21 Jul 2026
Kate Loomes BVSc(Hons), MSc, CertAVP(EP), CertAVP(VA), CertAVP(EM), DipECVAA, MRCVS summarises recent developments for equine analgesic provision and methods of pain assessment.
Kate Loomes
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Pain management is among the most important therapeutic objectives within the veterinary profession (Rønnow Kjærulff and Lindegaard, 2022). The recognition and assessment of pain in horses remain fundamental yet challenging aspects of equine clinical practice and welfare (Hopster et al, 2026).
Analgesia management needs to be tailored to the individual patient and can be affected by the nature of the condition being managed, the predicted time frame expected for resolution or improvement, and concurrent conditions which may influence the choice of agents. Additionally, the practicalities of analgesia provision can be influenced depending on whether the horse is in a hospital or field setting.
The BEVA primary care clinical guidelines for analgesia provide a reference point to guide clinicians (Bowen et al, 2020). The guidelines combine modern systematic review of the published evidence and expert opinion on the provision of analgesia for a range of clinical scenarios. During the development of these guidelines, the panel recognised that “pain has a significant impact on animal welfare and therefore analgesia can have assumed benefits to the individual animal, although the safety aspect of such medications must be considered alongside these potential impacts” (Bowen et al, 2020).
In horses, the potential for adverse effects associated with a number of analgesic agents can limit the utilisation of agents – particularly in situations where longer-term treatment is warranted. A multimodal approach can promote optimal analgesia by targeting different mechanisms of pain modulation, which may be beneficial in reducing the dependency on a single medication and potentially lower the risk of adverse effects.
Multimodal analgesia is the practice of using a range of analgesic drugs and methods of administration to affect as many different parts of the pain pathway as possible (Taylor and Senior, 2018).
NSAIDs exert their analgesic effect through peripheral and central modalities (Flood and Stewart, 2022). The primary mode of action of NSAIDs is via inhibition of cyclooxygenase (COX) enzymes, inhibiting the inflammatory cascade and limiting prostaglandin synthesis (Flood and Stewart, 2022). NSAIDs are probably the most common class of drugs given to horses (Taylor and Senior, 2018), and a range of NSAIDs are licensed for use in horses.
In the field setting, or when the administration is performed by the owner, NSAIDs have the benefits of a relatively wide variety of licensed products and routes of administration, as well as being familiar to horse owners (Taylor and Senior, 2018). Phenylbutazone and flunixin are considered to be non-selective NSAIDs, as they inhibit both COX-1 and COX-2 enzymes. Meloxicam and firocoxib have molecular features which are designed to more specifically target the COX-2 isoform to avoid undesirable gastrointestinal side effects (Fogle et al, 2021). Firocoxib shows a high degree of COX selectivity for COX-2 inhibition and is the first drug of the coxib category to be licensed for use in horses. Meloxicam is categorised as a COX-2 preferential, rather than a truly COX-2 selective agent (Fogle et al, 2021). An ex-vivo study found that firocoxib and meloxicam exhibited significantly less COX-1 inhibition compared to flunixin meglumine and phenylbutazone, and all drugs inhibited COX-2 (Fogle et al, 2021). The selective inhibition of COX-2 may reduce potential side effects from inhibition of the homeostatic-protective prostaglandins derived from COX-1 (Flood and Stewart, 2022). The plasma half-life of firocoxib was longer than the other NSAIDs, including meloxicam (Fogle et al, 2021).
The choice of agent and duration of postoperative administration of NSAIDs depends on the nature of the surgical procedure, and should be tailored to individual patient needs. The BEVA primary care guidelines recommended the preoperative use of NSAIDs prior to routine castration and indicated moderate certainty that an NSAID should be administered for at least three days after routine castration (Bowen et al, 2020).
