Today in medicine, it is common that physicians often use a trial and error strategy until they find the treatment therapy that is most effective for their patient. With personalised medicine, these treatments can be more specifically tailored to an individual and give insight into how their body will respond to the drug and if that drug will work based on their genome. The personal genotype can allow physicians to have more detailed information that will guide them in their decision in treatment prescriptions, which will be more cost-effective and accurate. As quoted from the article "Pharmacogenomics: The Promise of Personalised Medicine", “therapy with the right drug at the right dose in the right patient” is a description of how personalized medicine will affect the future of treatment. For instance, Tamoxifen used to be a drug commonly prescribed to women with ER+ breast cancer, but 65% of women initially taking it developed resistance. After some research by people such as David Flockhart, it was discovered that women with certain mutation in their CYP2D6 gene, a gene that encodes the metabolizing enzyme, were not able to efficiently break down Tamoxifen, making it an ineffective treatment for their cancer. Since then, women are now genotyped for those specific mutations, so that immediately these women can have the most effective treatment therapy.