Antibodies to fentanyl.

Immunization of rabbits with carboxyfentanyl-bovine gamma-globulin conjugate induced antibodies of high titers capable of binding with fentanyl. The antibodies exhibited high average association constants (approximately 1 times 10-7 liter/mol) and were highly specific to fentanyl since no cross-reactivity was observed for a variety of test compounds including other opiates and analgesics. Serological cross-reactivity was observed only for chemicals representing various portions of the fentanyl molecule. These high-affinity, highly selective antibodies have been successfully employed in a radioimmunoassay for fentanyl. Serum concentrations of fentanyl, after administration of 100 and 21 mug/kg/ i.v. in dogs, were determined by this radioimmunoassay. The specificity of these antibodies as compared with the specificity of the pharmacological (opiate) receptor is also discussed.