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Product Description

Comprehensive Guide to Primidone

Meet the Pet Epilepsy Controller: Primidone!

Primidone is a prescription-only anticonvulsant pill or tablet that reduces the frequency and severity of seizures associated with epilepsy. The medication is used in both dogs and rarely in cats. Primidone is an oral tablet that is administered every 8 to 12 hours. Primidone is an anticonvulsant medication used to help prevent dogs or cats with epilepsy from experiencing seizures. This drug makes it more difficult for one's nervous system to fire off uncontrollably, which is one of the main causes of a seizure. Also used to help speed up the detoxification of chlorinated hydrocarbons insecticide poisoning, Primidone has a number of different applications. While the actual mechanism behind which this drug works is still not fully understood (many drugs working on our neural pathways are this way), we do know that it is incredibly effective as an anti-seizure drug.

How does Primidone work?

Primidone is the generic alternative for brands Neurosyn, Mylepsin, and Mysoline. This medication's ingredients are Primidone 250 mg.

Primidone's mechanism of action is as an anticonvulsant that treats seizure disorders, including infectious neuropathies such as virus encephalitis and canine distemper. Once ingested, Primidone is converted to anticonvulsant phenobarbital and reduces seizures by decreasing nerve impulses in the CNS (central nervous system).

How is Primidone administered?

Primidone is a 250 mg tablet that is administered orally every 8 to 12 hours. The recommended usual dosage in dogs is 2.3 to 6.8 mg per pound of the pet's body weight. Allow plenty of water for your pet to drink.

What are the precautions or warnings of which you should be aware?

The following pets cannot be prescribed Primidone medication.

  • Those with liver disease

  • Those that are pregnant or lactating

  • Those who are taking steroids or anesthetics

  • Those that are taking theophylline (i.e., bronchodilator) or digoxin (i.e., antiarrhythmic)

What are the potential Primidone side effects of which you should be aware?

Primidone can cause an increase in liver enzymes, changes in eating or drinking, behavioral changes, sedation, or jaundice. Severe side effects are dizziness, poor coordination, or drowsiness, blurred vision, nausea, or vomiting.

Immediately, consult a veterinarian or emergency clinic if any above side effects or any allergic reactions occur.

Frequently asked Questions
  1. What is Primidone, and what is it used for?

    Primidone is used in the treatment of seizure disorders associated with epilepsy and belongs to the drug class barbiturate anticonvulsants.

  2. Is Primidone a controlled substance?

    Primidone 250 mg is not a controlled substance under the Controlled Substances Act.

  3. What is the usual Primidone dosage?

    The usual Primidone dosage is 2.3 to 6.8 mg per pound of the pet's body weight.

  4. What are the Primidone brand names?

    Neurosyn, Mylepsin, and Mysoline.

  5. What is the Primidone drug class?

    Primidone is part of the drug class Barbiturate, which are anti-anxiety, sleep-inducing, and anticonvulsant drugs.

Concluding Thoughts

The most important thing that you should know about Primidone is that the medication cares for pets with unfortunate seizure disorders associated with epilepsy by reducing the frequency and severity of seizures. The tablets treat seizure disorders by decreasing nerve impulses in and from the central nervous system in pets.

DISCLAIMER:FDA law restricts Primidone only on order or prescription of a licensed veterinarian for the best pet health care advice. Ask your veterinarian or consult with one of our pet care specialists at 1-800-844-1427, if this is a suitable product for your pet and your home. This informative article is not meant to substitute for the diagnosis, treatment, and professional advice from your veterinarian or other qualified professionals regarding a medical condition. Never disregard or delay seeking professional advice due to what you may have read on our website. Our medications are FDA-approved and/or EPA regulated when and as required by law.

Side Effects & Warnings

If your pet develops any of the following serious side effects, stop giving primidone and seek emergency veterinary medical attention; an allergic reaction (difficulty breathing, closing of the throat, swelling of the lips, tongue, face, or hives); a rash; worsening of seizures; fever. Other less serious side effects may occur. Continue to give primidone and talk to your veterinarian if your pet experiences dizziness, poor coordination, or drowsiness; blurred vision; irregular back and forth movements of the eyes; or nausea and vomiting

Possible interactions: Acetazolamide (Diamox), carbamazepine (Tegretol), ethosuximide (Zarontin), and methsuximide (Celontin) may decrease the effects of primidone and require a higher primidone dose. Phenytoin (Dilantin), ethotoin (Peganone), mephenytoin (Mesantoin), and isoniazid may increase the effects of primidone and require a lower primidone dose. Carbamazepine (Tegretol) blood levels may increase when given primidone. The carbamazepine dose may need to be adjusted lower. CNS depressants, valproic acid, and chloramphenicol may increase the effect of primidone. Primidone may decrease the effect of coumadin, corticosteroids (such as prednisone), beta-blockers (such as atenolol), theophylline, and metronidazole. Use caution when giving primidone with furosemide, griseofulvin, or rifampin.

Primidone should be taken with caution in patients with hypovolemia, anemia, hypoadrenocorticism, and kidney disease. Not to be given to patients with severe respiratory dysfunction, liver disease, or pets with a known sensitivity to drugs of this class. This drug's use in cats should be carefully monitored due to respiratory depression. Primidone might decrease the effects of oral anticoagulants, beta-blockers, corticosteroids, estrogen agents, progestins, and tricyclic antidepressants, while drugs like phenothiazine opiate agonists, CNS depressants, and antihistamines might increase the effects of Primidone. 

Keep out of the reach of children and other pets.


Primidone 250mg


Use as directed by your veterinarian.

Dogs (all weights) The usual dose in dogs is 2.3-6.8 mg per pound of pet’s body weight per day in 2 or 3 divided doses. Primidone can be given with food. Allow plenty of water for your pet to drink.

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