Amantadine is an FDA-approved medication for people. But veterinarians often prescribe it off-label to treat chronic pain in cats and dogs. It’s an NMDA antagonist that works to block pain signals in pets. Amantadine comes as tablets, capsules, and a commercially-available liquid. Pets usually need to take the medication by mouth once or twice a day. Side effects for cats and dogs include gas and diarrhea. Amantadine is typically given with other pain medications.
Amantadine is an N-methyl-D-aspartate (NMDA) antagonist. It works by blocking the NMDA receptor. This helps stop nerves from sending pain signals to the brain, which reduces the feeling of pain.
The following side effects might get better over time as your pet gets used to the medication. Let your veterinarian know immediately if your pet continues to experience these symptoms or if they worsen over time.
Contact your veterinarian immediately if your pet experiences any of the following.
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
More common
Bladder pain
bloody or cloudy urine
blurred vision
confusion
difficult, burning, or painful urination
dizziness or lightheadedness
fainting
falls
frequent urge to urinate
lower back or side pain
seeing, hearing, or feeling things that are not there
swelling of the hands, feet, or lower legs
Less common
Inability to move the eyes
increased blinking or spasms of the eyelid
sticking out of the tongue
trouble breathing, speaking, or swallowing
uncontrolled twisting movements of the neck, trunk, arms, or legs
unusual facial expressions
Rare
Chills
decreased vision or any change in vision
difficulty in coordination
increased blood pressure
increase in body movements
irritation and swelling of the eye
loss of memory
mental depression
seizures
severe mood or mental changes
skin rash
slurred speech
thoughts of suicide or attempts at suicide
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
More common
Agitation
difficulty concentrating
headache
irritability
loss of appetite
nervousness
nightmares
purplish red, net-like, or blotchy spots on the skin
trouble with sleeping
Less common
Blindness
blurred vision
decrease in sexual desire
decreased vision
drowsiness
dryness of the mouth, nose, and throat
false sense of well-being
joint swelling
unusual tiredness or weakness
vomiting
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
Tips for the liquid form of amantadine for cats and dogs:
Amantadine can cause some serious health issues. This risk might be even higher for certain pets. If this worries you, talk to your veterinarian about other options.
If your cat or dog takes too much of amantadine, even by a little, it can lead to a dangerous overdose. This can happen if you accidentally give your pet too much medication.
An amantadine overdose can also happen if you give the medication to a cat or dog with kidney problems. When the kidneys don’t work properly, the body can’t get rid of amantadine. This can lead to too much medication in the body. Talk to your vet before giving this medication to your pet if they have kidney problems.
Signs of an amantadine overdose in pets include vomiting, restlessness, and seizure. Call a vet or a pet poison helpline right away if you think your pet has taken too much amantadine.
Amantadine might make the body hold onto extra fluid, which can cause swelling in your pet’s legs. The risk of complications from this fluid buildup is higher if your cat or dog has heart or kidney problems.
Tell your vet if your pet has any heart or kidney issues to make sure amantadine is safe. Call your vet if you notice that your pet’s legs swell after they start taking the medication.
Some cats and dogs might act differently while they’re taking amantadine. They might seem anxious, nervous, aggressive, restless, or want more attention than usual. Talk to your vet if your pet’s behavior changes in a way that worries you.
Talk to your vet before giving amantadine if your pet has liver problems. Cats and dogs with a liver condition should take this medication with caution. We don’t know whether amantadine is safe for pets with liver problems. But in people, this medication has a rare risk of raising liver enzyme levels, which can be a sign of liver damage.
Your pet’s amantadine dose will be based on their weight. The typical dose for cats and dogs is 3 mg/kg to 5 mg/kg by mouth every 12 or 24 hours.
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.
Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Contraindications are specific health conditions or situations in which a pet should not take a medication due to safety concerns. If your pet has any of the following conditions or if any of the following apply to your pet, let your veterinarian know because Amantadine will not be safe for your pet to take.
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