Gabapentin

Gabapentin is often used in dogs and cats to prevent seizures and treat neuropathic pain.

Mechanism of Action

Although gabapentin is a structural analog of the neurotransmitter gamma-aminobutyric acid (GABA), it appears not to interact with GABA receptors. 

• Its mechanism of action is not entirely clear but is likely related to inhibition of calcium and, possibly, sodium channels.¹

• Gabapentin is excreted unchanged in humans but is metabolized to N-methyl-gabapentin in dogs. 

  • Results in faster elimination and ability for shorter dose intervals in dogs as compared with humans²

• The metabolism of gabapentin has not been studied in cats, but pharmacokinetics demonstrates faster elimination than in humans, with similar implications for dose intervals as in dogs.³

Clinical Applications

Gabapentin has been used as an adjunct treatment for seizures in dogs and cats and as treatment for neuropathic pain.^4-9

• Gabapentin may be effective as an adjunct treatment for acute pain in humans (eg, pain following some surgeries, including spinal surgery and hysterectomy) and, to a lesser extent, in dogs and cats.^10-16 

  • However, meta-analyses of human studies have failed to show strong benefits.^17,18 

• A single case report described the successful use of gabapentin in the management of neuropathic pain in a horse.¹⁹ 

• Most evidence showing efficacy of gabapentin in pain management in animals is anecdotal and not based on controlled studies.

The recommended dose is variable, ranging from 10-20 mg/kg q8-12h in dogs^4,7-9,20 and 3-20 mg/kg q6-24h in cats.^7,14-16,20

• A dose of 2.5 mg/kg q12h has been used in a horse to treat neuropathic pain.¹⁹

Gabapentin has anecdotally been used in cats as a sedative to facilitate veterinary visits and procedures (eg, physical examination). 

• Doses of 50 mg/cat and 100 mg/cat have been shown to attenuate fear response in cats treated as part of a trap-neuter-return program.²¹

Adverse Effects

Sedation and ataxia are the most common adverse effects.^8,9,20

• Usually observed when doses at the higher end of the dose range are administered or when combined with other drugs that cause sedation

• May decrease after a few days of administration^9,20

Some liquid formulations of gabapentin contain xylitol, which is toxic in dogs; other formulations are xylitol free. 

• The xylitol-containing formulation may result in hypoglycemia in dogs when administered at the higher end of the dose range.

  • However, more severe toxicity (ie, liver failure) is unlikely unless extremely high doses (ie, >80 mg/kg) are used.²⁰