Some medicines have side-effects (adverse reactions) and may even occasionally cause death. If a genetic variant is found to be associated with an adverse reaction to a certain medicine, doctors could avoid prescribing the medicine to patients with this gene variant.
However, there are other reasons why medicines may be dangerous. These include errors in prescription or administration, patients’ not following instructions accurately, or interactions between medicines or other substances.
Genetic information could be used to adjust the dosage of a medicine, reducing the trial-and-error approach which is often used today to determine the best dose.
Many medicines are not effective for everyone with a particular disease. Some common treatments for diabetes, depression and asthma are only effective in around 60% of patients. Pharmacogenetics could allow doctors to prescribe medicine only for those patients most likely to respond. Alternatively, new medicines could be designed on the basis of genetic information about the cause of disease.