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We Are Flying Solo

April 6, 2020

Bute Vs. Equioxx: Tradeoffs

Because it's a good time to learn about things, right?

I recently had the unfortunate but useful opportunity to compare the results of the two most commonly used equine NSAIDs (Non-Steroidal Anti-Inflammatory Drugs; bute & Equioxx) on the same injury -- Echo's shoulder.  There are pros & cons to each.  Because I firmly believe in making the most informed decisions possible, let me share with you what I learned.


Heat, pain, & swelling are the result of the body's inflammatory cycle.  One of the primary mediators of this cycle is a group of prostaglandins created by cyclooxygenase (COX) enzymes, which convert a substance interestingly named arachidonic acid (does it have spiders in it?).  There are different varieties in this group, referred to by number:  horses have COX-1 & COX-2, while humans have additional variants.  NSAIDs aim to break the inflammatory cycle by inhibiting the production of these enzymes, during which the body can break down harmful prostaglandins which have already formed (which takes about 12 hrs).

As you might suspect, COX-1 & COX-2 have different functions.  COX-1 plays important roles in things like maintaining stomach mucous coatings, keeping blood flowing through kidneys, & coagulating blood.  COX-2 is only found at low levels in normal tissues, but levels surge when that inflammatory process begins & COX-2 feeds that cycle. 
A simplified illustration from; click to embiggen

Bute refers to phenylbutazone, our old friend which has been around for decades.  It's cheap & fairly effective for pain management.  Given orally, it takes about 2-3 hrs to absorb from the belly & peaks in 3-5 hrs.  Persisting about 12 hrs, bute blocks both COX-1 & 2 production.

Equioxx is a brand name of firocoxib, a newer drug that is known in the canine world as Previcox.  It was developed for the treatment of osteoarthritis.  It's also given orally by owners, but is much slower to take effect.  It takes at least 24 hrs for levels to begin to peak & does not reach steady state for 4-6 days.  It also has a half-life of 44-46 hrs, so it takes an additional two days minimum to disappear after you stop giving it.  Firocoxib is a selective COX-2 inhibitor, which means it preferentially blocks COX-2 but still has a minor effect on COX-1.

Choices & My Observations

It just so happened that I was able to directly compare the two as Echo was on bute for the first week of his shoulder pain, then on Equioxx for a second week.  Pros & cons:

Bute Pros:
  • Much more effective pain control (side note: I've heard the same from others)
  • Significantly more rapid action - both to start & finish.  The latter can be especially important if you need to take a lame horse to the vet the next morning & you need the pain unmasked for an exam.
  • Relatively cheap
  • Easy to give -- even picky Solo will usually eat it on his food.  If they start refusing it after multiple days, I just dump it in a syringe with a little water & shoot it in their mouth.
Bute Cons:
  • Blocking both COX-1 & 2 is what brings about the higher incidence of GI issues with bute.  This is why I switched to Equioxx, as Echo had already been on bute a lot for his foot bruise & I was beginning to see ulcer signs.
Equioxx Pros:
  • Primary benefit is its selective COX-2 action:  this spares the GI tract some abuse, as well as protecting other COX-1 processes (cartilage maintenance is another one not mentioned above).
  • Also pretty easy to give as a tablet -- Echo snarfed it up when I put it in my hand with a little grain.  I've also heard of people stuffing them in cookies or gumdrops.  Just don't let other humans eat the gumdrops.  I've also heard of that happening once, LOL.
Equioxx Cons:
  • I saw significantly less pain control that definitely seemed better suited to something milder like arthritis.
  • Slow action, both to kick in & withdraw.  
  • Not cheap -- I did find (too late for me) that it was significantly cheaper online than through my vet.  Vet also did say that he did the math & it was actually cheaper per hour of pain control than bute was.  I believe him, but almost $2 a pill still hurts me.
Related note:  Equioxx & Previcox are both firocoxib.  Because Previcox can be cheaper, many people use it for their horses & just divide pills themselves.  However, be aware, it is now illegal, through the FDA, for a vet to give Previcox for a horse.  This is because accurate dosage for firocoxib is important to avoid adverse effects & it's very easy to over- or under-dose when manually dividing dog tablets.  This legal change occurred around 2016, when the tablet form of Equioxx became available; here is a good explanation.  I'm not going to call the drug police on you, just informing. 

