Determination of phenobarbital by radioimmunoassay

A radioimmunoassay for phenobarbital has been studied. Antiphenobarbital antisera were obtained by repeated immunization of rabbits with p-succinamidophenobarbital conjugated to bovine serum albumin. Less than 0.2 pmol of phenobarbital could be measured by this procedure. The specificity of the antibodies was directed to substituents on the nitrogen atoms of the barbituric ring as well as to substituents at the carbon 5-position of the ring.