Amantadine for Dogs: Everything You Need To Know

If your vet has recently prescribed amantadine for dogs for your painful pup, you may have some questions about how this medication works, side effects to watch for, and its safety. Integrative veterinarian Dr. Julie Buzby is here to help with an in-depth review of amantadine—a great tool in the “pain management toolbox.”

Managing chronic pain in dogs may require a vet to think beyond the common pain medications such as NSAIDs, tramadol, and gabapentin. Perhaps the patient has an underlying condition that means an NSAID might not be safe or effective. Or in other situations it’s because those popular medications simply aren’t doing the trick anymore. In either case, sometimes the medication amantadine for dogs can be a huge help.

What is amantadine?

Better known by its brand name, Symmetrel®, amantadine hydrochloride is an antiviral medication that can also be used for the treatment of pain in dogs and cats. It antagonizes (i.e. inhibits) N-methyl-D-aspartate (NMDA) receptors in the nervous system. These receptors normally transmit pain signals. By temporarily inactivating the NMDA receptors, amantadine can prevent the pain signals generated in the body from reaching the brain. If the brain never gets the pain signal, it doesn’t perceive the pain.

Amantadine is especially helpful in cases of chronic pain, such as osteoarthritis in dogs. In these cases, repeated stimulation of pain pathways in the spinal cord and brain can cause harmful changes in the nervous system. The end result is that the nervous system becomes hypersensitive to painful stimuli.

This type of chronic pain stimulation can even lead to the nervous system interpreting non-painful stimuli (i.e. cold, light touch, or brushing) as painful. But the great news is that amantadine can help “reset” that sensitivity to more normal levels. 

Amantadine for dogs

The FDA has approved the use of amantadine in humans. Like many other medications labeled for humans, veterinarians used it “off-label” in dogs. This is nothing to be concerned about as off-label drug use is a fairly common occurrence in veterinary medicine. However, it is important to note that deciding which human medications are safe for use in dogs is best left to your veterinarian.

Many other human pain relievers are not safe for dogs. This is especially the case for over-the-counter NSAIDs (which is why the answer to “Can I Give My Dog Advil?” is a resounding “No!”). But amantadine passes the safety test. 

What is amantadine used for in dogs?

I tend to reach for amantadine in patients whose chronic pain has become worse over time without an obvious cause for the worsening. Often, that increased pain response indicates the dog’s nervous system has undergone changes making it abnormally sensitized to pain. In those situations, amantadine can prevent (and even reverse!) those changes, which improves pain management.

Veterinarians may prescribe amantadine to help decrease chronic pain and the related changes to the nervous system from:

• Arthritis
• Cancer such as osteosarcoma in dogs (bone cancer)
• Neurologic conditions such as disc disease (e.g. IVDD in dogs)

Since arthritis is so common in our beloved senior dogs, let’s take a closer look at how amantadine can help dogs who suffer from chronic pain associated with arthritis.

Amantadine in dogs and arthritis

Managing signs of arthritis in dogs is probably the most common application of amantadine in veterinary medicine. A study in the Journal of Veterinary Internal Medicine compared the effectiveness of a non-steroidal anti-inflammatory drug (NSAID) alone, with the combination of an NSAID and amantadine in dogs with arthritis.

The researchers found that dogs given both medications together engaged in significantly more physical activity. This suggests that the combination of amantadine and an NSAID was better for pain relief than using an NSAID alone.

Can amantadine be combined with other pain medications?

As you may have noticed, the study above looked at amantadine in combination with an NSAID, not by itself. Overall, amantadine doesn’t tend to work well on its own. But it does perform well in combination with other pain medications. For these reasons, vets almost always use amantadine plus another pain medication, rather than only amantadine.

Amantadine and NSAIDs

Amantadine is not known to have significant anti-inflammatory effects. However, arthritis has a large inflammatory component. Therefore, when treating arthritis, vets may choose to use amantadine in conjunction with non-steroidal anti-inflammatory drugs (NSAID) such as carprofen for dogs. The NSAID provides anti-inflammatory effects as well as pain control. And the amantadine boosts the level of pain relief.

However, vets may also choose to combine amantadine with other pain medications.

Amantadine and gabapentin

If you’re wondering “Can I give my dog gabapentin and amantadine together,” the answer is often “yes.” Both gabapentin for dogs and amantadine can potentially decrease the abnormally increased sensitivity of the nervous system that comes with chronic pain. But they do it in slightly different ways. This means combining amantadine and gabapentin may have a synergistic effect. However, it is best to speak with your vet about whether giving your dog gabapentin and amantadine together is the right choice.

