The research performed was based upon our demonstration that barbiturate-specific antibodies alter pharmacologic response to and disposition of barbiturates. The studies were initially in mice but have now been extended to rabbits which have 100,000-250,000 times higher antibody binding capacities than our mouse colonies and a wider range of antibody binging capacities. The deposition of 3H-phenobarbital was investigated in actively immunized rabbits by assaying serum levels of 3H-phenobarbital at various times prior to and following immunizaton, so individual rabbits served as their own control. A colony of rabbits was immunized and demonstrated to have a high binding ability for barbiturates (ABC50 ranged from 860 to 1462 pmoles/ml undiluted serum). Disposition experiments were done at both low doses of phenobarbital and high (pharmacologic) doses of phenobarbital. It was found that there was an altered disposition of 3H-phenobarbital in immunized rabbits. Antiserum from these rabbits was purified using DEAE cellulose. This procedure resulted in 50-75 fold increase in the specific binding activity per mg of protein in the pooled antiserum. The purified antibody is to be administered to mice for passive immunization and determination of its ability to retain barbiturate binding capability prior to studies on barbiturate disposition in these animals. Further purification was attempted by an affinity chromatography approach. The ligand, 5-allyl-5-(2-carboxyl-alpha methylethyl) barbituric acid, was covalently linked to AH sepharose 4B using 1-ethyl-3-(3-dimethyl-amino-proplyl) carbodiimide to affect the bond. The ligand coupled antibodies from serum but so for the antibodies have resisted attempts at recovery. An altered disposition and response to barbiturates has been previously demonstrated in mice which have circulating barbiturate antibodies.