Loxoprofen sodium is a non-steroidal anti-inflammatory drug, or NSAID, marketed under various trade names in Brazil, Japan, Argentina and Mexico. It is not approved for use in the United States. Loxoprofen is in the same chemical family as ibuprofen, naproxen and ketoprofen. These drugs work by inhibiting enzymes that produce inflammatory chemicals in your bloodstream. Less inflammation means less pain, so NSAIDs find their greatest use among patients who suffer from acute and chronic pain.
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NSAIDs interfere with the activity of two key cyclooxygenase enzymes, called COX-1 and COX-2, which are responsible for producing prostaglandins. Prostaglandins participate in a wide array of biological processes, including activation of the inflammatory response, modulation of immune function, generation of fever, blood clotting, digestion, blood vessel dilation and constriction, fertility and labor. By blocking the production of prostaglandins, NSAIDs can interfere with these normal physiologic functions. Hence, the property that accounts for NSAIDs’ benefits is also responsible for their side effects.
Inhibition of both COX-1 and COX-2 leads to the most widespread and troublesome NSAID side effects. Therefore, a great deal of effort has been expended in a search for NSAIDs that only inhibit COX-2. These so-called “selective NSAIDs” have reduced the incidence of some adverse effects, but they carry their own burden of risks. According to the U.S. Food and Drug Administration, Vioxx and Bextra – both selective COX-2 inhibitors – were withdrawn from the market when it was discovered they significantly increased users’ risks for heart attacks and strokes.
Loxoprofen is a nonselective NSAID that inhibits both COX-1 and COX-2, so its spectrum of side effects, like those of other non-selective NSAIDs, is relatively broad. Loxoprofen is available in both oral and topical forms. Topical use may lead to localized irritation, called contact dermatitis, but only rarely does it result in systemic side effects. If you take loxoprofen orally, you may develop abdominal pain, heartburn, diarrhea, constipation, headaches, ringing in your ears or prolonged bleeding following minor injuries. Other more serious side effects may also occur.
Loxoprofen and other nonselective NSAIDs increase the risk of stomach and intestinal ulceration, and these ulcers may bleed. One 1995 study in the “Journal of Gastroenterology and Hepatology” reported that loxoprofen caused less irritation than indomethacin, another nonselective NSAID, when the two drugs were sprayed directly on the stomach lining. Because they inhibit the production of prostaglandins throughout your body, however, NSAIDs exert a systemic effect that can lead to GI ulceration. Even an NSAID that is administered intravenously can cause ulcers. Bleeding ulcers can occur without causing abdominal pain, so if you are taking loxoprofen and you develop black, tarry bowel movements or notice blood in your stool, if you become weak or dizzy upon standing or if you develop a rapid heartbeat, contact your doctor immediately.
Some prostaglandins help to maintain normal blood flow to the kidneys. NSAIDs interfere with the production of these prostaglandins and alter the way your kidneys function. If you already have kidney problems, high blood pressure, congestive heart failure or fluid retention, check with your doctor before taking loxoprofen.
According to a 2010 article in “Circulation, Cardiovascular Quality and Outcomes,” chronic use of some NSAIDs can increase your risk for heart attack or stroke. (See Reference 3) You should not take loxoprofen or any other NSAID unless it is indicated, and people with health problems should only take NSAIDs under the supervision of a physician.