Amantadine and tramadol

Additionally, you can give your dog tramadol and amantadine together too. Tramadol for dogs is a synthetic opioid that vets may use for pain control in dogs. The verdict is out on how well it controls pain by itself. But it does seem to work better in combination with other pain medications. This means that tramadol and amantadine can potentially be a useful combination. But again, your vet will decide what is right for your dog.

What is the amantadine dosage for dogs?

Your veterinarian will determine the best dosage of amantadine for your dog’s particular situation. Dogs can take it once or twice daily for treatment of chronic pain. Based on a study in Greyhounds, twice daily dosing is probably more effective than once daily dosing.

Common dosage forms include amantadine 100 mg tablets or capsules, 68.5 mg and 137 mg capsules, 129 mg and 193 mg tablets, and a 10 mg/ml liquid. Having the choice of tablets, capsules, and liquid gives several options for dogs who aren’t always cooperative for taking their medication. (As an aside, check out my article Your Dog Won’t Take Pills? for five helpful tips. Plus, the comments section below the article includes even more ideas.)

How long does it take for amantadine to work?

Amantadine is absorbed from the GI tract and starts to take effect fairly quickly in dogs. In one Greyhound study, peak blood levels occurred about one to four hours after oral administration.

Despite this, veterinarians usually recommend giving the amantadine for two to three weeks before deciding how well it is working. This is especially important if your vet prescribed amantadine for your dog for chronic pain. It can take some time for the nervous system changes (i.e. increased sensitivity to pain) to start responding to treatment.

Prior to starting the amantadine, it may be helpful to take a video of your dog walking or doing whatever actions seem to be painful. Also, you could write down some observations. Or you may want to rate your dog’s pain on a scale of 1 to 10 over several days. This gives you concrete data points to compare to how your dog is moving and acting after the two to three weeks of amantadine.

Sometimes, the improvement is remarkable and you don’t need those observations to notice it. However, having the ability to do a comparison can be a good way to notice more subtle changes in pain control.

Is amantadine safe for dogs?

Besides being a good option in our tool box for pain management, another plus is that amantadine is generally safe for most dogs. At this point, vets should use it with caution in patients with kidney disease in dogs, liver disease in dogs, congestive heart failure, or seizures in dogs. And it should not be used in pregnant or lactating dogs. These recommendations could change, however, once there are more studies characterizing its uses in dogs.

What are the side effects of amantadine in dogs?

While it is generally fairly safe, like most other medications, amantadine does also have some potential side effects for dogs.

Mild side effects of amantadine

When dogs first start taking amantadine, they more commonly experience mild side effects including:

Diarrhea

Some dogs may develop diarrhea in the first few days after starting amantadine. Thankfully, the loose stool is usually short-lived and resolves on its own. However, if you have any concerns, it is best to reach out to your vet.

Flatulence (i.e. increased intestinal gas)

You may notice that your dog has more gas (i.e. flatulence) than normal when he or she first starts taking amantadine. The good news, though, is that this usually improves after a few days.

Vomiting

Along with other signs of GI upset like diarrhea or flatulence, dogs may vomit when first taking amantadine. Often, giving the amantadine with food can solve this problem. But if it doesn’t, please consult your veterinarian.

Increased sleepiness

Your dog may want to lay around or sleep a bit more at first. And he or she may act like a lethargic dog. This increased sleepiness usually goes away in a few days though.

Less common but more concerning side effects of amantadine in dogs

Additionally, dogs may also experience some side effects that tend to be less common but more concerning.

Ataxia

Occasionally, you may notice that your dog is wobbly and off balance, having trouble navigating the stairs, or has an abnormal gait. These are all signs of ataxia. While ataxia can be a side effect of amantadine, it can also signal that the dog’s neurologic condition is worsening. So if you think your dog is ataxic, the best thing to do is give your vet a call.

Agitation or restlessness

While it doesn’t happen often, some dogs who take amantadine may become worked up, aggressive, or more restless than normal. If you notice any agitation, please stop giving the amantadine and contact your vet.

Dry mouth

Due to the anticholinergic effects of amantadine (i.e. blocking the “rest and digest” portion of the nervous system so that the “fight or flight” portion is dominant), some dogs may develop a dry mouth. Therefore, you may notice your dog keeps licking his or her lips or going to drink water more often.

Difficulty urinating

Because it has some action as an anticholinergic, amantadine can also cause urinary retention and difficulty urinating. If you see your dog straining to urinate, please call your vet. While it can be a side effect of the amantadine, difficulty urinating could also signal your dog has a UTI in dogs, bladder stones, or a urinary obstruction. Thus, it is important to get your vet involved.

Increased heart rate

The third potential anticholinergic side effect for amantadine is an increased heart rate. You may notice that your dog’s heart rate is elevated above baseline if your regularly check your dog’s vital signs. Or perhaps you might feel your dog’s heart beating faster than normal when you are snuggling.

