Gabapentin in dogs and cats: does it really work?

By: Bruna Sarri, Jaqueline Pizzaia e Adriano Carregaro

Gabapentin is an anticonvulsant drug, structurally similar to GABA, that is gaining ground as adjuvant analgesic, especially in the treatment of chronic and neuropathic pain in small animals. Despite its proven efficacy in pain control in human medicine, its use is still widely questioned in veterinary medicine. However, we can already see recommendations for gabapentin as an adjuvant analgesic in various sources, such as this one from the International Veterinary Academy of Pain Management (IVAPM).

When should gabapentin be used?

The main use of gabapentin is as an anticonvulsant in cases refractory to other medications, or as an adjunct to other anticonvulsants such as phenobarbital and potassium bromide. However, its analgesic function, or rather analgesic adjuvant, has been gaining more and more prominence in the treatment of pain in animals.

As an analgesic, this drug has been useful in treating animals suffering from chronic neuropathic pain resulting from accidental or surgical trauma, limb amputations, spinal cord injuries, intervertebral disc herniation, tumors in the central nervous system, pelvic fractures, erroneous incorporation of nerve tissue into sutures, inguinal hernias, syringomyelia, among others.

A study found that gabapentin was effective in reducing signs of neuropathic pain in guinea pigs, such as hyperalgesia and allodynia. In rats, gabapentin administered orally and subdually inhibited the transmission of inflammatory pain and reduced hyperalgesia generated by peripheral nerve injuries and burns.

Apparently, gabapentin was able to reduce the need for morphine in the postoperative analgesia of female dogs undergoing mastectomy, but it did not eliminate the need for this opioid. In cats, long-term treatment with gabapentin has been found to be beneficial in controlling pain derived cranioencephalic trauma and musculoskeletal diseases.

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In what situations might it not work?

A study conducted with dogs undergoing anterior limb amputation concluded that the use of gabapentin as an analgesic adjunct, both perioperatively and postoperatively, did not provide postoperative analgesic benefit compared to animals that did not receive this adjunct.

Another study with dogs undergoing intervertebral disc surgery also did not observe a reduction in pain in dogs receiving gabapentin compared to those receiving opioid analgesia. However, a trend of lower pain scores was detected in the group that received gabapentin supplementation. This may be due to the fact that acute postoperative pain is considered nociceptive, and gabapentin has an anti-hyperalgesic effect but not an antinociceptive effect.

Does Gabapentin has side effects?

Despite gabapentin gaining popularity in pain treatment, we must remember that it can trigger some unwanted effects. Therefore, it should be used with caution and always under the guidance of a veterinarian.

In humans, clinical trials with chronic administration of gabapentin found side effects in 25% of patients, including fatigue, drowsiness, and weight gain. However, all effects ceased upon discontinuation of the medication. In small animals, studies indicate similar effects, with sedation being the most common, followed by ataxia, nystagmus, lack of appetite, fatigue, weight gain, vomiting, and drooling. Therefore, it is always important to assess the benefits of using gabapentin and the potential side effects on a case-by-case basis.

Gabapentin as sedative?

Besides the discussions generated regarding the deleterious effects of its long-term use, there are also controversies regarding its use as a sedative for transporting cats, which has become equally popular in veterinary clinics.

Studies indicate that doses above 20 mg (between 50 mg and 100 mg) reduce aggression and stress in cats during handling, provided they are administered 2 to 3 hours beforehand. However, in one of those studies, it was found that the 100 mg dose caused sedation (80%), ataxia (40%), hypersalivation (6.7%), and vomiting (13.3%), effects that can lead to the cat's lack of appetite for up to a day, increasing the chances of developing hepatic lipidosis. Perhaps it's not the best option to calm the cat during transportation...

So...

Given this information, we realize that gabapentin can be a good alternative as an adjuvant for treating patients with neuropathic or chronic pain, especially those who do not respond well to conventional analgesics. However, frequent clinical monitoring of treated patients is necessary to monitor undesirable effects so they do not outweigh the benefits. Additionally, animals treated for extended periods should undergo regular biochemical evaluation to prevent liver and kidney overload, especially in cats predisposed to developing chronic kidney disease.

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Find out more:
– Adrian et al. The pharmacokinetics of gabapentin in cats. J Vet Int Med, 32:1996-2002, 2018.
– Aghighi et al. Assessment of the effects of adjunctive gabapentin on postoperative pain after intervertebral disc surgery in dogs. Vet Anaesth Analg, 39:636-646, 2012.
– Crociolli et al. Gabapentin as an adjuvant for postoperative pain management in dogs undergoing mastectomy. J Vet Med Sci, 77:1011-1015, 2015.
– Fox et al. Comparative activity of the anti-convulsants oxcarbazepine, carbamazepine, lamotrigine and gabapentin in a model of neuropathic pain in the rat and guinea-pig. Pain, 105:355-362, 2003.
– Jones DL; Sorkin LS. Systemic gabapentin and S (+)-3-isobutyl-γ-aminobutyric acid block secondary hyperalgesia. Brain Res, 810:93-99, 1998.
– Lorenz et al. Long-term use of gabapentin for musculoskeletal disease and trauma in three cats. J Fel Med Sur, 15:507-512, 2013.
– Mao J, Chen L. Gabapentin in pain management. Anesth Analg, 91:680-687, 2000.
– Pankratz et al. Use of single-dose oral gabapentin to attenuate fear responses in cage-trap confined community cats: a double-blind, placebo-controlled field trial. J Fel Med Surg, 20:535-543, 2018.
– Ruel HLM; Steagall PV. Adjuvant analgesics in acute pain management. Vet Clin: Small An Pract, 49:1127-1141, 2019.
– Van Haaften et al. Effects of a single preappointment dose of gabapentin on signs of stress in cats during transportation and veterinary examination. J Am Vet Med Assoc, 251:1175-1181, 2017.
– Wagner et al. Clinical evaluation of perioperative administration of gabapentin as an adjunct for postoperative analgesia in dogs undergoing amputation of a forelimb. J Am Vet Med Assoc, v. 236, n. 7, p. 751-756, 2010.