Measurement of plasma etoposide by radio-immunoassay. 
A sensitive radioimmunoassay (RIA) for the specific determination of 4'-demethylepipodophyllotoxin-1beta(4,6-O-ethylidene)-alpha-d-glucopyranoside (etoposide) in human plasma is described.  In order to obtain a specific antisera, etoposide-acetonyl-carboxymethoxime-bovine serum albumin (BSA) and etoposide-hemisuccinate-BSA conjugates were synthesized as antigenic hapten carrier proteins.  Antisera raised against both conjugates in rabbits and sheep exhibited high specificity and made it possible to discriminate etoposide from picro-etoposide and picro-hydroxy acid.  Good correlation was found in a comparison of the new RIA method with one method involving high-performance liquid chromatography (r = 0.9792).  The method was applied to the direct analysis of etoposide in plasma obtained from cancer patients.