A recent systematic review investigating the evidence for NSAID therapy in horses with abdominal pain found that the vast majority (80 per cent) of published studies involved flunixin (Citarella et al, 2023). After castration, one prospective study comparing the efficacy of flunixin, firocoxib or meloxicam found that postoperative heart rate was significantly higher in groups treated with firocoxib or meloxicam compared to flunixin, while respiratory rates were not different (Gobbi et al, 2020). The findings concluded that while flunixin, firocoxib or meloxicam provided effective analgesia after castration in horses, flunixin was superior (Gobbi et al, 2020).
When considering NSAID use after colic surgery, a survey of specialists in equine medicine (American College of Veterinary Internal Medicine/European College of Equine Internal Medicine) found that flunixin and phenylbutazone were the most popular NSAID choices, and that NSAIDs were typically discontinued five to seven days postoperatively in the absence of complications, but were often continued for longer where complications occurred (Gibbs et al, 2023). The survey found that 95 per cent of respondents stated the use of an NSAID would form part of their postoperative management of horses that had undergone exploratory celiotomy for colic signs (Gibbs et al, 2023). In addition to the analgesic, anti-inflammatory and anti-pyrectic properties, the anti-SIRS or anti-endotoxic properties of NSAIDs are also advantageous in horses after undergoing colic surgery (Gibbs et al, 2023).
Flunixin might be the most commonly used drug in the control of colic pain and inflammation in many situations; however, the use of non-selective NSAIDs has always been controversial in critical cases due to a high risk of adverse effects associated with their potent COX inhibition (Ziegler and Blikslager, 2020).
NSAIDs with more selective COX properties have been investigated in the literature. In an experimental setting, increased intestinal permeability to endotoxin was found when horses with experimental strangulating small intestinal lesions were treated with flunixin (Cook et al, 2009), which may be related to the inhibition of both COX isoenzymes. In horses undergoing surgery for strangulating lesions of the small intestine, one prospective study reported that firocoxib reduced a biomarker of endotoxaemia as compared with flunixin meglumine while continuing to provide similar levels of pain control (Ziegler et al, 2019). Similarly, another prospective study reported that, after colic surgery, flunixin and firocoxib have been shown to provide similar levels of analgesia in horses after surgery for strangulation of the small intestine (Keen and Shipman, 2024). In horses, both in the hospital and field setting, NSAIDs remain a very valuable agent in the provision of analgesia, and it is hopeful that ongoing research interest may be instrumental in the development of agents that provide optimal analgesia and anti-inflammatory benefits while minimising the adverse effects.
Paracetamol is a para-aminophenol derivative which is an effective anti-pyretic, but is usually referred to as a weak analgesic and weak anti-inflammatory agent (Dugdale et al, 2020a). In humans, paracetamol is a mainstay of pain management and has a relatively high margin of safety (Mercer et al, 2023). It has a weak anti-prostaglandin effect and fewer detrimental gastrointestinal effects in horses compared to NSAIDs. The action of paracetamol is centrally mediated and is thought to have effects via cannabinoid pathways, vanilloid receptors and serotonergic pathways (Dugdale et al, 2020a).
In horses, paracetamol is unlicensed for use. Clinical reports have shown promise for the use of paracetamol as a standalone or adjunctive NSAID in horses with musculoskeletal pain (Mercer et al, 2023), and the oral dose administered to horses has been revisited in the literature over the past couple of years.
One study involving horses with experimentally induced lameness reported that oral doses of 30mg/kg produced a more rapid improvement in lameness scores and heart rate compared with a dose of 20mg/kg (Mercer et al, 2023). However, the authors of this study commented that further profiling of the pharmacokinetics and safety of repeated oral dosing of paracetamol at 30mg/kg is needed to determine clinical safety (Mercer et al, 2023). The provision of longer-term analgesia for horses with chronic conditions can be challenging due to the potential risk for adverse effects associated with the use of long-term NSAIDs; for example, one study involving horses with chronic lameness reported that administration of paracetamol for 21 days (30mg/kg by mouth every 12 hours) resulted in no evidence of clinically significant changes in clinicopathological analysis, hepatic biopsy or gastric ulceration scores (Mercer et al, 2024). However, the analgesic effect appeared to be transient, and the authors of this study concluded that paracetamol may not be suitable as a monotherapy for horses with moderate to severe orthopaedic pain.