Seizures

If your dog is already prone to seizures or is on a medication that lowers the seizure threshold, it is possible that amantadine could precipitate a seizure. That’s why it is so important that your vet knows your dog’s full medical history as well as all other medications and supplements your dog is taking.

Long term side effects of amantadine

At this point, there really isn’t enough data available about canine amantadine use to have a good idea of if dogs may experience adverse effects from using amantadine long-term. But it seems likely that the benefits amantadine can have for controlling chronic pain and improving quality of life would outweigh any potential risks of using it long-term.

Work with your vet

Often, dogs will adjust to the medication within a couple of weeks, and those adverse effects of amantadine will subside. If your veterinarian has prescribed amantadine for your dog, and you’re seeing side effects that concern you, please reach out to him or her. That way your vet knows what is going on and can help guide you on how to proceed.

What are the signs of an amantadine overdose in dogs?

If your dog receives an overdose of amantadine, you may notice signs such as tremors, dilated pupils, disorientation, coma, respiratory distress, heart arrythmias, changes in blood pressure, vomiting, or aggression.

Since amantadine has a relatively narrow therapeutic window (i.e. dose at which it is safe and effective), it is best to reach out to ASPCA Animal Poison Control Center, Pet Poison Helpline, or your veterinarian if your dog receives more than his or her prescribed dose of amantadine or if you have any concerns about a potential overdose. (There is a fee associated with calling the toxicology specialists, but the peace of mind is well worth it in my book.)

Are there any drug interactions with amantadine for dogs?

Overall, amantadine would get an “A” for getting along with other medications. There is a very short list of significant drug interactions with amantadine. And in most cases, the interaction is mild. These drugs that interact with amantadine include:

• Trimethoprim/sulfa—This antibiotic (often prescribed by vets for skin infections and urinary tract infections) can cause higher blood levels of amantadine. When using both medications together, the vet may need to adjust the dose of amantadine accordingly.
• Thiazide diuretics—Heart medications such as hydrochlorothiazide, which vets occasionally may use to treat high blood pressure (i.e. hypertension in dogs) or heart disease in dogs, can also raise blood levels of amantadine.
• Selegiline for dogs (Anipryl®)— This medication, which is sometimes recommended to treat canine cognitive dysfunction in dogs, can cause more stimulation or excitement when used with amantadine.
• Anticholinergic drugs—Antihistamines like Benadryl for dogs and other medications that have anticholinergic effects should be used with caution with amantadine. The combination of drugs could potentially increase the severity of the anticholinergic side effects (dry mouth, difficulty urinating, and increased heart rate).

Other than that, amantadine is not known to have significant drug interactions with other commonly used veterinary medications. This allows vets to feel confident prescribing it for patients they are also treating for other problems.

How Amantadine helped a senior dog

To add even more context to using amantadine for dogs, I wanted to share the story of one of my patients, Ella.

Usually, Ella, a 10-year-old Newfoundland with arthritis in her elbows and knees, loved to go for long walks in the woods with her mom. And for several years, she was still able to do that, thanks to daily gabapentin and an NSAID.

But as time went on, Ella’s mom noticed that her canine companion no longer wanted to go on her once-beloved walks. This was a clear sign to Ella’s mom that her dog’s current medications weren’t relieving the pain. So she brought Ella in to see me.

I performed an orthopedic exam on Ella. And I even repeated her X-rays to see if there were worsening arthritic changes in her joints. But I didn’t find anything that would explain why she was no longer comfortable on her current medications.

This made me suspect Ella’s chronic arthritis pain was causing nervous system changes that made her hypersensitive to pain. So I decided to try adding amantadine to her list of medications.

It took a few weeks to start seeing a difference. But soon enough Ella was jumping out of the car and leading the way down the trail again. She was overjoyed to be back in her favorite place, and her mom was thrilled to see her best friend feeling good again! 

Talk to your vet about amantadine for dogs

In the end, even though amantadine may not work as well as it did for Ella for every patient experiencing chronic pain, it can be a great tool in a veterinarian’s toolbox. It has great potential for keeping your furry friend active and enjoying life.

If you have questions about whether amantadine could be helpful for your pup or concerns about your dog who is currently taking amantadine, please don’t hesitate to talk to your vet. Even if your vet doesn’t think amantadine is the right solution for your dog’s situation, chances are he or she will be able to offer some other helpful pain management options.

Together, you and your vet can ensure your dog has the best quality of life possible. For some dogs, amantadine is exactly the solution they need to be able to hit the trail, fetch the ball, go for a swim, or do whatever it is that makes their tail wag.

Has your dog ever taken amantadine?

Please comment to share his or her story.