The radioimmunoassay of tricyclic antidepressants.

An antiserum to nortriptyline has been produced in a sheep against a nortriptyline-bovine serum albumin conjugate. The conjugate was prepared using the reagent N-(4-bromobutyl) phthalimide followed by a carbodiimide reaction to link the hapten to the carrier protein. The antibodies produced were shown to be specific for the tricyclic group of drugs. The sensitivity of the radioimmunoassay developed is currently limited by the lack of a high specific activity label. The possibilities of developing a radioimmunoassay for nortriptyline in plasma are discussed.