Pharmacogenetics is already being used and some new uses are just around the corner.

In a small number of cases, doctors are already able to use pharmacogenetic tests in their treatment of patients. For example:

  1. People with HIV are given a test to detect sensitivity to the antiretroviral drug abacavir.
  2. Before patients are given the drug azathioprine, used to treat a variety of conditions, including rheumatoid arthritis, they are tested to find out which genetic variant(s) of TPMT (thiopurine S-methyltransferase) they have. TPMT converts azathioprine into its active form, but some people are unable to do this conversion well because of variation in the TPMT gene. Unconverted azathioprine may build up in the bone marrow and kill developing white blood cells, leaving patients vulnerable to infection.
  3. Trastuzumab (Herceptin) is given to breast cancer patients with mutations in the HER2 gene. The drug was designed specifically to interact with this target molecule.

In addition other uses may soon become common:

  • Tamoxifen, the world's best-selling cancer drug, is metabolised by the cytochrome oxidase enzyme CYP2D6. Patients with some variants of this enzyme will not respond particularly well to it and would be better off with an alternative drug.
  • Warfarin is a drug that is commonly used to thin the blood. It has to be used with care as high doses can lead to dangerous bleeding. It is hoped that pharmacogenetic tests will be able to guide doctors in deciding what dose to give to their patients.

In the longer term, pharmacogenetics is likely to be introduced gradually, as effective example are established. Cancer treatments are likely to be some of the first developed.

The future?

As more and more applications for genetic testing before prescription of drugs emerge, it will become less practical to test individuals each time they are given a drug. A likely scenario is that key genetic information could be determined early in life and stored as part of an electronic medical record. Then, when physicians came to prescribe a medicine, they could refer to patients' genetic records to decide which drugs should be given and which avoided.

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