The safety of combining paracetamol and NSAIDs warrants further investigation in horses at this stage (Mercer et al, 2024). Further investigation is required to ascertain a safe and effective dose regimen for paracetamol in horses with and without concurrent NSAID therapy. An additional concern that BEVA primary care clinical guidelines highlight is the important point that, considering the genuine risks to human health from misdirection, concerns exist about the open supply of this medicine, given that sales of non-prescription medications are controlled to reduce the chance of deliberate overdose.
Local anaesthetics are the only agents that completely block sensory input, and loco-regional anaesthesia adds significantly to multimodal analgesia (Taylor and Senior, 2018).
The local anaesthetic agents used most commonly for diagnostic and surgical analgesia in horses in Europe and the US are two per cent lidocaine and two per cent mepivacaine (Schumacher and Boone, 2021). Mepivacaine two per cent is licensed for infiltration, perineural, intra-articular and epidural administration in horses. Lidocaine two per cent has been licensed for perineural and tissue infiltration, but some formulations are unavailable.
Local anaesthetics are useful for intraoperative and postoperative relief of pain, and may allow for elimination of, or a decrease in, general anaesthesia (Schumacher and Boone, 2021). Local anaesthetics block voltage-gated sodium channels and prevent neuronal membrane depolarisation. Their individual molecular structure influences properties such as tissue penetration, duration of action and risk of toxicity. In terms of molecular groups, lidocaine, mepivacaine, bupivacaine and ropivacaine are amino-amides or amide-linked molecules, and procaine and tetracaine are amino-esters or ester-linked molecules. In horses, the incorporation of a loco-regional anaesthesia technique to an analgesia plan using systemically administered agents can lead to improved analgesia (Marolf et al, 2016).
Perineural infiltration of local anaesthetic solution is used for lameness diagnostic purposes and can also be used to provide regional desensitisation for surgical procedures under standing sedation or general anaesthesia. Perineural techniques can also be used to provide postoperative or post-injury analgesia, and the use of perineural catheters has been described. Perineural infiltration of local anaesthetic via a perineural catheter at the tibial nerve was used to provide therapeutic analgesia in one horse after a degloving injury, where alternative methods of analgesia had not prevented the development of persistent pain (Marolf et al, 2016). In this case, the catheter was placed under ultrasound guidance and was maintained in place for nine days before localised swelling at the insertion site prompted removal (Marolf et al, 2016). The technique used to place continuous peripheral nerve block catheters adjacent to the palmar nerve in equine cadaver limbs has been described in vitro (Driessen et al, 2008).
One recent experimental study described the infiltration of bupivacaine via an indwelling retrobulbar catheter to treat ocular pain in horses (Moody et al, 2025). This preliminary experimental investigation into the use of retrobulbar catheters describes the technique and effect of local anaesthetic infiltration, but further studies are necessary to evaluate the safety of this technique in horses with corneal pain. Wound soaker or wound infusion catheters have also been described in the literature to provide a method of delivering regional local anaesthesia. A wound catheter is a closed-ended, thin, hollow tube with side ports in the distal portion (infusing region) and an injection port in the proximal portion (Minghella and Auckburally, 2014). One retrospective study described the use of wound infusion catheters for local postoperative infusion of bupivacaine after partial ostectomy surgery of thoracolumbar vertebral spinous processes (Wickstead et al, 2024).
Concerns have been shared relating to the placement of wound infusion catheters and seroma formation, delayed wound healing and increased wound infection; however, no differences in surgical site infection were present between horses with and without wound infusion catheters in that retrospective analysis (Wickstead et al, 2024). It is important for all local anaesthetic solutions that the dose is carefully calculated and systemic toxic ranges are not approached. A comprehensive review of loco-regional techniques of the equine head can be found by Hermans and colleagues (2019). Expert-led clinical guidelines recommend the intratesticular infusion of local anaesthetic solution during routine field-based castration in clinical practice, even during general anaesthesia (Bowen et al, 2020).
