Amantadine for Dogs and Cats

Medically Reviewed by Kathleen Claussen, DVM on October 13, 2024
Written by Joshua Conrad, PharmD
4 min read

Amantadine (Symmetrel) is a medicine used in dogs and cats as a treatment for chronic pain, especially chronic nerve pain. It is usually added to other medicines for pain when those medicines are not working well enough. When used alone, amantadine does not provide much pain relief. Amantadine is classified as an N-methyl-D-aspartate (NMDA) receptor blocker.

All uses for amantadine in pets are considered to be “off-label” or “extra-label.” This means that there may be evidence of safe and effective use but the FDA has not approved that use.

There is no veterinary-specific formulation for dogs or cats. The human medicine, which can be used in animals, is available in oral capsules, tablets, and a liquid. All forms require a veterinary prescription and are available from human pharmacies. Contact your veterinary compounding pharmacy for alternative dosing options.

Amantadine is given by mouth as a tablet, capsule, or oral liquid. It is usually given once or twice a day.

Amantadine may be given with or without food. If stomach upset occurs, it may be given with a small amount of food or a treat. The oral liquid should be correctly measured using the supplied dosing dropper or syringe before giving. Slowly give liquid medications into a pet’s mouth so that they receive all of the dose.

It may take up to 10 days or longer to see the full effects of the medicine.

Always follow your veterinarian’s directions for giving medicines to animals. Remember to tell your veterinarian about any medicines, vitamins, supplements, or herbal therapies that you are giving your pet. Talk to your veterinarian before stopping any pet medicines.

  • Amantadine can be helpful when your pet is not getting enough pain relief from other medicines.

You and your veterinarian should monitor your pet for improvement of their condition as well as for side effects of the medicine. There are usually no routine blood tests that need to be performed.

Do not use amantadine in animals that are allergic to it. Safety in pregnant pets has not been established. Amantadine is found in breastmilk in humans taking the medicine. This is also likely to happen in dogs and cats, so caution is advised in nursing pets.

Studies with amantadine in dogs and cats are limited. Side effects that have been reported include:

  • Agitation (especially early in treatment in dogs)
  • Passing gas
  • Diarrhea or loose stools (especially early in treatment)
  • Difficulty with coordination and walking
  • Tiredness

Amantadine can also cause side effects associated with blocking a chemical in the body called acetylcholine. These side effects are common with many other medicines. They include constipation, dry mouth, dry eyes, blurry vision, difficulty peeing, and fast heart rate.

If you suspect that your pet is having a serious side effect or may have been overdosed, call your veterinary clinic immediately. If it is outside of regular office hours, you may contact a local emergency veterinary hospital or an animal poison control center. 

You can reach the ASPCA Animal Poison Control Center at 888-426-4435 or the Pet Poison Helpline at 855-764-7661.

Using multiple medicines can sometimes change how your pet’s medicines work or increase your pet’s risk for serious side effects. Always tell your veterinarian about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements that your pet is using.

In particular, make sure that you discuss if your pet is using any of the following before using amantadine.

Anticholinergic medicines. These medicines, including amantadine, block a chemical in the body called acetylcholine. They can cause constipation, dry mouth, dry eyes, blurry vision, difficulty peeing, and fast heart rate.  When used together, these can be even worse.

Medicines that change the pH of the urine. Some medicines may make the urine more or less acidic.  This can change how much amantadine your pet can eliminate.

This may not be a complete list of medicines that can interact with amantadine. Always check with your veterinarian.

  • Keep amantadine out of reach of children.
  • Wash your hands after giving amantadine to your pet.
  • Do not handle amantadine if you are allergic to it.

Amantadine should be protected from light and kept at room temperature. Do not store the oral liquid in the refrigerator or freezer. Compounded forms of amantadine should be stored according to the compounding pharmacy’s recommendations.