The variability of a drug's response between patients is an expected feature of most drug treatments, it can lead to therapeutic failures or unwanted adverse drug reactions. This therapeutic phenomenon is increased by pharmacokinetic variability implying that, for the same dose, the effective drug concentration in body fluids is highly variable. In addition to pharmacokinetics, the interindividual pharmacodynamic variability impacts the response of receptors in equal concentration of drug. This work is focused on polymorphism in drug metabolizing enzymes, especially N-acetyltransferase 2 (NAT2).