Systemic IV administration of lidocaine has been shown to produce thermal nociception, but had a minimal effect on visceral distension in an experimental setting (Robertson et al, 2005).
During general anaesthesia, IV infusion of lidocaine has been shown to reduce the inhalational agent requirement (Dzikiti et al, 2003) and may be incorporated into partial intravenous anaesthesia (PIVA). However, it is unclear whether the contribution to total anaesthetic requirements is related to central nervous system (CNS) depression or an analgesic effect of lidocaine (Robertson et al, 2005).
Indirect evidence suggests that intraoperative lidocaine infusion produces antinociception during castration in ponies (Murrell et al, 2005) and an anti-inflammatory effect in experimentally induced endotoxaemia in horses (Peiró et al, 2010). Conversely, in black walnut extract models of laminitis, systemic lidocaine at concentrations achievable in a clinical setting did not exert anti-inflammatory effects (Williams et al, 2010).
When considering specific conditions which elicit pain in horses, laminitis-related pain can significantly impact equine welfare, and the complexity of the laminitic pain profile requires thorough and repeated pain assessment as a basis for successful pain therapy (Hopster and van Eps, 2019).
Systemic lidocaine has been described in the treatment of severe laminitis with good results (Malone and Graham, 2002). In hospitalised horses with severe laminitis, infusion of IV lidocaine may be a useful agent to incorporate into a multimodal approach. In horses suffering from acute severe laminitis in the hospital setting, infusions of lidocaine and ketamine can be useful alongside systemic administration of NSAIDs and paracetamol.
In horses with hindlimb foot pain, caudal epidural administration of opioids can be useful and epidural catheters can facilitate repeated administration.
Non-pharmacological methods of providing analgesia in horses with foot pain include considerations of the floor surface and appropriate foot support.
Using these multimodal combinations may lead to a reduction in NSAID dose requirements in individual cases at different stages of the disease, reducing the risk of NSAID-related side effects (Hopster and van Eps, 2019). Administration of agents via IV infusion may not be suitable for longer term analgesia in chronic conditions, however lidocaine infusion can be beneficial during acute laminitis episodes or pre-emptively when a procedure (for example, hoof resection or other surgery) is likely to cause acute pain and may be associated with hyperalgesia (Hopster and van Eps, 2019).
Ketamine is well known for its role as a dissociative anaesthetic agent in producing induction of general anaesthesia in horses, but it can also provide analgesia or antinociception when administered at subanaesthetic doses.
The use of ketamine for analgesic purposes tends to be restricted to the hospital setting. Ketamine is a non-competitive N-methyl-D-aspartate receptor antagonist which can inhibit the action of excitatory neurotransmitter, glutamate, promoting analgesia via modulation of pain processing pathways. Ketamine may also have opioid actions which may contribute to the analgesic effect (Dugdale et al, 2020b).
Ketamine should not be used as a sole analgesic, but is most effective when utilised as part of a multimodal analgesic plan and may be particularly beneficial where the pain is thought to have a neuropathic component (Taylor and Senior, 2018). Ketamine may be administered via CRI in anaesthetised or conscious horses. The most recent phase of the Confidential Enquiry into Equine Perioperative Fatalities (CEPEF4) reported that the intraoperative administration of a ketamine CRI during general anaesthesia was associated with increased odds of fatality (Gozalo-Marcilla et al, 2025).
The authors of that study discussed that ketamine and its active metabolites may lead to CNS excitation and a negative effect on recovery quality; however, the dose and timing of ketamine infusion is likely to affect results and these were not specifically investigated (Gozalo-Marcilla et al, 2025).
