[Pharmacogenetics, a valuable aid to therapeutic monitoring of immunosuppressives and antiretrovirals].

Although very effective, some drugs have considerable side effects and are characterized by a relatively narrow therapeutic index. It is therefore sometimes required to regularly check their blood concentration in order to find the best compromise between optimal therapeutic efficacy and reduced toxicity. A therapeutic drug monitoring (TDM) is applied for immunosuppressants used in solid organ transplantation and for antiretrovirals used in the treatment of HIV infections. A first improvement of conventional TDM consists in trying to understand the origin of the inter-individual variability at the pharmacokinetic level in order to anticipate it and to propose individualized dose adjustment according to each patient's genetic characteristics. A complementary improvement consists in measuring the active biological dose of the drug directly in target tissues (lymphocytes for both pharmacological classes considered) and in studying genetic and other factors, influencing this parameter. In complement to conventional TDM, pharmacogenetics therefore allows a better individualization of drug therapy.