primidone, Mysoline (cont.)

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Suddenly stopping medications for seizures may cause seizures.

PREPARATIONS: Tablets: 50 and 250 mg

DRUG INTERACTIONS: Primidone may decrease blood levels and the effect of several drugs by increasing the activity of liver enzymes that breakdown these drugs. Examples of drugs affected by Primidone include naloxegol (Movantik), roflumilast (Daliresp), lurasidone (Latuda), and many others.

PREGNANCY AND BREASTFEEDING SAFETY: Primidone has not been adequately evaluated in pregnant women. Some other seizure medications have been associated with birth defects.  Primidone is excreted in human milk and may cause adverse effects in the infant.

STORAGE: Primidone should be stored at room temperature, 20 C - 25 C (68 F - 77 F).


  • Patients 8 years of age or older should be treated with the following regimen:
  • Days 1 to 3: 100 to 125 mg at bedtime.
  • Days 4 to 6: 100 to 125 mg twice daily.
  • Days 7 to 9: 100 to 125 mg three times daily.
  • Day 10 to maintenance: 250 mg three or four times daily.
  • The maximum dose is 2 g daily.
  • It takes several weeks before the antiseizure effects of primidone are seen.

DRUG CLASS AND MECHANISM: Primidone is an oral anticonvulsant (anti-seizure) medication used for treating several types of seizures. Its exact mechanism of action is not known. Primidone is converted into phenobarbital and phenylethylmalonamide (PEMA) in the body. Primidone, phenobarbital, and PEMA all have anticonvulsant activity. In addition to its anticonvulsant activity, PEMA increases the anticonvulsant activity of phenobarbital. The FDA approved primidone in March, 1954.

Reference: FDA Prescribing Information

Medically Reviewed by a Doctor on 1/21/2016

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