2021 Convention Bonus Coverage: Acetaminophen Use for Chronic Equine Lameness

Coverage during the live 2021 AAEP Convention is brought to you by EquiManagement and is sponsored by ADM Cellarator Advantage.

iStock/Eileen Groome

Following are takeaways from the 2021 AAEP Convention topic “Pharmacokinetics, Pharmacodynamic Efficacy, and Safety of Acetaminophen in Adult Horses with Naturally Occurring Chronic Lameness” presented by Melissa A. Mercer, MS, DACVIM–LA, a resident in clinical pharmacology at the Virginia-Maryland College of Veterinary Medicine at Virginia Tech.

Huh, Who’d Have Thunk?

Part Five: Are We Oblivious to the Obvious?

What I learned today is that sometimes we can’t see the forest for the trees, appreciate things that are right in front of our faces, or think outside the box to apply what we know from one situation to another.

Because we are in Nashville, let’s take country song lyrics as an example. It’s easy to recognize a song when we hear it on the radio. Or on Spotify, YouTube or Facebook (whatever, Gen Zers; I can TikTok, too!). But what if it is just a little out of context? Like, if you are listening to it a cappella? Better yet, can you recognize a popular country song by reading only a few lines in an online article? Let’s try it and see! Answers are footnoted below.

1. Got this 737 rocking like a G6/Stewardess is somethin’ sexy/Leanin’ pourin’ Coke and whiskey

2. A bunch of good-time numbers on the stall door/A picture of you on a dartboard

3. Before you get caught on that ladder/Let me tell you what it’s all about/Find you a few things that matter/That you can put a fence around

4. And the night got deathly quiet/And his face lost all expression/Said, “If you’re goanna play the game, boy/You gotta learn to play it right

The point is, sometimes the answers we are looking for are just a tiny bit out of context and obscure enough that they become challenging to recognize.

This was highlighted during Melissa Mercer’s presentation, “Pharmacokinetics, pharmacodynamic efficacy, and safety of acetaminophen in adult horses with naturally occurring chronic lameness.”

Acetaminophen.

For chronic equine lameness.

As Mercer pointed out during her presentation, equine practitioners use nonsteroidal drugs (NSAIDs) on a pretty much a daily basis. They are, in fact, staples in the management of chronic laminitis due to osteoarthritis, laminitis, etc. But as we know, long-term, daily administration of NSAIDs are associated with important side effects due to COX-1 inhibition—namely renal papillary necrosis, gastric ulceration and right dorsal colitis. As such, having an alternative to traditional NSAIDs would be a welcome change.

Acetaminophen is one commonly used—with great success, Mercer said—in human and small animal medicine for chronic pain (e.g., osteoarthritis). In those species, acetaminophen can be used either alone or in conjunction/alternating with traditional NSAIDs. And it’s sold over the counter.

In her study using 12 horses with naturally occurring lameness, Mercer demonstrated that 30 mg/kg acetaminophen administered by mouth twice daily for 21 days is safe to use in horses.

Horses included in that study were diagnosed with AAEP grade 2 out of 5 lameness for a minimum of four weeks’ duration in one or more limbs. Those horses had a variety of painful musculoskeletal conditions, and some horses had multiple injuries. Pharmacokinetic analysis was performed on days 7 and 21 while clinicopathology, gastroscopy and liver biopsies were performed at baseline and day 22. Lameness examinations were performed without the drug (baseline) and again on day 21.

Mercer found the following:

· Maximum plasma concentrations were achieved within the first hour following oral administration;

· Squamous ulcer scores improved during the study period;

· No significant differences in clinicopathology and hepatic histology were appreciated; and

· A significant improvement in head height one hour post treatment compared to baseline was measured.

Mercer concluded that while acetaminophen may not improve lameness sufficiently to be appropriate for monotherapy, it could serve as a valuable NSAID-sparing option.

In retrospect, this answer to our NSAID problem seems so simple that Mercer reminds me of the TikTokker who makes fun of life hacks.

While writing this story I recognized that country musicians frequently sing about alcohol and devastating loss, which is funny but also slightly concerning. Supporting the Not One More Vet movement, I encourage all veterinarians struggling with substance abuse, mental health or even just something as simple as finding work-life balance to reach out for help.

Tomorrow, the final day of the 67th Annual Convention of the AAEP, brings one last opportunity for me to find something to make you say “Huh, who’d have thunk?”

Quiz answers:

1. Dierks Bentley, “Drunk on a Plane”

2. Luke Combs, “Cold as You”

3. Jordan Davis, “Buy Dirt” (feat. Luke Bryant)

4. Kenny Rogers, “The Gambler”’

About ADM Animal Nutrition and Cellarator Advantage

Demands of exercise are a stressor for the performance horse. Heavy work can overwhelm the body’s natural ability to deal with oxidative stress, which can damage muscle proteins, lipids and DNA, release pro-inflammatory cytokines leading to muscle pain, and damage the mitochondrial membrane decreasing energy production. Cellarator Advantage RECOVERY+ by ADM Animal Nutrition™ was designed to help the performance horse combat the stress of exercise. To learn more, watch this video

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