This finding highlights the importance of considering the potential for excitatory effects of ketamine administration. In standing conscious horses, the analgesic properties of ketamine can be produced using very low doses of ketamine via a loading dose (0.1mg/kg to 0.5mg/kg IM or SC, followed by a CRI of 0.12mg/kg/hr to 0.5mg/kg/hr IV; Dugdale et al, 2020b). If the facility for CRI is unavailable, ketamine may be administered via intramuscular or subcutaneous injection (0.1mg/kg to 0.5mg/kg; Muir, 2009). It is not advisable to administer ketamine intravenously, as even small doses of ketamine in conscious horses may cause CNS excitation, agitation or recumbency. It is always recommended to administer a CRI via a calibrated infusion pump to ensure accurate drug administration. Ketamine and its active metabolites may be cumulative, and one study found that excitation and behavioural changes occurred after 24 hours of ketamine CRI (Elfenbein et al, 2011). The same study also documented an increase in gastrointestinal transit time and reduced faecal output after prolonged (more than 24 hours), infusion (Elfenbein et al, 2011) which should be considered as a side effect and gastrointestinal function should be closely monitored in hospitalised horses receiving ketamine treatment.
Due to the potential for adverse effects and frequency of administration, ketamine treatment should be reserved for hospitalised horses that are under close observation.
Opioids are effective in managing moderate to severe pain in horses but concerns over their adverse effects on gastrointestinal motility and associated increased colic risk may limit their widespread use (Haralambus et al, 2024).
The use of opioid analgesics in horses can be justified when the benefits of their analgesic and sedative properties outweigh the disadvantages of potential side effects (Clutton, 2010). Legislation and the controlled status of opioids mean that administration is limited to the hospital setting.
Butorphanol is a partial opiate agonist that primarily acts at kappa receptors and is frequently co-administered with alpha-2 adrenoreceptor agonists to achieve sedation in horses. Expert-led clinical care guidelines analysed existing evidence and concluded that butorphanol had limited analgesic effects in horses (Bowen et al, 2020).
Buprenorphine is a partial µ-opioid receptor agonist which is used in horses for mild to moderate pain (Taylor et al, 2016) and has a duration of around six to eight hours.
Subcutaneous administration of a high concentration formulation of buprenorphine has been recently explored in experimental settings. One study found that while this formulation has the potential to treat pain in horses, at this dose, duration of antinociceptive effects was not longer than that reported for conventional buprenorphine, and side effects, including reduction in gastrointestinal motility and increased locomotor activity, were documented (Flynn et al, 2021).
Transdermal administration has also been explored and one experimental study reported that low systemic concentrations were achieved after transdermal application compared to intravenous (Nelson et al, 2024). Bioavailability after transdermal application was 11 per cent in that study and limited thermal antinociceptive effects were observed at the transdermal doses studied (Nelson et al, 2024).
Morphine and methadone are full µ-opioid receptor agonists which have been used to provide analgesia in horses, but remain unlicensed in this species currently. For horses undergoing general anaesthesia, evidence exists to indicate that intraoperative opioids given to horses undergoing surgical procedures have negligible cardiopulmonary effects and improve recovery quality (Clutton, 2010). The opioids have been associated with reduction in gastrointestinal motility, but the extent to which they contribute is not clear. The risk of postanaesthetic colic is multifactorial, and extracting the role of opioids in the presence of confounding factors can be complex.
That being said, the administration of opioids including morphine or methadone in horses tends to be short term via a single dose to minimise the risk of disruption to gastrointestinal motility.
A recent study involving horses undergoing general anaesthesia for imaging or a variety of surgical procedures found that intraoperative or short-term (less than 24 hours) administration of butorphanol, methadone or morphine did not influence the prevalence of postanaesthetic colic (Haralambus et al, 2024). Long-term (more than 24 hours) administration of butorphanol or methadone did not increase colic risk, but long term administration of morphine did increase postanaesthetic colic risk (Haralambus et al, 2024).
The application of transdermal fentanyl patches has been investigated with varying results.
