• Measurement of chlorpromazine and metabolite levels in the blood has not yet developed such that it can help the clinician. Apart from their chemistry, the clinical aspects of the experimental design of most studies leave much to be desired, so that it is not possible to draw any overall conclusions about the relationship between chlorpromazine blood levels and clinical outcome from the data currently available.
Measurement of response to a single test dose may prove potentially more fruitful in predicting outcome and in establishing drug and dosage choice for a given patient than simple attempts to correlate sustained dosage levels with clinical response.
For chlorpromazine, indeed for any drug, it would seem wise in the first instance to focus clinically well-designed studies on the parent substance, rather than launching into more costly, but clinically unsophisticated, studies of its metabolites.
May PRA, Van Putten T. Plasma Levels of Chlorpromazine in SchizophreniaA Critical Review of the Literature. Arch Gen Psychiatry. 1978;35(9):1081-1087. doi:10.1001/archpsyc.1978.01770330055004