other brand-name pain relievers and fever reducers.

Acetaminophen, which is known as paracetamol in several countries, is also a component of a number of products marketed specifically for menstrual symptoms.

In the new review, researchers analyzed 73 clinical trials from 18 countries that tested various NSAIDs and acetaminophen for menstrual cramps. Across the studies, women given NSAIDs were 4.5 times more likely to report “at least moderate” pain relief than those given a placebo, or inactive pills.

They were also nearly twice as likely as acetaminophen users to report such improvements - though that finding was based on only three studies, the researchers report in the Cochrane Database of Systematic Reviews.

The journal is published by the Cochrane Collaboration, an international organization that evaluates medical research.

“Our review shows that NSAIDs are a highly effective treatment for menstrual cramps,” said Jane Marjoribanks, a researcher with the Cochrane Menstrual Disorders and Subfertility Group in Auckland, New Zealand.

Exactly why they might be even more effective than acetaminophen is unclear, she told Reuters Health in an email.

That said, the effects of NSAIDs varied from study to study. The one trial that compared aspirin to a placebo showed no clear benefits from the drug; in contrast, a study on the NSAID indomethacin found that women using the drug reported good pain relief during 42 of 90 menstrual cycles, versus 9 of 90 cycles among those using a placebo.

The trials also looked at a range of NSAIDs, including ibuprofen (found in brands like Advil and Motrin), naproxen (Aleve and other brands) and diclofenac (Voltaren and other brands). And there was not enough evidence to show whether any one NSAID was more effective or safer than others, according to Marjoribanks and her colleagues.

In addition, while NSAIDs are over-the-counter drugs, they carry a risk of side effects and need to be used with caution.

Across the trials in this review, women using NSAIDs were 37 percent more likely to report side effects like indigestion, drowsiness, dizziness and headaches than women given placebo pills.

To help minimize side effects, Marjoribanks said, women should take the drugs only for a few days during each menstrual cycle - the days when pain peaks - and should not exceed the recommended dose on the packaging.

SOURCE: Cochrane Database of Systematic Reviews, January 2010.