Adherence (measured by medication possession ratio [MPR]) was calculated as the proportion of days the patient received the prescribed medication compared to their overall time on therapy (number of days supply, divided by the number of days in the follow-up period [365 days]; days supply beyond the observation window were not included).
The 17-month study measured the medication possession ratio (MPR), proportion of days covered, and refill timing of more than 4,500 patients who received their Diovan in the 30-day color-coded, calendarized reminder package that stated when the prescription should be refilled near the end of the regimen, along with an equal number of patients who didn't get the reminder packaging.
Researchers couldn't measure whether veterans were taking their medications, so they used a common research measure called the medication possession ratio (MPR), which measures how many medication refills the veteran obtained over a year.
To measure adherence status--which was determined by the proportion of days the patient possessed a supply of the medication, or the medication possession ratio (MPR)--a minimum of two claims for the same antidepressant drug was required.
The study found that those patients in commercial drug plans with narrow pharmacy networks had improved medication adherence, as indicated by their medication possession ratio (MPR), which measures patients' available medication on hand over time and is commonly used as an indication of adherence, the authors said.
In addition, enrollees with gaps in their purchases of chronic medication, identified through claims data as < 60 percent adherent over the past 270-day period measure by medication possession ratio (MPR) (Fairman and Motheral 2000) were mailed an educational message that highlighted the importance of medication adherence.