Mysoline (primidone) is not used very often but it can be effective. Mysoline is broken down in the body into PEMA and phenobarbital, both of which are effective antiseizure compounds. Therefore, taking Mysoline gives you the effectiveness of phenobarbital plus additional protection. A patient whose seizures have not been controlled by phenobarbital may have better results from Mysoline.

The most important study of Mysoline (primidone) looked at 622 adults who had partial seizures or secondarily generalized tonic-clonic seizures. Each person was treated with one of four medications. The four were primidone, phenobarbital, carbamazepine (Tegretol or Carbatrol), and phenytoin (Dilantin, Phenytek). Overall, the patients who took primidone were more likely to stop taking it because of intolerable side effects than those who took the other medicines. After the first month, however, there was hardly any difference in this regard between the primidone and the carbamazepine or phenytoin.

The patients in this study who had tonic-clonic seizures achieved similar control from all four medications. Of those in this group who took primidone for a year, 63% were seizure-free. Patients were more likely to continue to take carbamazepine (Tegretol, Carbatrol) than the other medications when considering both seizure control and side effects, but Mysoline can be very effective for partial seizures.

A similar study in children—which also included Depakote (valproate)—focused on the rate of side effects. Only 8% of the children who were given Mysoline had to stop taking it because of side effects. Phenobarbital, which can be an excellent medication, often is avoided in children because of the possibility of mental slowing. By using Mysoline alone, children can enjoy many of the same benefits while avoiding this problem because the amount of phenobarbital produced by breaking down the Mysoline is low.

Mysoline is most often used as adjunctive (add-on) therapy in adults whose seizures are not well controlled by other medications. It is frequently paired with carbamazepine (Tegretol or Carbatrol) or phenytoin (Dilantin, Phenytek), but no single combination of antiepileptic medications is perfect for everyone. Sometimes, a series of combinations must be tried before finding what is best for the individual patient.

See more information about the studies discussed here.

Reviewed February 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.