Pharmacogenetics: Mismatches between policy and practice

Pharmacogenetics (PGx) and personalised medicine are new disciplines that, gathering the existing knowledge about the genetic and phenotypic factors that underpin drug response, aim to deliver more targeted therapies that avoid the existing problems of adverse drug reactions or lack of drug efficacy. These disciplines imply a shift in the way drugs are prescribed, as they require introducing diagnostic tools and implementing pre-screening mechanisms that assess patients' susceptibility to new or existing drugs. The direct benefit is an improvement in drug safety and/or efficacy. However, neither PGx nor personalised medicines are widely used in clinical practice. They both face a series of gaps in knowledge that hamper their widespread use in clinical practice. This paper illustrates, through the case of TPMT (thiopurine methyltransferase) testing for preventing adverse events caused by the drug azathioprine, how the use of personalised medicine is being shaped by user-producer mechanisms and negotiated between different actors involved in the process of drug development and service delivery. The paper uses concepts of the sociology of science and a qualitative approach to explore the existing mismatches between PGx policy and practice.