Review finds evidence gaps for acetaminophen use in equids
Bottom line
Version 1
A new structured scoping review in Equine Veterinary Journal takes stock of what’s actually known about acetaminophen use in equids and lands on a cautious conclusion: pharmacokinetic data are relatively solid, but clinical evidence for analgesic efficacy is still thin. The review, by Francisco Medina-Bautista, Juan Manuel Serrano-Rodríguez, and María del Mar Granados, maps the published literature on analgesic use, safety, and pharmacokinetics in horses and related equids, highlighting a gap between how often the drug is used in practice and how limited the trial evidence remains. Supporting studies the review draws on include repeated-dose safety work in adult horses and small efficacy studies in lameness and foot-pain models, but the overall evidence base is still narrow. (pubmed.ncbi.nlm.nih.gov)
Why it matters: For equine veterinarians, the review is a useful reminder that acetaminophen may be a reasonable adjunct or alternative when conventional NSAIDs are a concern, especially given published safety and pharmacokinetic data at studied oral dosing regimens. But it’s not yet backed by the kind of large, real-world clinical trial evidence that would support broad, confident adoption as a standalone analgesic across indications. Reviews of equine NSAID practice and AAEP conference research have similarly framed acetaminophen as promising, but still short on definitive efficacy data, particularly for chronic musculoskeletal pain and combination protocols. (beva.onlinelibrary.wiley.com)
What to watch: The next step is better-powered clinical trials in horses with naturally occurring pain conditions, along with clearer guidance on where acetaminophen fits relative to, or alongside, standard NSAID protocols. (beva.onlinelibrary.wiley.com)
Key facts
- Study type
- Structured scoping review
- Journal
- Equine Veterinary Journal
- Topic
- Acetaminophen use in equids
- Main finding
- Pharmacokinetic evidence is relatively robust, but clinical efficacy data are sparse
- Scope
- Analgesic use, safety, and pharmacokinetics in horses and related equids
- Clinical takeaway
- The drug may fit best as a case-by-case option, not a routine standalone analgesic
- Evidence gap
- Larger trials in horses with naturally occurring pain are still needed
Version 2
A new scoping review in Equine Veterinary Journal is putting a more evidence-based frame around a drug many equine clinicians already use: acetaminophen. The review examines the published literature on analgesic use, safety, and pharmacokinetics in equids and concludes that while pharmacokinetic evidence is comparatively robust, clinical trial data remain sparse, leaving important questions unanswered before the drug can be more widely embraced as a routine analgesic in horses. (pubmed.ncbi.nlm.nih.gov)
That conclusion reflects a familiar tension in equine practice. Acetaminophen has attracted interest in part because long-term or repeated NSAID use in horses can carry gastrointestinal, renal, and other safety concerns, creating demand for additional pain-management tools. Prior reviews of equine orthopedics and NSAID use have described acetaminophen as a potentially useful multimodal option with a relatively favorable safety profile, but they’ve also emphasized that the evidence base is much smaller than for established equine NSAIDs. (beva.onlinelibrary.wiley.com)
The underlying literature the review appears to synthesize is still limited in both size and scope. A 2020 Equine Veterinary Journal study reported safety and pharmacokinetic data for repeated oral dosing at 20 mg/kg in adult horses over 14 days. A 2023 study in the same journal evaluated pharmacokinetics and clinical efficacy in adult horses with mechanically induced lameness. Earlier AAEP-presented work also suggested acetaminophen could provide foot-pain analgesia comparable to oral flunixin in an experimental model, while later AAEP proceedings described 30 mg/kg oral dosing every 12 hours for 21 days as safe, but not suitable as monotherapy for analgesia in horses with chronic lameness. Taken together, that helps explain the review’s central message: there’s enough signal to justify interest, but not enough clinical evidence to settle the question. (pubmed.ncbi.nlm.nih.gov)
Other published work has added detail without fully resolving the clinical picture. A 2024 Equine Veterinary Journal paper focused on naturally occurring chronic lameness, and a separate 2023 study looked at ocular penetration after oral dosing, reinforcing that researchers are still defining not just whether acetaminophen works in horses, but where it may be most useful. Review articles have also noted that, although combination or alternating therapy with NSAIDs is discussed anecdotally, formal studies on safety and efficacy of those strategies in horses are still lacking. (beva.onlinelibrary.wiley.com)
Industry and expert commentary around acetaminophen in horses has been similarly measured. AAEP proceedings have described the drug as safe at studied doses, but have stopped short of endorsing it as a standalone answer for equine pain. Broader equine pharmacology reviews have characterized acetaminophen as promising, inexpensive, and potentially useful when NSAIDs are contraindicated or when clinicians are trying to reduce NSAID exposure, while also stressing the need for caution because equine-specific efficacy data remain limited. (aaep.org)
Why it matters: For veterinary professionals, this review is less about a new therapeutic breakthrough than about calibration. It supports the idea that acetaminophen has a growing pharmacology and safety foundation in horses, which may reassure clinicians already considering it in select cases. At the same time, it argues against overconfidence. In practice, that means acetaminophen may still fit best as a case-by-case option, particularly when NSAID risks, comorbidities, or multimodal pain-management goals make alternatives attractive, rather than as a default replacement for better-studied equine analgesics. (pubmed.ncbi.nlm.nih.gov)
The review also underscores a broader evidence problem in equine pain medicine: common clinical use can outpace the published data. For clinicians, that gap matters when discussing expectations with pet parents, documenting rationale for off-label choices, or building longer-term pain plans for horses with orthopedic disease, laminitis, or other chronic painful conditions. The strongest current evidence appears to support cautious use within studied dosing ranges, but not broad extrapolation across all pain states or treatment combinations. (thehorse.com)
What to watch: Expect the next phase of research to focus on larger trials in horses with naturally occurring pain, head-to-head comparisons with standard NSAIDs, and more data on combination protocols, duration of treatment, and indication-specific outcomes before acetaminophen’s place in equine analgesia becomes clearer. (beva.onlinelibrary.wiley.com)