Pharmacogenetics is the scientific discipline seeking to improve the response to drug therapies (better clinical efficiency and reduction of side effects) by taking into consideration the genetic characteristics of the patient. Drugs with a narrow therapeutic index constitute a main target of this emerging field. The combination of therapeutic drug monitoring and pharmacogenetics already allows to optimize the use of some drugs among which oral anticoagulants, immunosuppressants, antiepileptics, antidepressors, antibiotics or antivirals….