PRIMIDONE
(Mysoline)
Indication:
Primidone is useful in treating complex partial seizures.
Possible side effects: Primidone breaks down into primidone and
phenobarbital in the body. Consequently, one of the most common side effects is
drowsiness due to the phenobarbital. Hyperirritability is also common because
of the phenobarbital. At higher doses imbalance, dizziness, and double vision
may occur. This usually disappears with an adjustment in dose. Sexual impotence
and skin rash have also been reported. In rare instances individuals have reacted
to their first pill with extreme lethargy followed by insomnia.
You need to be aware that with any changes in your anticonvulsant therapy, there
may be an increase in seizure frequency. Keep in mind that side effects vary among
individuals. If you have any problem with medication, you should let your doctor
know, whether or not it is a problem listed above.
Dosage: The usual dose for the average adult is around 750 to
1000 mg/day. However, higher doses can be well tolerated for good seizure control.
Mysoline is supplied in 250 mg and 50 mg tablets. Suspension is also available.
Drug interactions: Acetazolamide and succinamide may decrease
primidone concentrations. Combining carbamazepine with primidone increases carbamazepine
levels with decreased primidone and phenobarbital levels. Isoniazid increases
primidone concentrations. Phenytoin stimulates conversion of primidone to phenobarbital.
Other drugs can affect or be affected by primidone.
Blood levels: The usual range for primidone is between 5 mcg/ml
and 15 mcg/ml and for phenobarbital is between 10 mcg/ml and 40 mcg/ml. Primidone
levels can be 20 mcg/ml or higher in patients taking only primidone. If you are
not having side effects and are still having seizures, your doctor may consider
using a dose which can result in higher blood levels.