Previcox vs. Equioxx for Horses

Previcox vs. Equioxx for Horses

Recently there has been a discussion on the Express Veterinary Pharmacy Facebook page about using Previcox in horses instead of Equioxx. I wanted to see if I could clear up some of the confusion regarding the legalities of this as well as the cost issues.


 The United States Food & Drug Administration regulates drug use in people and animals. The FDA determines how doctors and veterinarians can prescribe drugs and medications. Before drugs are brought to market, they must undergo extensive (and expensive) testing to be sure that they are safe and that they do what they are marketed to do. The FDA reviews these tests and approves ones that pass. The maker of the drug then puts on the label what the drug is approved for (including conditions it treats and what animals were tested). This is the “label use”. A law passed by Congress in 1994 gave US veterinarians the right to use drugs in an “extra-label” manner. So vets can legally prescribe drugs for species or conditions that are not on the label.

The law said that extra label drug use could happen if one of several conditions were met, including: 1) There must be no other drug labeled for that use in that species, 2) There is a drug for use in that species, but it doesn’t have the active ingredient we need, 3) A drug is approved, but it doesn’t exist in the required concentration (mg) or dosage form (paste vs. tablet vs. IV or IM), 4) The vet has found that the labeled drug doesn’t work the way he or she needs it to work.

Vets can legally use an extra label drug if only one of the above conditions is met. As an example, before the tablet form of Equioxx came out, vets could prescribe Previcox tablets for horses because the only approved horse drug was Equioxx paste.

The appropriate dose of Firocoxib (the active ingredient in Previcox and Equioxx) for a normal sized horse is 57 mg. Since the 57 mg tablets of Equioxx came out, veterinarians have the appropriate dosage form (tablet) in the correct concentration (57 mg) in a labeled drug. Therefore, vets cannot legally prescribe either 57 mg or 227 mg Previcox for use in horses.

The FDA isn’t the only worry for veterinarians. They also have to worry about paying for lawsuits that may occur in the course of our practice. All vets carry insurance to pay for lawsuits. Thankfully, most of them don’t ever get sued, but it can happen. Some of these lawsuits cost upwards of $100,000 to defend. The pertinent point here is that the insurance policies will not cover vet's lawsuit costs if we use an extra-label drug improperly. So if a vet prescribes 227 mg Previcox for your horse, and you sue her because he died, her insurance company can refuse to cover her costs. Most vets won’t take that risk because it could ruin them financially!


 All of the costs referred to here are from the Express Veterinary Pharmacy website as of January 2018. The cost from your veterinarian may be 30-50% higher.

Treatment with 57 mg Equioxx tablets costs $1.20 a day if you buy the 180 count bottle. If you were to use 57 mg Previcox tablets it would run $1.22 a day (180 count bottle). It would be cheaper to use the 57 mg Equioxx tablets.

The equation changes if you compare the 227 mg Previcox tablets to the 57 mg Equioxx tablets. If you use the 227 mg tablets, you would break them into fourths and use a fourth a day. It would cost about 64 cents a day to use the 227 mg Previcox tablets. So the cost is about ½ if you and your veterinarian decided to use the 227 mg tablets. As mentioned above, this would not be legal and would put the veterinarian that wrote the prescription at risk.

I hope this provides helpful information on this tricky topic. Thanks to everyone who posted comments on Facebook about this! If you have any other issues like this that you would like us to address, leave a comment or post to Facebook.