Phenylbutazone 1 gm/Scoop / Cimetidine 500 mg/Scoop

There is a wide variety of pain relievers available for horses that can help alleviate pain and discomfort associated with injury or daily exercise, and enable easier, prompt treatment of the problem at hand.

Methods of managing pain in horses range from non-steroidal anti-inflammatory drug use and opioids to α-2 agonists and ketamine, among others. Over the years, experience and research have helped veterinarians determine which of the numerous analgesics (painkillers) are most effective.¹

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) work by reducing inflammation. As the name suggests, they are not related to steroids which also reduce inflammation. NSAIDs work by reducing the production of prostaglandins, which promote inflammation, pain, and fever.

There are nearly two dozen different NSAIDs available, but they all work in the same way, and that is by blocking a specific group of enzymes called cyclo-oxygenase enzymes, often abbreviated to COX enzymes. These enzymes are responsible for the production of prostaglandins. Prostaglandins are a group of compounds with hormone-like effects that control many different processes such as inflammation, blood flow, and the formation of blood clots.²

While NSAIDs tend to get lumped into one category in the minds of most people, it’s important to remember that each drug has its own chemical composition and level at which it causes toxicity. Toxicity generally results from overdosing the horse with medication, with most episodes affecting the gastrointestinal tract, kidneys, or liver.¹

Opioids

Opioids are frequently used by veterinarians with sedatives or tranquilizers when performing procedures on standing horses. These combinations are thought to be especially useful when working around the hind legs as they seem to minimize the likelihood of the horse kicking, however, their efficacy as analgesic medications is reported to be mixed.¹

Studies suggest that pain relief is afforded by opioids for short periods of time or when given by infusion. However, some of the side effects of opioid drugs in horses–such as gastrointestinal stasis (lack of motility), and arousal (hypersensitivity to surroundings)–preclude many veterinarians from using opioid drugs in equines for minor pain relief. Generally speaking, opioids appear to be more effective when administered epidurally than when given systemically. They have also been documented to be effective for pain relief when given as intra-articular injections to humans and other domestic animals, some researchers believe that there might be a similar effect in horses.¹

α-2 Agonists

α-2 Agonists are considered by many veterinarians to be the most effective systemically used analgesics in the horse, as evidenced by both laboratory studies and clinical use, although they typically are not the first choice for analgesics as they can produce side effects including ataxia (incoordination), drowsiness, hyperglycemia (an elevated level of blood glucose), and gastrointestinal stasis, among others.¹

α-2 Adrenergic receptors are located with opioid receptors. Thus, the two drug classes used together are highly synergistic for sedation and analgesia. α-2 agonists have a versatile dosing profile. That allows low and even micro-doses in combination with opioids to be clinically useful and minimizes the cardiovascular effects. Clinicians should be mindful that cardiovascular side effects occur even with very low doses of α-2 adrenergic agonists, that lower doses will have a shorter duration of effect, and that analgesic effects have a shorter duration than the sedative effects.³

Drug Combinations and Synergy

As in anesthesia and sedation, drug combinations can offer superior treatment benefits for pain relief assuming that the synergy is not accompanied by compounded side-effects. The therapeutic value of drug combinations is ultimately based on enhancing the therapeutic window between the desired drug effect and side-effects, which is related to the difference between drug interactions in target and other cells.⁴ At present, the growing need for specialty formulations of this type is being filled by custom compounding pharmacies.

Phenylbutazone, for example, is an NSAID frequently prescribed for lameness, musculosketetal pain, muscle soreness, bone and joint problems, and laminitis in horses. Quickly absorbed into the blood stream, it produces pain relief and fever reduction quickly, thereby making the horse more comfortable. Cimetidine is an anti-ulcer medication that works as a histamine H2 receptor antagonist. It is often used to treat equine gastric ulcers, often found in foals and race horses. In combination, these medications are an easily-assimilated solution for the treatment of muscle soreness, bone and joint problems in horses.