Medication Adherence Measures: An Overview

Table 1

Equations of medication adherence measures involving secondary database analysis and pill count [15, 19, 27, 28].

Measures	Equation
Medication Possession Ratio (MPR)	Days’ supply obtained/refill interval or fixed interval
Dichotomous variable	N/A; (arbitrary cutoff value)
Continuous, Multiple Interval Measure of Medication Acquisition (CMA)	Cumulative days’ supply obtained over a series of intervals/total days from the beginning to the end of the time period
Continuous, Multiple Interval Measure of Medication Gaps (CMG)	Cumulative days without any medication over a series of intervals/total days from the beginning to the end of the time period
Continuous, Single Interval Measure of Medication Acquisition (CSA)	Days’ supply obtained in each interval/total days in the interval
Continuous, Single Interval Measure of Medication Gaps (CSG)	Number of days without any medication/total days in the interval
Pill count	(Number of dosage units dispensed − number of dosage units remained)/(prescribed number of dosage unit per day × number of days between 2 visits)