Musculoskeletal disorders are a common problem in horses, particularly performance horses. They are also the most prevalent health problem in aging horses.1 While these may not be life-threatening, since they are painful, they remain an important welfare and husbandry issue. Musculoskeletal disorders typically affect a horse’s ability to move, with the severity of impact being dependent upon the specific problem.2 In equines, musculoskeletal injuries are a chief source of debilitating pain in horses, as well as financial loss and loss of performance. In performance horses, joint disease and tendon injuries are very common.

When musculoskeletal pain, acute or chronic, arises, the cause may lie in the bones, joints, ligaments, tendons and/or muscles or the nervous system. In the case of most horses, damage to either the bones, tendons, ligaments and/or joints are the primary causes of pain.  

Laminitis is a common and extremely painful condition that affects horses. It affects the tissues (laminae) bonding the hoof wall to pedal bone in the hoof. This sometimes results in the pedal bone sinking or rotating within the hoof under the weight of the horse.3 

Osteoarthritis is a major cause of pain and decreased performance in horses. This is an inflammation of the joints and surrounding bone which causes progressive deterioration of the affected joint or joints. While healthy joint cartilage can withstand the normal wear and tear demanded of many horses, long-term inflammation can damage the joint cartilage and other joint tissues, resulting in chronic pain.

Myopathies are disorders that primarily affect the muscle. Exertional myopathies (e.g., "tying up") are myopathies that directly involve the muscle fiber. These can directly result in joint or muscle pain, or can give rise to joint damage over time.

Tendinitis is an inflammation of the tendons. Since tendons do not stretch very much, the demands of work or performance can overstress a horse’s tendons. Occasionally, tendons can even become torn, and tend to heal slowly because they are poorly supplied with blood.2 The inflammation associated with tendinitis can also cause chronic pain.  

Bone disorders usually stem from trauma (e.g., fractures, cracks). Infections that cause bone tissue to break down can also lead to bone disorders. In other situations, diseases of the ligaments or tendons may cause secondary bone damage.2,3 The inflammation associated with bone disorders almost always gives rise to chronic pain in the horse.

Joint disorders are often caused by trauma to the joint, long-term inflammation, developmental problems, or infections. Traumatic injuries can cause dislocation, fracture, or the distortion of a joint, arthritis, or the rupture of nearby ligaments or membranes.2 

Gabapentin for Horses

Gabapentin is an anticonvulsant, anxiolytic and neuropathic analgesic. In veterinary medicine, it has been used in dogs and cats as adjunctive therapy for refractory or complex partial seizures and in many species for the treatment of chronic pain (especially neuropathic pain). It is beneficial in cats for reducing the fear response associated with handling and examination, and in dogs for storm phobia.4

Gabapentin does not appear to be effective for treating acute pain, but it may be of benefit when given before surgery for acute pain when used with other analgesics. When used preoperatively, gabapentin reduced the amount of opioids needed postoperatively in dogs.4 It has also been proposed for further study in horses to determine its efficacy as an adjunctive treatment for laminitis pain and for treating neuropathic pain in cattle.

The mechanism of action of gabapentin (for its anticonvulsant, analgesic, or anxiolytic actions) is not fully understood. While gabapentin is structurally related to gamma-aminobutyric acid type A (GABA), it does not appear to alter GABA binding, reuptake, or degradation or to serve as a GABA agonist in vivo.4,5

In horses given single oral doses of 5 mg/kg, gabapentin was rapidly absorbed, with peak concentrations noted within 2 hours. Another study in horses showed that oral gabapentin had a low bioavailability (≈16%), and peak concentrations occurred ≈1 hour after administration. Elimination half-life was ≈7 to 8 hours, with gabapentin being cleared almost entirely by the kidneys.4

Gabapentin is considered contraindicated in animals that are hypersensitive to it. Since it is eliminated via renal routes, it should be used with caution in patients with renal insufficiency. Sedation and ataxia are the most likely adverse effects seen in small animals.4

Recently, preparations containing CBD oil have been suggested as adjuncts or substitutes for gabapentin in veterinary applications, but this remains controversial and probably requires further study.

NOTE: The Association of Racing Commissioners International Uniform Classification Guidelines for Foreign Substances has designated gabapentin a CLASS 4 DRUG.

Where to buy Gabapentin

Gabapentin is available in the U.S. through pharmaceutical manufacturers and through veterinary custom compounding companies. GABAPENTIN 300 MG/ML ORAL SUSPENSION, 1000ML by NexGen Pharmaceuticals is an excellent solution for complex partial seizures and nervousness in dogs and cats, for the treatment of chronic pain in many species and is an excellent adjunct to equine pain management regimens.

This product carries several potential drug interactions. Please consult your veterinarian prior to beginning any treatment regimen.

FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.

1van Weeren P.R., et. al. Disease in Aged Horses and Its Management. Vet Clin North Am Equine Pract. 2016 Aug;32(2):229-47. 

2Merck Veterinary Manual.

3rvc.ac.uk.

4Plumb’s Veterinary Drugs.

5Young J.M., et. al. Efficacy of orally administered gabapentin in horses with chronic thoracic limb lameness. Vet Anaesth Analg. 2020 Mar;47(2):259-266.