The Pharmacokinetics Laboratory of the Department of Medical Biology studies the relationships that exist between concentrations of medications and their metabolites (medication transformation products) in plasma and blood cells, and therapeutic response, according to genetic characteristics of individuals or a given population (French Canadians, Amerindians, American Blacks, Asians). These characteristics (or polymorphisms) can translate into a deceleration or an acceleration in the enzymatic transformation of medication and/or an amplification or reduction in medicated response on specific tissue sites. By determining these various variables, it is possible to individualize and optimize therapeutic treatment while minimizing toxic effects.

Our studies with thiopurines (6-mercaptopuirine or Purinethol; azathioprine or Imuran) administered to children have made it possible to validate this axiom. Thus, patients with an activity deficiency of a particular transferase enzyme (thiopurine methyltransferase) have higher concentrations of active metabolites (nucleotides of 6-thioguanine) and a higher percentage of therapeutic response than patients who do not have reduced enzymatic activity. The sex and age of the patient are also determining factors when it comes to the pharmacokinetics of the medication and therapeutic response. Facing the obvious impracticality of performing pharmacokinetics (measuring the concentration of the medication and its metabolites per unit of time) on all drugs administered to children with various ailments, we also studies the possible relationships between the intensity of the drug dose (quantity administered per unit of time) and the therapeutic response as evaluated by various parameters (white blood cell count, gastric acidity, hepatic enzymes). Specialized software makes it possible to determine these relationships.