What is gabapentin?
Approved by the FDA for humans, gabapentin (mostly known under the brand name Neurontin®) is a drug used to help with neuropathic pain and epileptic seizures. It is also commonly prescribed off-label to patients with anxiety disorders. Gabapentin has made a strong appearance in veterinary medicine in recent years, to treat the same conditions as it supposedly does in humans. The use of this drug is controversial, as the FDA has not approved it for veterinary use. Other brand names for this drug include (but are not limited to): Aclonium®, Equipax®, Gantin®, Gabarone®, Gralise®, Neurostil®, and Progresse®.
How does gabapentin work?
Gabapentin binds on the calcium channels in the cells. These channels are very important for brain functions and are upregulated (meaning their sensitivity is increased) in conditions such as anxiety, neuropathic pain, and epilepsy. The exact way that gabapentin affects the brain isn’t clear, but the current theory is that it blocks the calcium channels, which might suppress the overly stimulated neurons that are causing these conditions.
Gabapentin is mostly prescribed in combination with other medications, as an adjunctive therapy. It is taken through the mouth, and some forms of it contain xylitol, which is highly toxic to dogs. This is a drug that is quickly absorbed, so its effects are visible very rapidly. They don’t last very long (usually less than a day), as the drug is just as quickly eliminated. As a result, gabapentin needs constant administering to maintain its effects, which can be problematic due to the side effects.
What are the side effects?
The severity of the side effects depends on the dose, but they have been observed in some form in the majority of human and canine patients. The most frequently reported side effects of gabapentin are sedation and ataxia. Ataxia is the loss of motor control over the limbs, the main symptoms of it being weakened limbs (inability to walk, swaying, stumbling), drowsiness, tilting the head to one side, unresponsiveness, vertigo, and nausea. In December 2019, the FDA issued a warning about gabapentin having serious side effects on the human respiratory system. Patients have experienced breathing difficulty, disorientation, dizziness, unresponsiveness, and blue-colored skin.
In dogs, gabapentin is mainly metabolized by the liver and kidneys, which means frequent use can put extra stress on these organs. Dogs with pre-existing liver and kidney problems shouldn’t be prescribed high doses of gabapentin (if at all), and they may also experience stronger side effects. Dogs with epilepsy may suffer withdrawal seizures as a side effect of stopping the drug abruptly, so this is not recommended. They have to be taken off this medication gradually. The use of this drug can cause multiple nutrient deficiencies, such as calcium (therefore negatively impacting the health of bones), folate, and Vitamin D.
Notable Research on Gabapentin for Dogs
Chronic pain usually has a neuropathic cause, which is why regular pain medication doesn’t always help and why veterinarians prescribe gabapentin alongside it. There is a severe lack of research on how this drug affects dogs with neuropathic pain, so there is no optimistic scientific conclusion on this matter. Two notable studies researched the effects of gabapentin on post-operative pain. The first study, published in 2012, involved 63 dogs and found no significant effects of gabapentin on the pain. The researchers speculate that the dose might have been too low. The dogs also received pain relief medication before being given gabapentin, so this might have affected the results as well.
The second study was published in 2015, and it evaluated the effects of gabapentin on post-operative pain in twenty dogs, ten of which received gabapentin before the surgery (the other ten got placebo). In alignment with the 2012 study, the results showed once again that a commonly recommended dose of 10mg/kg twice a day did not affect the pain. But the results also showed that dogs who received gabapentin needed less pain medication (such as morphine) after the surgery in the first 24 hours. Gabapentin might have the potential of managing post-operative pain, but the right dosage and combination with other pain medications remain unclear. There is also no current evidence that gabapentin can help dogs in chronic pain.
A study of 17 dogs with epileptic seizures showed no significant decrease in seizures when gabapentin was added to their medical treatment. For some of the dogs, the time between the seizures did increase, and three of the dogs stopped having seizures altogether. Two of the dogs stayed seizure-free long-term, ten of them remained on gabapentin indefinitely. There were no visible long-term side effects. The short-term side effects were hind limb ataxia and sedation. They cleared up within days, or after adjusting the bromide dose (the drug that was given in combination with gabapentin). Dogs involved in this study received a higher dose of gabapentin, between 35 and 50 mg/kg per day, for four months.
Another study (done on mice) showed that gabapentin reduced acute seizures, but it was more effective in male mice. It’s important to note that the effects were only seen at very high doses, such as 200 mg/kg. There are currently no reliable, clinical, and detailed studies on gabapentin’s potential for treating canine epilepsy. The current conclusions show that gabapentin could help with epileptic seizures when paired with other medications, but the dose would have to be very high, and the responses may vary based on the sex.
Problematic Aspects of Gabapentin
The Question of the Dosage
With this drug, the dosage is thin ice. It determines whether or not the drug will have an effect, but there is absolutely no reliable information on what the appropriate starting dose is. Some say it’s 5mg/kg every 12 hours. Others put it at 10mg/kg every 8 hours. This creates a lot of uncertainty amongst veterinarians. If the dose is too low, the drug won’t show any effect, but if the dose is too high, the side effects become a problem. Since frequent dosing is needed to maintain the drug’s effect, the dose shouldn’t be left up to experimenting. Except, this is exactly the case.
There is no way to know how a dog will respond to a specific dose of gabapentin, so veterinarians need to rely on dog owners for feedback. Before the dose is determined, the desired result of the drug needs to be discussed between the owner and the vet. What is the endpoint? What are the signs that will let you know the medicine is working? Are you prepared for the side effects? Once the medication is prescribed, the dog should be monitored closely. If you’re noticing severe side effects and suspecting an overdose, contact your emergency veterinarian immediately!
The Lack of Reliable Research
There is an obvious lack of reliable and unbiased research on gabapentin for dogs. It’s not an easy drug to study. The drug is mostly prescribed in combination with other medications, so it’s hard to isolate its effects. Relying on human and mice studies isn’t a secure option either, as it has been proven that dogs metabolize gabapentin differently.
Assuming that the dosage (or the efficiency) of the drug that was established in human studies could easily be applied to dogs is troubling and risky. The few canine studies that do exist are too small, inconclusive, or have questionable reliability – for example, they are done in retrospect and rely on the owners to evaluate and report the symptoms, or they are otherwise biased.
Unregulated Status of Gabapentin
Gabapentin is not FDA-approved for veterinary use. There is no regulation for this drug when it comes to administering it to dogs. Some veterinarians are prescribing gabapentin precisely because of the side effects, such as sedation. Dogs are given gabapentin before a stressful situation, such as traveling or a vet visit. The owners don’t realize that the sedation is actually a side effect of a strong drug that is normally given to epileptic patients.
As mentioned several times throughout this article, the appropriate dose (which is the most critical aspect of any medication) remains a complete mystery and is entirely up to each veterinarian to decide on their own, aside from some general guidelines that were lifted from human studies. The use of this drug is experimental at best and can (in most cases) be classified as a questionable choice.
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Luna’s passion for learning about canine psychology and behavior began when she adopted a severely reactive puppy from a local shelter. She is now a big advocate for positive reinforcement and compassionate training. As a writer, she strives to spotlight the topics that fly under the radar and be the voice for all who cannot speak for themselves.