Pharmacotherapy relates to the use of drugs in the prevention and treatment of disease. It is the “art and science” of applying drug-related didactic knowledge (pharmacodynamics and pharmacokinetics) and making therapeutic decisions that are the most likely to benefit a specific patient. Therefore, patient-related variables influence the design, implementation, monitoring, evaluating, and adjusting of drug therapy; and the education and motivation of patients to adhere to therapeutic recommendations.

To determine patient-related variables that will impact on the success or failure of drug therapy, clinicians must gather patient-specific information, i.e., obtain complete and accurate medical histories. From this information the clinician must develop a problem list and identify the potential for drug and/or dosage related adverse effects in “at risk” individuals such as the fetus, an infant, a child, a pregnant woman, a frail elderly, or one with liver and kidney disease; and consider factors that may affect adherence.