High rates of interpatient variability in drug metabolism and drug response for nearly all medications lead to the hypothesis that assessment of an individual patient's genotype with respect to their ability metabolize certain drugs can be a useful tool in predicting a patient's responsiveness to certain medications. Evaluating patients using pharmacogenomics as a basis for assessment could allow pharmacists to decide which treatment options would be most efficacious in a given patient and, thereby, have significant impact in the clinical setting. This holds true especially in the case of prodrugs, which require in vivo activation to an active or more active form. Codeine is a prodrug whose clinical efficacy depends greatly on its metabolism to more active forms by both cytochrome P450 enzymes and uridine diphosphate glucuronyltransferase enzymes and is affected by the activity of transporters and the structure of its target receptor. Evaluation of a patient's metabolic capacity concerning these enzymes, as well as any "abnormalities" in transporter activity or receptor structure, could indicate if the patient will receive adequate pain relief from a given dose of codeine.