Changes in pharmacological responses, conditioned by polymorphic enzymatic forms, will produce variant pharmacogenetic phenotypes, related to sub-dose effects or drug toxicity.

Pharmacogenetics is defined, through genome (DNA) analysis and its products (RNA and proteins), as the possible relationship with drug response.

Pharmacogenetics, along with genomics, promises individualized pharmacotherapy, by studying the genotype of each individual, adapting the genome to a safe drug response, reducing the probability of adverse events.

Pharmacogenomics is defined as the variability of drug responses due to inherited characteristics, studying the variabilities in drug responses attributed to hereditary factors in different populations.

Cytochrome P450 enzymes belong to a select family of chromoproteins widely distributed in all living organisms and are involved in the metabolism of a variety of chemically different compounds.