On P-chlorphenylalanine interference with phenobarbital formation from primidone.

Premedication with PCPA antagonized in rats the anticonvulsant activity of Primidone and of other drugs against seizures evoked by electroshock. Only in the case of Primidone, however, the anticonvulsant activity could not be re-established by increasing the dosage. Our investigations have shown that PCPA caused a strong inhibition of the conversion of Primidone to phenobarbital, both in vivo and in vitro.