Separatory determination of pentazocine enantiomers in plasma by radioimmunoassay using specific antisera

A method for separatory determination of d- and l-pentazocine in blood plasma by radioimmunoassay has been developed. In order to obtain antiserum optically specific to l-pentazocine a hapten-carrier conjugate was prepared from l-pentazocine 2'-carboxymethyl ether by coupling with bovine serum albumin (BSA) using the mixed anhydride method. The antiserum elicited in the rabbit by immunization with this antigen proved to be highly specific to l-pentazocine by cross-reaction studies with the d-form and principal metabolites. The anti-dl-pentazocine antiserum was similarly produced in the rabbit immunized with the dl-pentazocine 2'-caboxymethyl ether-BSA conjugate. The plasma level of d-pentazocine could be estimated indirectly by subtracting the observed value of the l-enantiomer from that of total pentazocine. The plasma concentration of d- and l-pentazocine in man after administration of an officinal dose of the racemate was determined by the established method.