Pharmacokinetics of Phenylethylmalonamide (PEMA) in Normal Subjects and in Patients Treated with Antiepileptic Drugs

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Abstract
The pharmacokinetics of phenylethylmalonamide (PEMA), a major metabolite of primidone, was investigated following administration of single oral doses (400 mg) to 6 normal subjects and 6 patients receiving chronic treatment with antiepileptic drugs. Peak serum PEMA levels were usually attained within 2-4 h after intake. The oral bioavailability estimated on the basis of the recovery of unchanged drug in the urine of normal subjects was at least 80%. Half-life values ranged from 17-25 h in normal subjects and from 10-23 h in the patients. No statistically significant difference in any of the calculated kinetic parameters could be found between the 2 groups. The data indicate that PEMA is readily absorbed from the gastrointestinal tract and that it is eliminated predominantly unchanged in the urine of man.