Page 127 - January 2021

VETERINARY VIEWS
Owner-administered NSAID treatment in the face of colic is a concern. Out in the field, NSAIDs tend to mask clinical signs and the severity of a colic that needs more aggressive intervention.
or not. It’s always best to err on the safe side to keep options open – have a veterinarian attend quickly to the horse to determine
if it’s appropriate to haul into a referral hospital when the horse can’t be managed appropriately in the field.
Giving a “full dose” (10 cc or 1000 micrograms (mcg)) of flunixin to a colicky horse without a veterinarian’s evaluation potentially delays appropriate treatment and worsens
the prognosis. For example, pain of a simple impaction may respond well to this amount
of flunixin, yet this does nothing to treat the primary problem – with time and without fluid therapy, an impaction often worsens. A once simple, easily remedied problem may now result in the need for colic surgery.
On an annual basis, 10% of horses experience colic. Of these, 10% need surgery. When pain-relieving medication is ineffective and/or pain returns, this puts the horse into a risk category for more extensive treatment or surgery. Even if surgical intervention isn’t an option for an owner, medical care and IV fluids are very important, particularly for impactions or mild intestinal displacements.
Some conditions, such as cecal impactions, initially develop relatively mild colic signs, but may prove fatal if NSAIDs are administered without additional treatment. Toxicity of NSAIDs may result in kidney failure and development of gastrointestinal ulcers if the horse is given a “full dose” without proper assessment of hydration status. If it is necessary to administer flunixin prior to veterinary assessment, then only give a half dose (5 cc or 500 mcg), or better yet, give only 1/4 dose (2-1/2 cc or 250 mcg). This alleviates pain without masking more serious conditions that require additional treatment. Or consider using a sedative or other pain-relieving medication discussed below.
ORAL VERSUS INJECTABLE NSAID
Treatment with any oral drug formulation takes longer to take effect than the intravenous version. While duration until onset varies between individual horses,
oral flunixin may take 1-2 hours to achieve pain-relieving effects compared to more immediate effects (10-15 minutes) with intravenous formulations. Bioavailability is slower and blood levels lower following oral
Treatment with any oral drug formulation takes longer to take effect than the intravenous version.
administration. Once an oral dose has been given, particularly a “full 1000 mcg dose,” then no more injectable NSAID can be added – this hampers the rapid IV treatment a veterinarian can provide when attending the horse.
The slow onset of action makes oral NSAIDs far from optimal for treating acute colic – clinical signs continue for a period of time before drug effects kick in. If gastrointestinal motility is reduced, as is common with an intestinal crisis, there is likely to be a corresponding slowed
effect on oral drug absorption and metabolism. Orally-administered NSAIDs normally have a prolonged half-life (4.5 – 10 hours) compared with an IV counterpart (1.5 - 4 hours). An
oral NSAID could allow a condition to go undiagnosed and untreated, thereby prolonging both treatment and cost.
Although flunixin is labeled for either IV or IM use, flunixin should never be administered intramuscularly (IM). Adverse muscle effects can occur with muscle injection of many drugs, ranging from mild swelling, heat and pain
that is resolved with hot packing and topical DMSO. But, in rare cases, intramuscular flunixin is associated with a rapidly progressive, life-threatening muscle infection – Clostridial myositis. Clostridial spores are carried by the needle inward from the skin surface. Coupled with tissue damage from the highly irritating nature of flunixin, full-blown myositis can develop. These horses become extremely toxic and are very difficult to save. IM flunixin administration is simply not worth the risk,
no matter how small the dose. The IV form
of flunixin can be administered orally if intravenous access is a problem.
Phenylbutazone, an intravenous preparation, should also never be given intramuscularly because it is extremely caustic to muscle.
In the face of a colic crisis, first gather information about the three P’s of colic: Pulse, Pain, and Peristalsis along with mucous membrane color and refill time.
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