Introduction

Multiple variables influence the selection and optimization of drug therapy for each individual patient. Pharmacogenomics, the study of the influence of individual genetic variations on drug response in patients, may yield additional information to further enhance safe and effective medication use. Originally the field focused on the effects of specific variants within individual genes on drug response (i.e., pharmaco genetics), however more recent research has focused on the role of multiple variants across the genome (i.e., pharmaco genomics) and their combined potential to modify and alter drug therapy outcomes.

The understanding of pharmacogenomics has increased considerably. Most emerging research has fallen into one of three domains:

• Gene variants that influence the function of drug transporter proteins (how efficiently drugs are delivered to their site(s) of activity)
• Gene variants that cause differences in the function of drug metabolizing enzymes (how quickly or slowly drugs are utilized and broken down in the body)
• Gene variants that alter a drugs' "target" proteins (variations in the genes coding for a target protein may alter the protein's three-dimensional shape, changing the binding affinity for drugs to that protein)

As the biological relevance of specific genetic variants has increased, it is understood that multiple variations across the genome can contribute to significant, yet relatively predictable treatment outcomes. Virtually every therapeutic area involving medication use includes a drug for which documented genetic variability has the potential to affect drug response. Some of this information is included in the FDA-approved package insert prescribing information. For some agents, the suitability of a specific drug or the determination of an appropriate initial dose for an individual patient based on pharmacogenetic information has been incorporated into dosing algorithms and patient care. As such, it is essential that health care professionals can interpret and utilize this information to facilitate safer and more effective use of medications for individual patients.