The Medication Possession Ratio (MPR) is the ratio of a patient's drug supply based on pharmacy records to the amount needed for continuous therapy. This can help identify patients who may be nonadherent to drug therapy.
medication possession ratio =
= (number of days covered by drugs received) / (number of days that need to be covered for continuous drug therapy)
Ratio
Interpretation
< 0.8
poor adherence
0.8 - 1.1
good adherence
> 1.1
excess drug refills
Some causes for poor adherence:
(1) free drug samples
(2) prescription filled at another pharmacy
(3) admitted to the hospital for a prolonged period
Some causes for excess drug refills:
(1) lost medication
(2) change in prescription with excess drug provided
(3) diverting medication (if abuse potential)
Limitations:
• This is a relatively crude screening tool. A person could have filled a prescription and not taken the medication.
• This could be useful for monitoring a patient on a long-term medication at stable dosing.
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