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Gabapentin for Chronic Pain in Pets

For Veterinary Practices
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For Pet & Horse Owners
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By Evan Ware, DVM

Overview

Therapeutic Class
Gamma-aminobutyric Acid (GABA) analog

Species
Dogs, cats and horses (foals)

May Be Prescribed by Vets for:
Idiopathic epilepsy, pain management, seizures due to neonatal hypoxia.

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Basic Information

Gabapentin is an anticonvulsant prescribed by veterinarians predominantly to treat chronic pain in dogs, cats, and other animals. It also is used as a seizure-control agent, either by itself or in conjunction with other anti-seizure medications. Dosage can vary widely.

Gabapentin is a structural analogue of GABA, an inhibitory neurotransmitter. The mechanism of action of Gabapentin is not well understood, although it does not affect GABA binding or reuptake, or behave as a GABA agonist. Gabapentin is used in human medicine to treat seizures and many types of pain, including neuropathic pain, diabetic neuropathy, malignant pain, central pain, complex regional pain, and trigeminal neuralgia.

Veterinary Medicine Uses for Gabapentin

Gabapentin is used in both dogs and cats to treat chronic pain, particularly of neuropathic origin. It appears to be most effective when combined with other types of analgesic agents, for example NSAIDs, allowing prescribing lower doses. It has been shown to be an appropriate treatment for reducing hyperalgesia and allodynia associated with neuropathic pain. It also is used in chronic arthritic pain and pain associated with malignancy.

Gabapentin is used as an adjunctive therapy for dogs and cats with refractory idiopathic epilepsy. There are conflicting clinical reports about its efficacy when used for this purpose, although some studies report improvement in as many as 50% of dogs studied.

In dogs, oral Gabapentin is well absorbed in the duodenum, with peak levels occurring approximately one to two hours after administration. It is partially metabolized by the liver and excreted by the kidneys. Gabapentin has a short half-life of between two to four hours. No pharmacokinetic information about uptake and metabolism was found for cats.

In horses, Gabapentin can be used to control seizures in foals suffering from hypoxic ischemic encephalopathy.

Potential Side-Effects of Gabapentin

The most-common side effects attributed to Gabapentin include mild sedation, ataxia, and occasional diarrhea. Sedation can be minimized by tapering from a smaller starting dose to the desired dose. When treating seizures, it is ideal to wean off the drug to reduce the risk of withdrawal seizures. This drug also can cause a false positive reading on urinary protein tests.

Drug Interactions with Gabapentin

Gabapentin is commonly found to be more effective for pain management at the beginning of treatment when administered alongside another pain reliever like hydrocodone or morphine. After a period, the second narcotic can be dropped from the therapy and Gabapentin will remain the sole pain reliever.

Gabapentin should not be administered within two hours of oral antacids or the antacids will hinder absorption of the Gabapentin, making it less effective.

Precautions for Using Gabapentin

Gabapentin should not be prescribed to patients with a known allergy or hypersensitivity to the drug. It also is not recommended for use in pregnant animals.

If the patient has been on Gabapentin treatment for a while, abrupt cessation of the drug is not recommended, as seizures can occur. Instead, the patient should be gradually weaned off the medication over a period of about two weeks.

Use extreme caution when prescribing this medication to a patient with kidney problems, as Gabapentin is removed from the body through the kidneys.

The human oral-solution of Gabapentin contains xylitol, which should be avoided in veterinary patients.

Gabapentin should be used with caution in animals with decreased liver or renal function.

Gabapentin should not be stopped abruptly because withdrawal can precipitate seizures or rebound pain. The dosage should be decreased over the course of two to three weeks.

In laboratory animals, Gabapentin was associated with fetal loss and teratogenic effects. It also is present in milk. It should be used during pregnancy or lactation only when the benefits outweigh the potential risks.

Dosage and Administration of Gabapentin

Compounded Gabapentin is available in either an oral or topical formulation. The veterinarian determines dosage, mode of administration, and frequency of administration according to the condition being treated and the individual needs of the patient.

For very small unique, weight-based doses, like that required to treat a cat or other small animal, a veterinary compounding pharmacy can facilitate the formulation.

Overdose would likely cause increased severity of side effects including lethargy, somnolence, depression, and ataxia. If recognized promptly, gut-emptying protocols including emesis, activated charcoal, and cathartics can be helpful.

About the Author

Dr. Evan Ware

Dr. Evan Ware is a veterinary practitioner in Phoenix, Arizona. He received both his undergraduate degree in microbiology and his Doctorate of Veterinary Medicine from The Ohio State University.

Dr. Ware is currently the Medical Director of University Animal Hospital (VCA) and is also the owner of two other hospitals, including Laveen Veterinary Center and Phoenix Veterinary Center. His areas of expertise include orthopedic medicine and surgery, veterinary oncology and chemotherapy, and general and advanced soft-tissue surgery.