Arcoxia (etoricoxib) is a therapy marketed by Merck to manage the symptoms of joint pain and swelling that accompany osteoarthritis (OA), rheumatoid arthritis (RA), gouty arthritis, and ankylosing spondylitis (AS). It is approved in many countries around the globe but it is not approved by the U.S. Food and Drug Administration. (FDA)

How Arcoxia works

Arcoxia is a nonsteroidal anti-inflammatory drug (NSAID) but has a distinctly different mechanism of action than traditional NSAIDs such as ibuprofen or naproxen.

All NSAIDs work by blocking the actions of cyclooxygenase (COX) enzymes. COX enzymes promote reactions that increase the production of prostaglandins, chemicals that cause pain and inflammation at sites of injury. Blocking COX enzymes means fewer prostaglandins will be made, therefore reducing joint pain and swelling.

Traditional NSAIDs block the actions of two types of COX enzymes, COX-1 and COX-2. COX-1 contributes to inflammation but it also helps protect the lining of the stomach, so blocking COX-1 makes the stomach vulnerable to injury. Arcoxia mainly blocks COX-2, so it is less likely to cause stomach ulcers associated with other NSAIDs.

Arcoxia in clinical trials for AS

One of the first studies to document the effectiveness of Arcoxia in individuals with AS was published in 2005.  The randomized, double-blind trial found that 90 mg and 120 mg doses of Arcoxia relieved pain and improved function more effectively than placebo, with about the same safety profile as naproxen. The study supported Arcoxia’s approval for the treatment of AS in the U.K.

A more recent Phase 3 randomized, multicenter clinical trial (NCT01208207) also compared the efficacy and safety of different doses of Arcoxia in patients with AS. The results, published in the scientific journal BMC Musculoskeletal Disorders in 2016, showed that both 60 mg and 90 mg doses of the drug controlled pain in patients with AS, establishing 60 mg as the lowest effective dose for most patients.

Additional information

Arcoxia is not approved in the U.S. because of concerns about cardiovascular risks associated with selective COX-2 inhibitors. COX-2 inhibitors can increase blood pressure and may damage the lining of blood vessels,  increasing the risk of strokes and heart attacks.

In 2007, Merck received  a non-approvable letter from the FDA in response to their new drug application (NDA) for Arcoxia to treat symptoms of OA. The FDA said they needed more evidence to show that the benefits of Arcoxia outweigh its risks.

The relative risks of Arcoxia compared to traditional NSAIDs have been the subject of multiple studies. The goal of the Multinational Etoricoxib and Diclofenac Arthritis Long-term (MEDAL) study was to more clearly define the relative risks and benefits of Arcoxia. Studies have found that traditional NSAIDS also increase the risk of cardiovascular disease, which varies according to the particular NSAID.  The risk is greatest when high doses are used over a long period of time.

Where approved, Arcoxia is administered as a tablet once a day on an as-needed basis. Dosing information allows 60 mg to 90 mg per day for managing symptoms of AS, but patients should use the lowest dose needed to control symptoms.

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