Pharmacogenetics in the High Street

During development of a new drug molecule, a wealth of information is collected about the new medicine, some of this will end up on the drug label.  It has been estimated that up to 40% of the drug label consists of data of a clinical pharmacology nature; often this may include pharmacogenomic (Pgx) information.  Pgx data may indicate that the drug is metabolised by a cytochromeP450 (CYP450) isoenzyme that is subject to polymorphism.  For example, the isoform CYP450 2D6 (CYP2D6) is subject to polymorphism which is reflected in people having poor or extensive metabolic activity via this route.  Codeine is metabolised to its active form morphine via CYP2D6.  People who are CYP2D6 poor metabolisers have a high probability of an inadequate analgesic response to codeine. 

A recent report in the Clinical Pharmacist stated that in Australia people can walk into their local pharmacy and be tested for a variety of polymorphisms that could affect their response to a particular medication.  Within a week of the test, the patient’s pharmacist and GP receive the result.  This personalised approach to prescribing allows the prescriber to select the therapeutic agent that is most likely to maximise the benefit/adverse event ratio for the patient.  An individual is required to take a Pgx test only once, but the information obtained lasts a lifetime.

In the UK optimised prescribing using Pgx data lags far behind the Australian model.  Pgx information is often available in the drug label, but its use to optimise therapy is rare.  NHS England has launched an initiative aiming to make whole-genome sequencing standard practice by 2020.  Wright & Bhatt suggest that pharmacists, in both primary and secondary care, could be at the forefront of initiating and interpreting Pgx data, thereby playing a pivotal role in the optimisation of a patient’s drug therapy1. To ensure pharmacists can take on this role they suggest that undergraduate courses need to include practical training in Pgx, additionally, training is required for those already in practice.

Such an opportunity serves to broaden the appeal to those community pharmacy, developing innovative clinical services that have a direct impact on their customers, not a slave to the dispensing machinery.

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