The BEVA primary care clinical guidelines for analgesia reported that the panel was unable to make recommendations regarding transdermal fentanyl until further clinical evidence of effective analgesia is produced (Bowen et al, 2020).
A recent experimental study in adult horses found that fentanyl administered via transdermal patch was well absorbed and tolerated, but failed to produce an antinociceptive effect as measured by thermal and mechanical threshold at the doses studied (Reed et al, 2024). In another experimental study, a fentanyl patch was placed in six horses over the carpometacarpal joint to investigate whether this targeted joint placement would result in a concentrating effect in the associated synovial fluid. The study reported that fentanyl concentration in the synovial fluid of the treated joint was not higher than plasma concentration and did not differ significantly from the untreated joint (Ortega McCormack et al, 2023).
Evidence to support the consistent and predictable absorption of transdermal fentanyl and analgesic efficacy in horses and foals is lacking.
Epidural administration of drugs can produce effective analgesia of a longer duration and fewer side effects compared to systemic administration (Rønnow Kjærulff and Lindegaard, 2022).
The administration of morphine via cervical epidural catheter has been investigated in an experimental setting and resulted in a longer duration of antinociception compared to intravenous morphine with no noticeable adverse effects (Hopster et al, 2022).
Caudal epidural administration of morphine or methadone has also been described and routinely utilised in equine clinical anaesthesia. Preservative-free formulations are used for this route of administration. The co-administration of morphine and methadone via caudal epidural injection in one experimental study reported significant increases in tolerance to mechanical noxious stimuli at the coccygeal, perineal, sacral, lumbar and thoracic regions (Rønnow Kjærulff et al, 2021).
In terms of adverse effects reported, the same study found some signs of decreased frequency of defaecation, generalised sweating, and pruritus in the treated horses (Rønnow Kjærulff et al, 2021). The co-administration of methadone and morphine aimed to provide a rapid onset and longer-lasting duration of effect; however, the results from that study found a slow onset of action (4.4 hours) but a relatively long-lasting analgesic effect (at least five hours; Rønnow Kjærulff et al, 2021).
A comprehensive review of caudal epidural anaesthesia and analgesia is provided by Rønnow Kjærulff and Lindegaard (2022).
Alpha-2 adrenoreceptor agonists are well known for their role as sedatives but their analgesic properties may remain underutilised. They may be administered via intravenous, intramuscular or transmucosal routes. Clinically, α2 agonists are integral for managing colic pain, reducing inhalant anaesthetic requirements during general anaesthesia and providing multimodal analgesia (Hubbell et al, 2025). In conscious horses, the sedative effect may be hard to separate from the analgesic effect.
Alpha-2 adrenoreceptor agonists have an important role in pain management for standing surgeries and postoperative pain (Taylor and Senior, 2018). Administration of α2 adrenoreceptor agonists produces analgesia via peripherally and centrally mediated pathways. Centrally, the antinociceptive effects of α2 adrenoreceptor agonists are more spinal than supraspinal and involve a reduction of substance P activity and hyperpolarisation of dorsal horn neurones (Dugdale et al, 2020b).
In horses, the use of α2 adrenoreceptor agonists for analgesia may be limited by the side effects of systemic uptake which is variable depending on the dose administered and the route of administration. While α2 adrenoreceptor agonists produce effective analgesia and sedation, they also have a number of other effects which are significant in horses.
To varying degrees and duration depending on dose, all α2 adrenoreceptor agonists have significant cardiovascular effects. After administration, a biphasic effect tends to occur, initially with vasoconstriction, hypertension and bradycardia resulting in a reduction in cardiac output, which is followed by vasodilation and decreases in blood pressure.
Other notable effects of α2 adrenoreceptor activation include decreased gastrointestinal motility, reduced insulin secretion and increased urine output (Hubbell et al, 2025).
