Medco is a leading pharmacy benefit manager (PBM), with the nation’s largest mail order pharmacy operations. Through advanced pharmacy, Medco improves the health and lowers the total cost of care for clients and their members, helping to ensure that millions of Americans have access to affordable, high-quality prescription healthcare. No two people respond to the same drug in exactly the same way. In a typical population, there can be as much as a 20- to 30-fold variation in responses to a particular drug. Among the key reasons for such a wide variance are the genetic differences between individuals. Tests for these genetic variations offer physicians a set of powerful predictive tools. By helping to anticipate a patient’s response to a medication more precisely, these tests can help physicians provide truly personalized medicine—selecting the right drug and the right dose for the right patient more quickly, safely, and effectively.