Primidone is available in Canada only by prescription.

Known as

Mysoline, Myidone, Apo-Primidone, Sertan


Primidone is prescribed, alone or in combination with other anti-epileptic medications to control simple partial, complex partial and tonic-clonic seizures.

How to Use

Take as prescribed. Primidone may be taken with food to prevent stomach upset.

Side Effects

Common reactions include muscular incoordination, dizziness, the sensation of the external world spinning (vertigo), headache, drowsiness, rash and nausea. These usually end after a period of being on the medication.


Avoid activities that require mental alertness until you and your doctor agree that your current dosage does not make you drowsy. Regular blood level checks must be done every six months. Older patients with kidney problems must also be monitored periodically. If you are pregnant or breastfeeding an infant, discuss with your doctor whether you should continue to take primidone.


Before beginning treatment, inform your doctor of all prescription and over-the-counter medication you are taking. Primidone may


the action of adrenocorticosteroids, phenytoin, tricyclic depressants, valproic acid and warfarin.

Missed Dose

Take next dose as soon as you remember. Do not double the dose. Resume your regular medication schedule.


Store at room temperature between 15°C and 30°C. Keep away from children, heat, light and moisture.


  • tablet: 250 mg, white, “AYERST” imprinted on one side
  • chewable tablets for children: 125 mg

Click here to learn more about medications.

DisclaimerExpand Disclaimer Section

The material offered at this site is to provide general information about epilepsy to the public. It is not intended to be taken as medical advice. Although all material presented at this site has been thoroughly researched and is believed to be correct, Epilepsy Ontario accepts no liability. Consult your physician and/or neurologist with any questions you have. People with epilepsy should never discontinue anti-epileptic medications or make changes in activities unless specifically advised to do so by an attending physician.