Genotype/phenotype comparisons: a probe for the effect of disease progression on drug metabolism.

The effect of disease state on drug metabolism has been investigated using the relationship between genotype and metabolic phenotype. The two polymorphic probes, N-acetyltransferases-2 (NAT2) and cytochrome P450 2C19 (CYP2C19), were respectively used in HIV+/AIDS patients and patients with advanced cancer. The results of the studies suggest that advanced disease produces discordances between genotype and phenotype, indicating a reduction in the metabolic capabilities of these individuals. Thus, polymorphic enzymes such as CYP2C19 and NAT2 can be used to probe changes in drug-metabolizing enzyme capacities. The development of genotype/phenotype discordances should reflect general changes in metabolic capabilities and, thus, alterations in the activities of other important enzymes such as CYP3A. The data also suggest that the genotype/phenotype probes can be used to optimize the clinical treatment of patients with advanced disease states.