One more note:  I learned from the Equioxx package insert that all NSAIDs have the potential to also block the prostaglandins which control body temperature.  This isn't common, but is something to keep an eye on if something goes awry.

Take Homes

Just like pretty much all of life, there are tradeoffs with each option, but I hope this will help you better understand which might work best for you.  I still consider bute my first line tool in acute pain control due to its strength & speed.  However, if you need to give an NSAID for a long period of time or are treating a horse who already has ulcers, Equioxx may be a more appropriate choice to protect GI tracts.

If you really want to dig in, here is a really nice paper from the Journal of the American Vet Med Association from 2017 on the COX enzymes & use of selective COX-2 inhibitors.


  1. Thanks for the excellent information!

    So - I used to split some of my (insanely expensive) dog and cat meds - buying the highest weight dosage, calculating per animal weight, and dividing. The vet said this could possibly result (or they can't guarantee that it won't result) in mis-dosing. Wouldn't crushing the meds (mortar and pestle style), mixing and dissolving into a liquid, and then dividing the dosed liquid solve that issue? And yes, that sounds like a bit of work to save money but these days...

    1. I totally hear you on $$, but technically, no it would not, unless you could verify that you were able to maintain a perfectly even suspension of the firocoxib in the liquid, so it could actually be much worse. Even if you did it by weight using a lab-grade scale, there are other binders & flavors in the tablets, so it is not just pure firocoxib and without access to a chromatograph, you don't know how evenly it's distributed. Even in a whole tablet, all the active drug may actually be clumped unevenly from time to time.

      The consequences of this will also vary by drug. It may differ a little if you are, say, dividing dog medicine to give to a dog (I think that's what you meant?) - your vet correctly covered their liability by informing you that this can introduce error, which can have consequences. After that, it's up to you to decide the risk level you are comfortable with for your situation.

  2. I should clarify - the meds I divided were flea and tick pills for dogs and cats, which are dosed by weight. And that was originally recommended by my long term vet in that practice, and then was contradicted by another vet in the same practice.

    So - how do pills that come scored for splitting factor in? I’ve gotten a number of prescriptions over the years that were intended for half doses. Aspirin comes to mind, as well as Apoquel that my JRT needs...

    1. Gotcha, that makes sense. That's a really good question. I think that delves into pharma production QA/QC -- there would have to be some check that they could produce a high enough % of consistency in individual tablet distribution. Which is probably also related to how many things are actually in the tablet & how they interact. Which could get complicated in a hurry. If you had a 1:1 ratio for your binder, say each molecule of binder would consistently hold one molecule of drug, that's manageable. But I suspect that is easier said than done. I am just speculating now, so caveat. Fortunately, this is why drugs have those big instruction sheets which identify where it is safe to do that.

      And to be clear, I don't think it very likely that anyone will kill their horse by cutting up some Previcox. If I were managing arthritis in an old horse, that's relatively low risk. In an animal with kidney concerns or other elevated risk factor, I'd be more cautious. I'd also advise caution if considering asking vets for Previcox these days, just because you are technically asking them to risk their license & I wouldn't want that to blow up in anyone's face just because they didn't know.

  3. Isn't the fact NSAIDs block the prostaglandins the reason why we usually use them to help control fevers?

    On an aside when I was 14 I ate some bute on a dare to see if it actually tasted like Cherry. lol

    1. My understanding is that these NSAIDs are blocking those enzymes which control the inflammatory process, which is where a fever comes from. The particular prostaglandins which control core body temperature are different, I believe (I'd have to do some research to verify). That would be why the NSAID can knock out a fever, but generally doesn't stop a body from still maintaining its normal temp.

      I have not tasted bute yet, thanks for saving me the trouble, haha! I did taste Cool Calories because it smelled like bubble gum -- it does NOT taste like bubble gum, it tasted like nasty dirt, blech.