Meloxicam

Side effects

Meloxicam use can result in gastrointestinal toxicity and bleeding, headaches, rash, and very dark or black stool (a sign of intestinal bleeding). Like other NSAIDs, its use is associated with an increased risk of cardiovascular events such as heart attack and stroke. It has fewer gastrointestinal side effects than diclofenac, piroxicam, naproxen, and perhaps all other NSAIDs which are not COX-2 selective. Although meloxicam inhibits formation of thromboxane A, it does not appear to do so at levels that would interfere with platelet function.

A pooled analysis of randomized, controlled studies of meloxicam therapy of up to 60 days duration found that meloxicam was associated with a statistically significantly lower number of thromboembolic complications than the NSAID diclofenac (0.2% versus 0.8% respectively) but a similar incidence of thromboembolic events to naproxen and piroxicam.

Cardiovascular side effects

Persons with hypertension, high cholesterol, or diabetes are at risk for cardiovascular side effects. Persons with family history of heart disease, heart attack, or stroke must tell their treating physician as the potential for serious cardiovascular side effects is significant.

Mechanism of action

Meloxicam blocks cyclooxygenase (COX), the enzyme responsible for converting arachidonic acid into prostaglandin H₂—the first step in the synthesis of prostaglandins, which are mediators of inflammation. Meloxicam has been shown, especially at its low therapeutic doses, selectively to inhibit COX-2 over COX-1.

Meloxicam concentrations in synovial fluid range from 40% to 50% of those in plasma. The free fraction in synovial fluid is 2.5 times higher than in plasma, due to the lower albumin content in synovial fluid as compared to plasma. The significance of this penetration is unknown, but it may account for the fact that it performs exceptionally well in treatment of arthritis in animal models.

Veterinary use

Meloxicam is also used in the veterinary field, most commonly in dogs and cats, but also sees off-label use in other animals such as cattle and exotics. The U.S. Food and Drug Administration sent a Notice of Violation to the manufacturer for its promotional materials which included promotion of the drug for off-label use. In the U.S. the drug is indicated for management of pain and inflammation associated with osteoarthritis in dogs only. In Europe, where the product has been available since the early 1990s, it is also prescribed and licensed for other anti-inflammatory benefits including relief from both acute and chronic pain in dogs. Side effects in animals are similar to those found in humans; the principal side effect is gastrointestinal irritation (vomiting, diarrhea, and ulceration). Rarer but important side effects include liver and kidney toxicity.

Since 2003, the oral (liquid) formulations of meloxicam have been licensed in the U.S. for use in dogs only, with the January 2005 product insert specifically warning in bold-face type: "Do not use in cats." An injectable formulation for use in dogs was approved by the FDA in November 2003, with a formulation for cats, for surgical use only, approved in October 2004.

In the U.S., per the manufacturer's clinical instructions as of July 2010, injectable meloxicam is indicated in operative use with felines as a single, one-time dose only, with specific and repeated warnings not to administer a second dose. In June 2007, a new oral version of meloxicam was licensed in Europe for the long-term relief of pain in cats. As of June 2008, meloxicam is registered for long-term use in cats in Australia, New Zealand, Canada, and throughout Europe. A peer-reviewed journal article cites feline overdose of NSAIDs, including meloxicam, as being a cause of severe kidney damage in cats.

The pharmacokinetics of meloxicam have been investigated in koalas (Phascolarctos cinereus).

Meloxicam has been investigated as an alternative to Diclofenac by the RSPB to prevent deaths of vultures.