The first pain patch using an anti-inflammatory drug to relieve acute sprains and strains is now available in the U.S. and is intended to produce fewer side effects than similar pills, maker Alpharma Inc. said Wednesday.

The Flector patch contains 180 milligrams of diclofenac, one of the world's most widely used nonsteroidal anti-inflammatory drugs. As a pill, diclofenac is sold under the brand name Voltaren.

The Flector patch, now available by prescription in drugstores across the United States, measures about 4 inches by 5 1/2 inches and is meant for short-term use.

The side effects of anti-inflammatory pills — upset stomach, nausea and potentially dangerous stomach bleeding and ulcers — are reduced with the patch because its puts less pain reliever into bloodstream, Bridgewater, N.J.-based Alpharma Inc. said.

It is applied directly to intact skin in the area of an acute injury, such as a muscle or tendon strain, bruise or joint sprain and can be reapplied every 12 hours.

The patch is not for everyone, though. People with heart disease — or risk factors for heart disease — may be at higher risk of serious blood clots, heart attack and stroke if they use the patch, and it should not be used to relieve pain after heart bypass surgery.

The product has been on sale outside the United States since 1993 and is now approved in 43 other countries.

It got marketing approval from the U.S. Food and Drug Administration just last year shortly before Alpharma acquired from a Swiss drug company the rights to sell it in the U.S.

In this country, other prescription pain patches include a powerful narcotic such as fentanyl, and those sold over the counter contain topical pain-relieving oils and gels with ingredients such as menthol and camphor.

Alpharma focuses on pain treatments for people and medicines for livestock.