Amantadine for Dogs: Uses, Side Effects, and Alternatives

Amantadine was initially formulated as an antiviral medication intended to treat influenza and combat infections. However, it’s also used off-label to treat chronic pain in dogs. In conjunction with other medications, such as non-steroidal anti-inflammatory drugs (NSAIDs), amantadine can help dogs struggling with nerve pain or degenerative joint disease to live comfortably.

While amantadine is one of many drugs both humans and dogs can take, you should only administer the drug when prescribed by a veterinarian. They can explain the dosage instructions and what side effects would necessitate discontinuing the medication.

How Does Amantadine Reduce Pain in Dogs?

Amantadine is also known under the brand names Symmetrel®, Gocovri®, Osmolex ER®, and Endantadine®. The drug was developed in the 1960s and later approved by the Food & Drug Administration (FDA). Amantadine belongs to a class of drugs called “adamantanes,” which are drugs designed to combat influenza A viruses. In veterinary medicine, amantadine comes as a tablet, syrup, and capsule.

Since its creation more than 60 years ago, amantadine has been used to address many health conditions in dogs, including severe osteoarthritis and certain types of cancer, such as osteosarcoma. Dr. Jerry Klein, the American Kennel Club’s Chief Veterinarian, explains how the drug works:

“Amantadine antagonizes (i.e. inhibits) N-methyl-D-aspartate (NMDA) receptors in the nervous system,” he says. “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.”

Because amantadine is absorbed through the dog’s gastrointestinal (GI) tract, it takes effect quickly. Most owners generally notice improvement within a week of the drug’s administration, although they may notice changes in a longer or shorter period, depending on their pet’s response to treatment.

What Is Amantadine Used for in Dogs?

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Alongside other medications, your veterinarian may prescribe amantadine if your dog suffers from:

• Osteoarthritis, a degenerative joint disease that affects mobility
• Cancer, particularly osteosarcoma
• Intervertebral disc disease (IVDD)
• Post-operative pain
• Chronic pain

As part of creating a well-balanced treatment plan, your veterinarian will consider many aspects of your dog’s health, including allergies and GI sensitivities. They’ll also evaluate whether your dog has any pre-existing health conditions that could cause serious side effects.

“The recommendations at this time are that amantadine should be used with caution in patients experiencing kidney disease, liver disease, congestive heart failure, and it should not be used in pregnant or lactating bitches,” Dr. Klein advises.

Veterinarians Generally Prescribe Amantadine With Other Drugs

Through its formulation and effect on the body, dogs prescribed amantadine can experience a remarkable change in their quality of life. It’s also a great option for dogs who cannot receive certain medications due to underlying medical issues. However, it’s not a miracle drug. To achieve the desired effect in dogs, it’s generally prescribed alongside other medications that target pain and discomfort.

“Studies have shown that overall, amantadine doesn’t tend to work very well on its own,” Dr. Klein explains. “But it does perform well in combination with other pain medications. For these reasons, veterinarians almost always use amantadine in combination with another pain medication, rather than use amantadine alone.”

A comprehensive treatment plan that involves amantadine use may also involve NSAIDs, gabapentin, and tramadol. Your veterinarian may also suggest some lifestyle changes that reduce joint pain and discomfort. For instance, adjusting an overweight dog’s diet can help them lose weight and reduce pressure on their joints. Feeding your dog food rich in protein and omega-3 fatty acids can also strengthen their musculoskeletal system and promote a fuller range of motion.

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Not All Drugs Work With Amantadine

When deciding whether to prescribe amantadine, your dog’s veterinarian will assess what other drugs they’re currently taking. That’s because, while amantadine works alongside many medications, some can cause negative interactions. These drugs include:

• Trimethoprim/sulfa antibiotics
• Thiazide diuretics used in treating hypertension
• Selegiline (Anipryl) used in canine cognitive disorder (CCD)
• Anticholinergic drugs (antihistamines), such as diphenhydramine (Benadryl)

Before giving any medication to your dog, discuss the decision with your veterinarian first. They can explain whether the drug contraindicates with amantadine and what other options you have for relieving your dog’s discomfort.

Side Effects of Amantadine for Dogs

Dr. Klein has some reassuring news for owners: amantadine is a fairly safe drug for dogs. Most patients adjust to the medication within a few weeks, and many of the common side effects subside without intervention.

Yet, some more serious side effects may warrant immediate veterinary care, such as seizures, agitation, and limb swelling. If you notice any of these signs, talk to your dog’s vet before administering amantadine again. They can explain whether amantadine is a good fit for your dog and alter their treatment plan as necessary.

Signs of Amantadine Overdose in Dogs

Don’t panic if you missed your dog’s amantadine dose. You can give the medication as soon as you remember, as long as it’s not within eight hours of the previous administration. Avoid double-dosing.

“[Amantadine] has a narrow therapeutic dose which is safe and effective, [and] only your veterinarian should be determining the dosage of amantadine for your dog’s particular situation and problem,” explains Dr. Klein.

By adhering to your veterinarian’s instructions, you can avoid an overdose. Signs and symptoms of poisoning in dogs include:

• Dilated pupils
• Tremors
• Disorientation
• Respiratory distress
• A fast, irregular heart rate
• Changes in blood pressure
• Aggression

“Signs of overdose … should warrant an owner to reach out to their veterinarian, a veterinary emergency service, or a pet poison hotline, such as the ASPCA Animal Poison Control Center or Pet Poison Helpline,” Dr. Klein says.