Determination of tricyclic antidepressant, clomipramine (Anafranil), in plasma by a specific radioimmunoassay procedure.

A radioimmunoassay is reported for the tricyclic antidepressant drug, clomipramine (Anafranil, Geigy). Antisera generated in rabbits to clomipramine conjugated to bovine serum albumin at positions 10 and 11 were specific, cross reacting less than 5% with the pharmacologically active metabolite, desmethylclomipramine. Specificity was confirmed by the good agreement in titres observed when the samples were assayed with and without a pre-assay thin-layer chromatographic purification. Intra- and inter-assay variations were less than 8 and 13%, respectively, with a sensitivity of 175 ng/liter. Results obtained agreed well with those reported by other groups using double radioisotope derivative assays. The method has a high throughput rate, one technician can assay 200 samples in duplicate in a working week; and it is sufficiently precise, sensitive, and specific for use in routine minitoring of the drug in plasma and for checking patient compliance with dosage regimen.