A new radioimmunoassay for haloperidol: direct measurement of serum and striatal concentrations.

A sensitive and specific radioimmunoassay for haloperidol has been developed. Antibodies were elicited in rabbits immunized with haloperidol hemisuccinate coupled to bovine serum albumin. Optimum sensitivity was obtained with a 1:4000 dilution of the antisera, permitting the detection of as little as 2.6 ng/ml of haloperidol. Major metabolites of haloperidol did not cross-react in the assay. The method does not require an extraction procedure and can be performed using as little as a 5-microliter sample. Haloperidol levels in rat serum and striatum were determined with this method, after the i.v. administration of different dosages of the drug. The distribution and elimination of haloperidol was linear over the dose range to have an elimination half-life of approximately 2.6 hr at all three dosage levels.