In the field setting, α2 adrenoreceptor agonists are often used for sedation to allow safer examination and facilitate interventions; for example, in horses presenting with abdominal pain or colic. In this setting, α2 adrenoreceptor agonists are also widely recognised as valuable in the initial treatment of abdominal discomfort in the horse, usually accompanied by NSAIDs such as flunixin meglumine (Hubbell et al, 2025).
To maintain general anaesthesia, the administration of α2 adrenoreceptor agonists via intravenous infusion alongside inhalational anaesthesia, or PIVA, has gained popularity over the past decade. The inclusion of the α2 agonists, including xylazine, romifidine and medetomidine, produces an inhalant-reducing effect which may partially be due to the additional analgesic effects. Utilisation of α2 adrenoreceptor agonists in PIVA protocols was a popular choice to maintain general anaesthesia in the latest phase of the CEPEF4, where 37.4 per cent of horses received PIVA with α2 adrenoreceptor agonists (Gozalo-Marcilla et al, 2025).
Routine use of α2 agonists purely for their analgesic properties is limited due to the concurrent sedation, cardiovascular, gastrointestinal, urinary and hormonal effects.
However, methods of antagonising those “side effects” are under active investigation. Future research should aim to develop α2 agonists with potent analgesic but minimal sedative effects to improve equine pain management (Hubbell et al, 2025).
Cannabidiol (CBD) is a drug that has gained popularity in human medicine for treatment of anxiety, epilepsy, Huntington’s disease, and acute and chronic pain (Sánchez de Medina et al, 2023).
In horses, some investigation is underway exploring the pharmacokinetics and efficacy of formulations which may be administered via intravenous or oral routes (Sánchez de Medina et al, 2023). In one randomised study, mature horses with mild osteoarthritis had an improved quality of life and superior analgesia when oral transmucosal CBD oil was added to phenylbutazone therapy compared to phenylbutazone alone. The horses were assessed using the Horse Chronic Pain Scale (Interlandi et al, 2024).
Clinical evidence for CBD use in horses is in its infancy, and limitations may exist relating to legislation and regulation of products; however, potential might exist for effective use in horses, and further investigation is warranted.
The accurate assessment of pain is required to appropriately manage pain, optimise welfare and assess response and effectiveness of therapeutic intervention. Multiple pain assessment tools have been explored in the literature and their use have expanded significantly over the past few years.
Approaches include behavioural observation, facial expression analysis, ethogram-based systems, composite pain scales, gait analysis, quantitative sensory testing and condition-specific tools for foals, donkeys and postoperative or chronic pain (Hopster et al, 2026).
Effective implementation into everyday clinical practice requires a consistent approach, additional training and the use of tools specific to the clinical context or the patient subpopulation. Tools that evaluate facial expression in horses have been investigated in the literature and systems include the Equine Pain Face (Gleerup et al, 2015), the Horse Grimace Scale (Dalla Costa et al, 2014), and the Equine Utrecht University Scale for Facial Assessment of Pain (van Loon and Van Dierendonck, 2015). Composite pain scales are popular and use a combination of behavioural and physiological information. Specific scales for use after orthopaedic or colic surgery have been developed, and specific scales have also been developed for specific populations such as foals and donkeys (Hopster et al, 2026).
Consensus of equine experts concluded that, among available instruments, the Equine Pain Scale was identified as the most feasible score for routine clinical use due to its brevity, multidimensional structure and demonstrated reliability across observers (Hopster et al, 2026).
Optimal analgesic strategy needs to be tailored to the individual patient, and aspects such as severity, chronicity and comorbidities can influence analgesic options.
A multimodal approach offers the opportunity to facilitate effective analgesia, while aiming to minimise adverse effects associated with reliance on a single agent.
Further work is required to continue to expand the repertoire of effective and safe analgesic agents available for use in horses.
Kate Loomes qualified from the University of Sydney and worked in large animal practice in the UK before undertaking a residency in veterinary anaesthesia at the University of Liverpool. Kate is a European specialist in veterinary anaesthesia and analgesia, and joined the team at Rainbow Equine Hospital in 2017.