The profession pharmacy deals with proper delivery of drug therapy to patients. However, it has long been confined to mere delivery of drugs without including the use, evaluation and monitoring of drug therapy for the patients. The increasing number of adverse drug reactions and drug costs over the years has led the government to focus on the role of pharmacists in effective drug use by the patients. As a result, the US government passed the Medicare Modernization Act of 2003 and Medicare Prescription Medication Benefit (Part D), incorporating medication therapy management (MTM) services.

The act mandates the prescription drug plan sponsors of Medicare Part D and Medicare Advantage Plans implementing drug benefit under Part C to provide medication therapy management in order to ensure proper drug use and minimization of adverse drug reactions. The MTM program aims at those beneficiaries of Medicare who are using multiple drugs for multiple chronic conditions, incurring high drug costs. It means that the service is primarily targeted at beneficiaries eligible for Medicare Part D and incurring annual drug costs beyond the specified level of the Department of Health and Human Services, which was approximately equal to or more than $4,000 for 2006. The MTM service market can also involve nonbeneficiaries of Medicare Part D who are ready to pay their own money to join the program.

The pharmacy profession defined MTM as “a distinct service or group of services that optimize therapeutic outcomes for individual patients that are independent of, but can occur in conjunction with, the provision of a drug product". Also, the Center for Medicare & Medicaid Services defines MTM as a mechanism for ensuring “medications prescribed for targeted beneficiaries are appropriately used, optimizing therapeutic outcomes and reducing the risk of adverse events".

The definition of MTM given by 11 national pharmacy organizations in July 2004 includes the following aspects: Obtaining required assessments of the patient’s health status, establishing a medication treatment plan, selecting, initiating, modifying, or administering medication therapy, evaluation of patient’s response to therapy, following a comprehensive medication review to prevent adverse drug events and other medication-related problems, documenting data and communicating information to patients and primary care providers when required, enhancing patient’s understanding of proper drug use through education and training, providing information and resources to improve patient’s adherence to therapeutic regimens, integrating MTM into the healthcare management services that are offered to the patient
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The above aspects are also considered as the core elements of MTM formulated by the American Pharmacists Association and the National Association of Chain Drug Stores Foundation.

Beneficiaries are mostly patients with multiple chronic diseases, using multiple drugs under Part D and incurring higher annual drug costs than set levels. The main considerations include the existing data on the incidence and prevalence of chronic diseases in the Medicare population, the availability of treatment guidelines and effectiveness evidence of drug therapy in the treatment protocols. The criteria to identify drug use include the use of multiple drugs, combinations of drugs used and nonuse of indicated drugs, among others. The patient’s drug costs are determined by the track record of various healthcare costs that indicate whether or not the costs are beyond the set level. Other patients who visit multiple physicians and/or pharmacists, and/or lack evidence of coordination of care can be considered for MTM service.