Using pharmacogenomics to personalise drug therapy: which drugs, when and how.

Pharmacogenomic testing provides information on whether a patient possesses gene variants that can influence drug exposure or response. It can be used as part of clinical decision-making to personalise drug therapy. Pharmacogenomic testing can help identify patients at higher risk of serious adverse drug reactions or therapeutic failure, and sometimes it can explain unexpected adverse effects or poor efficacy in patients already on drug therapy. As drug responses are influenced by many factors, pharmacogenomic test results must always be interpreted in the clinical context of the patient. At the time of writing, tests for thiopurine methyltransferase (TPMT) (azathioprine, mercaptopurine, thioguanine) and human leucocyte antigen B*57:01 (abacavir) are Medicare-rebated. Pharmacogenomic testing is also recommended for several other drugs, such as allopurinol and clopidogrel, but these do not currently attract a Medicare rebate.