Key takeaways:
Amantadine is a prescription medication that treats chronic pain in dogs.
Amantadine is also an antiviral medication. But it’s rarely used for this purpose in dogs.
Dogs don’t usually have side effects from amantadine. They may occasionally have diarrhea and vomiting.
If your dog has osteoarthritis, cancer, disk disease, or another source of chronic pain, your veterinarian may prescribe amantadine (Symmetrel). The medication was first developed to treat influenza A in people, but today it’s commonly used to treat chronic pain in dogs.
Let’s review amantadine, including its uses, dosage, and potential side effects.
Common names | Amantadine (Symmetrel) |
What it treats | Chronic pain |
How it comes (forms) | Tablet, oral liquid |
Common side effects | Diarrhea, vomiting, gas, low appetite |
Average cost | $18-$55 (30 tablets) |
Amantadine (Symmetrel) was originally developed to treat viral infections in people caused by influenza A. However, scientists discovered that it also affected nerve function.
In dogs, it blocks a special pain receptor that can make pain feel worse if the animal is angry or anxious. Amantadine can also shut down the feeling of chronic pain in dogs when there should be no pain, like after a wound has completely healed.
In people, amantadine has evolved into a treatment for Parkinson’s disease.
Amantadine is not FDA approved for use in dogs, so veterinarians prescribe it off-label.
Veterinarians use amantadine to treat different types of pain in dogs. Chronic pain conditions that are commonly treated with amantadine include:
Cancer, such as osteosarcoma
Nerve pain from conditions like intervertebral disk disease
Amantadine typically works best as an add-on medication. So it’s often combined with other pain medications. Medications that are combined with amantadine to manage pain include:
Opioids, such as morphine
Your veterinarian will determine the best amantadine dosage for your dog based on several factors, including:
Your dog’s weight
The cause of your dog’s pain
The severity of your dog’s pain
Your dog’s overall health
Your dog’s other pain medications
You’ll typically give your dog amantadine once or twice daily, on a long-term basis. Follow your veterinarian’s directions carefully when giving amantadine. Giving too much may increase your dog’s risk of side effects.
Amantadine is a relatively safe medication for dogs. Most dogs do not have significant side effects from it. Any side effects are typically mild.
Gastrointestinal side effects of amantadine may include:
Giving amantadine with food may help prevent GI side effects. But contact your veterinarian if the side effects persist.
Some dogs become sleepy during the early days of amantadine treatment. Drowsiness often goes away as they get used to the medication. If your dog seems drowsy while taking amantadine, contact your veterinarian to determine the best course of action.
Rarely, dogs taking amantadine may experience serious side effects, including:
Restlessness
Incoordination
Difficulty walking
Limb swelling in dogs with heart conditions
If your dog reacts this way while taking amantadine, contact your veterinarian or an emergency veterinary hospital immediately.
Amantadine can be safely combined with a wide variety of medications. However, some medications do interact with it. These interactions may increase the risk of side effects or make amantadine less effective.
Drugs that may interact with amantadine include:
Antihistamines, such as diphenhydramine (Benadryl)
Atropine
Quinidine
Thiazide diuretics
Trimethoprim / sulfa (Bactrim)
Talk to your veterinarian about your dog’s medications. Tell them about any prescription medications, over-the-counter medications, and nutritional supplements. If your veterinarian knows your dog’s medications, they can help prevent the risk of drug interactions.
If you forget to give your dog a dose of amantadine, give the missed dose as soon as possible. If it’s almost time for your dog’s next dose, skip the missed dose and resume your dog’s regular dosing schedule. Do not give a double dose of amantadine.
Amantadine (Symmetrel) is a safe and effective treatment for canine pain. It is often combined with NSAIDs, opioids, and/or gabapentin to manage pain from arthritis, disk disease, or cancer.
Amantadine has a low risk of side effects, though some dogs may develop temporary tummy upset. Serious risks like seizures are possible. Talk to your veterinarian about whether amantadine may help your dog.
British Small Animal Veterinary Association. (2020). Amantadine.
Brooks, W. (2019). Osteosarcoma in dogs. Veterinary Partner.
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Chang, C., et al. (2023). Amantadine. StatPearls.
College of Veterinary Medicine. (n.d.). NSAID (non-steroidal anti-inflammatory drug) medication guide for animals.
Cornell Richard P. Riney Canine Health Center. (n.d.). Intervertebral disc disease.
Grubb, T. (2018). Gabapentin and amantadine for chronic pain: Is your dose right? Today’s Veterinary Practice.
Gruen, M. E., et al. (2022). 2022 AAHA pain management guidelines for dogs and cats. Journal of the American Animal Hospital Association.