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CHAPTER OBJECTIVES

  • Define Medication Therapy Management (MTM) and explain how MTM can improve the success of drug therapy.

  • Explain what “critical-dose drugs” are and name an example.

  • Define therapeutic drug monitoring and explain which drugs should be monitored through a therapeutic drug monitoring service.

  • Calculate a drug dosage regimen in an individual patient for optimal drug therapy for a drug that has complete pharmacokinetic information and for a drug that has incomplete pharmacokinetic information.

  • Explain the relationship of changing the dose and/or the dosing interval on the Cmax(ss), Cmin(ss), and Cav(ss).

  • Define drug–drug interactions and the mechanisms of drug–drug interactions, and provide examples.

  • Define population pharmacokinetics and explain how population pharmacokinetics enables the estimate of pharmacokinetic parameters from relatively sparse data obtained from study subjects.

The success of drug therapy is highly dependent on the choice of the drug, the drug product, and the design of the dosage regimen. The choice of the drug is generally made by the physician after careful patient diagnosis and physical assessment. The choice of the drug product (eg, immediate release versus modified release) and dosage regimen is based on the patient’s individual characteristics and known pharmacokinetics of the drug, as discussed in earlier chapters. Ideally, the dosage regimen is designed to achieve a desired drug concentration at a receptor site to produce an optimal therapeutic response with minimum adverse effects. Individual variations in pharmacokinetics and pharmacodynamics make the design of dosage regimens difficult. Therefore, the application of pharmacokinetics to dosage regimen design must be coordinated with proper clinical evaluation of the patient. For certain critical-dose drugs, monitoring both the patient and drug regimen is even more important for proper efficacy.

MEDICATION THERAPY MANAGEMENT

Medication Therapy Management (MTM) was officially recognized by the United States Congress in the Medicare Prescription Drug, Improvement, and Modernization Act of 2003.1 The objective of this act is to improve the quality, effectiveness, and efficiency of healthcare delivery, including prescription drugs. An MTM program is developed in cooperation with pharmacists and physicians to optimize therapeutic outcomes through improved medication use. MTM provides consultative, educational, and monitoring services to patients to obtain better therapeutic outcomes from medications by the enhanced understanding of medication therapy, improved compliance, control of costs, and prevention of adverse events and drug interactions. MTM programs have been developed for specific practice areas such as elderly care, diabetes, and asthma (Barnett et al, 2009).

INDIVIDUALIZATION OF DRUG DOSAGE REGIMENS

Not all drugs require rigid individualization of the dosage regimen. Many drugs have a large margin of safety (ie, exhibit a wide therapeutic window), and strict individualization of the dose is unnecessary. For a number of drugs generally recognized as safe (GRAS) and effective, the US Food and Drug Administration (FDA) has approved an over-the-counter (OTC) classification ...

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