Merial recently released a new arthritis pain medication, Equioxx, which works similarly to phenylbutazone or flunixin meglumine (Banamine). The active drug is firocoxib, a nonsteroidal anti-inflammatory drug (NSAID). The same drug in chewable tablet form for dogs was approved in 2004 and put on the market in 2005.

The drug is approved for use for up to 14 consecutive days and sold in single-dose paste syringes that are administered once daily. It has a long half life of 30 to 34 hours, which results in blood levels continuing to slowly rise over the first six to seven days of treatment.

Effectiveness
Efficacy studies showed daily treatment with Equioxx for 14 days resulted in improvements in lameness, joint swelling, range of motion of the joint and pain on manipulation of the joint (e.g. flexion), equivalent to results obtained with a dose of 1 gram of phenylbutazone per 500 lbs.... of body weight.

Drug Interactions
• Do not combine this drug with other drugs of the NSAID class. Combining NSAIDs has the potential to greatly increase the risk and severity of side effects.
• Don’t combine with corticosteroids, which have similar side effect.
• Combination with diuretics may increase the risk of kidney-related side effects.
• Use with caution in combination with other drugs that have the potential for kidney side effects, such as the -mycin group of antibiotics.
• Using at the same time as other drugs which are highly bound to blood proteins may increase the risk of side effects of one, or both, drugs.

Precautions
This drug should not be used in horses with pre-existing gastrointestinal tract ulcers. Hypersensitivity to the drug, or to other NSAIDs is also a contraindication to use.

Horses with heart disease, liver disease, kidney disease or dehydration are likely at higher risk of side effects such as kidney damage, edema, intestinal tract ulceration. Note: Safety in young horses, pregnant or lactating mares has not been determined.

Bottom Line
Equioxx is equivalent to moderate dose phenylbutazone (2 grams/day for a 1000-pound horse) in relieving signs of osteoarthritis. The risk of oral ulcerations from the drug may be somewhat higher than with other NSAIDS, possibly because the paste is deposited in the mouth. The risk of kidney damage appears to be about the same as with other NSAIDs. The risk of ulceration in the stomach or other intestinal side effects appears to be significantly lower than with phenylbutazone. However, NSAIDs should not be used in any horse that has intestinal tract ulceration.

Equioxx’s pricey, compared to bute, retailing at $9 to $11 per dose. Bute costs about 50¢ a day for 2 grams. With price in mind, we think it’s mainly indicated for horses known to be sensitive to GI effects of phenylbutazone, such as horses that go off feed or show abdominal discomfort when on bute.