ABSTRACT
The response to pharmacologic agents varies tremendously by individual. For instance, the plasma level of a given medication can vary more than 1000-fold between two individuals having the same weight when treated with the same drug dosage.1 On average for a given drug, 30 percent of patients show beneficial effects, 30 percent fail to improve, 10 percent only experience side effects, and 30 percent are noncompliant (which may be related to either lack of efficacy or side effects).2 Therefore, as many as 70 percent of all patients are unnecessarily exposed to the potential to develop adverse drug reactions (ADRs).3-5 In 1994, over 2 million ‘serious ADRs’ and over 100 000 fatal ADRs were noted, ranking ADRs between the fourth and the sixth leading cause of death in the USA.6 Overall, the cost of drug-related morbidity and mortality exceeded $177.4 billion in 2000,7 a figure more than double the estimate from 1995.8 As enormous as these figures are, some authorities feel that the burden due to lack of therapeutic response to drug therapy is much greater.9
