General Information: Mysoline is an older anticonvulsant drug. Mysoline is used to treat grand mal, complex partial (psychomotor) and focal seizures. Sometimes children who don't tolerate Phenobarbital will tolerate Mysoline better.

Formulations: Mysoline is available in the following formulations:

• 50 mg tablet (scored)
• 250 mg tablet (scored)
• A scored tablet may be cut in half
• 250 mg/5 ml liquid suspension

Dosage: The usual dosage of Mysoline is 8 - 20 mg/kilogram of body weight per day up to a maximum dose of 2 gm per day. Usually treatment is started at 1/3 or 1/4 of the calculated dose appropriate for the patient and gradually increased to the full amount within 3 weeks. Slowly increasing this drug often avoids unpleasant side effect such as dizziness or drowsiness. Mysoline is usually taken two or three times a day.

Therapeutic Drug Levels: Once Mysoline is taken, it is partly converted in the body to Phenobarbital. Because it is partly converted to Phenobarbital, both Primidone and Phenobarbital levels are checked. The blood level of Primidone that is found to prevent seizures in most people is between 4-10µg/ml.

Side Effects: All drugs have side effects. The most common side effects of Mysoline are sedation, dizziness, and incoordination. These effects tend to disappear with continued therapy or with a reduced dose. Occasionally, nausea, decreased appetite, vomiting, fatigue, hyperirritability, hyperactivity or a rash has been reported. An occasional child will have a severe, but temporary reaction after the very first dose of Mysoline. This is usually in the form of dizziness or abnormal behavior and often requires discontinuation of the drug. Lowering of the blood count has been reported rarely.

Toxic symptoms are symptoms experienced when the blood Mysoline level is too high. Toxic symptoms can include excessive drowsiness, staggering or slurred speech.

Common Labs: Scheduled monitoring of blood cell counts and Mysoline levels have increased the safety and efficacy of Mysoline. We will usually recommend a Mysoline level 4 weeks after reaching a therapeutic dose, and every 4-12 months thereafter. We will also recommend checking a complete blood count (CBC) every 4-12 months.

Drug Interactions: Concurrent use of Mysoline and alcohol may result in excessive central nervous system depression. Because Mysoline is partly converted to Phenobarbital, it will have the same drug interactions as Phenobarbital. Phenobarbital does affect the metabolism or absorption of several medications. Your local pharmacist can often tell you if there are any known drug interactions between Phenobarbital and medications your child is taking.

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