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Measurement of Medication Adherence

            Medication adherence is a growing concern for health care professionals today. For this reason, there are various ways to measure medication adherence. This can be done by pharmacists, physicians, or patients themselves.

            Pharmacists can measure medication adherence through many ways. A cheap and easy way to see if a patient is adherent is to look at the refill rates. These medication adherence rates can be calculated by the medication possession ratio (MPR) or proportion of days covered (PDC). MPR, as stated by Dr. Nau, is the days’ supplied over a time interval. The PDC is the number of days covered by prescription fills divided by the number of days between first fill and the end of the measurement time period. Pharmacist can also measure adherence rates through talking to the patient and asking various questions. The Morisky Medication Adherence Scale provides questions to measure medication-taking behavior such as “Do you sometimes forget to take your high blood pressure pills?” or “how many times this past week have you skipped your medication?”

            Physicians can also measure medication adherence. Poulos and her colleagues made a compilation of direct and indirect approaches to measuring medication adherence.  For example, the physician can obtain lab values for plasma drug concentration, use biological markers, or directly observe the therapy to see if there are sign and symptom improvement. These direct methods of measurement would be useful in finding that the medications have been taken, but it’s use is limited because it is hard for patients to come in for appointments in the outpatient setting, and there are kinetic variations for individual patients. Indirect methods of measuring medication adherence include pill counts, or electronic monitors that show how many times a bottle were opened. These methods are easy to use, however, they cannot show if the medication regimen has actually been followed.

            Patients can measure medication adherence themselves. This can be done through self-reports by the patient, which is the easiest way to get feedback on the medication adherence. Also, patients can keep personal diaries or fill out surveys. These methods are easy to use and inexpensive. However, they may have varying accuracy, lost/not recorded data, and bias. Patients may provide information that can lead to misinterpretation, or patients can present data that overestimates the medication adherence.

            Ways of measuring medication adherence rates can vary from healthcare providers to patients. There is no one-way of measuring medication adherence, however; multiple ways could be implemented to help guide health care practitioners to see how beneficial therapy is and make adjustments to medications. When pharmacists cannot implement certain measures, clinical outcomes should be evaluated to see if the medication is making an impact. After talking to the patient, the pharmacist and patient can find ways to improve medication adherence, so they can achieve appropriate clinical outcomes.

Urvi Patel, PharmD ‘16


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