A specific method for assay of drug levels in serum of patients treated with clopenthixol decanoate injections.

A fluorimetric method is presented for the simultaneous and specific assay in serum of clopenthixol decanoate, clopenthixol and a clopenthixol metabolite, deprived of the ethanol group in the side chain. The separation is achieved by extractions and thin layer chromatography and fluorescence brought about by treatment with sulphuric acid. The limit of detection in 3 ml serum samples is about 2 ng/ml for clopenthixol and mtabolite, and somewhat higher for the ester. In addition serum data are presented for patients treated with intramuscular injections of 100-600 mg clopenthixol decanoate in Viscoleo every second week. Relatively stable (mean max./min. ratio about 2; maximum after 3-7 days) clopenthixol levels were recorded through-out the dosage interval. Somewhat lower metabolite levels were found. There was no evidence for the presence of clopenthixol decanoate.