Hi - Does anyone know how much Previcox a 1200 pound horse could have prior to a USEF rated show? I have heard that they can't have any at all and then I have heard that as long as they have only one pill or dose at least 12 hours prior to showing that they would be within the legal limit allowed if drug tested? Any information would be helpful, I am not looking to go to a rated show with an illegal horse, thanks!
Previcox per say is not legal. Equioxx is the only approved formulation of firocoxib for use in horses.
For Equioxx, a 1,000# horse can have 45.5 mg orally up to 12 hr prior to competition. (45.5 mg/1,000# = 0.1 mg/kg)
Regarding Previcox though....
1) I don't know what size pill you are using.
2) I don't know if the bioavailablity of firocoxib in the pill form is the same in the horse as the paste formulation of Equioxx
3) Since I don't know if the bioavailability is the same, I also don't know if the pharmocokinetics, ie the half life and duration of the pill formulation, of the pill is the same as the paste formulation.
If want to take your chances and ASSUME that 45.5 mg of Previcox = 45.5 mg of Equioxx, then you can give it up to 12 hr prior to competition.
The answer I gave is basically the answer you will get from them.
Previcoxx is not an approved drug for horses.
Go to http://www.usef.org/issuu/flipbook.a...elines2012.pdf. See the bottom of page 7. "Caution is urged when using compounded medications with varying administration routes not specified above. Only the above administation routes with non-compounded medications have been evaluated for the dose and time recommendations."
So, by using Previcox instead of Equioxx, you shouldn't be cited for a forbidden substance (assuming USEF rules, not FEI), but you are taking a chance with being over the therapeutic level of 45.5/1000# because of the reasons Meghan cited.
Neither formulation has a time release component which might change the metabolism and therefore the plasma concentration.
However, there is a difference in the means of administration. It seems like USEF probably does not want to state one way or the other, as research has not been done on Previcoxx administration, and absorption, in horses. They are not going to extrapolate. Or condone any type of off-label use of a drug, I would imagine.
Therefore, the OP is here, asking for COTH opinions.
The half life does not change as that is a property of the drug (firocoxib) not the "carrier"/pill or paste.
Formulation can and does change the half life of a product. Route of administration can also change that. The excipients used for the paste are likely different that those used with the pill, and may change the bioavailability, absorption and clearance of the API (in this case firocoxib). The problem is, no one knows for sure so you are taking a risk that concentrations in your horse may be above "acceptable" limits when using previcox vs. equioxx.
Thanks for all of the helpful information, I appreciate it! I wasn't going to give him any at all, but after reading more about it I think I will be safe giving him half a pill with his dinner the night before the show. I'm not showing until the last class of the day and the pill only lasts for 24 hours so I think I will be fine even if I was to give him the entire pill but I guess it's better to be safe then sorry I have also heard that there are cheaper forms of Previcox safe to give to horses, has anyone ever used them or looked into them?