THE METABOLIC CONVERSION OF PRIMIDONE (MYSOLINE®) TO PHENOBARBITONE IN PATIENTS UNDER LONG-TERM TREATMENT

Abstract

The serum phenobarbitone concentrations were measured in 47 patients who were under treatment with primidone for more than 1 year, and compared with the readings obtained from 41 patients treated with phenobarbitone. The % of primidone converted to phenobarbitone in the organism was calculated as an average of 24.5%. Randomly selected primidone-treated patients had on the average a serum phenobarbitone content of 35 mg/1. This was of the same order of magnitude as found in randomly selected patients treated with phenobarbitone (30 mg/1). In 19 adult patients (9 men and 10 women) who suffer from epilepsy, and who were under treatment with primidone for more than 1 year, primidone was replaced by phenobarbitone, the serum phenobarbitone concentrations being maintained constant and equal to the concentrations obtained during the preceding treatment. During the trial, which extended over a period of 6-8 months, comparisons were made between both the eeg and the clinical state before and after the exchange of drugs. Neither eeg nor clinical investigation showed any tendency to a change in the state of the patients. There Is doubt as to the independent anticonvulsant effect of primidone.