Medication compliance and persistence: terminology and definitions.

Objective: The aim of the study is to provide guidance regarding the meaning and use of the terms "compliance" and "persistence" as they relate to the study of medication use.

Methods: A literature review and debate on appropriate terminology and definitions were carried out.

Results: Medication compliance and medication persistence are two different constructs. Medication compliance (synonym: adherence) refers to the degree or extent of conformity to the recommendations about day-to-day treatment by the provider with respect to the timing, dosage, and frequency. It may be defined as "the extent to which a patient acts in accordance with the prescribed interval, and dose of a dosing regimen." Medication persistence refers to the act of continuing the treatment for the prescribed duration. It may be defined as "the duration of time from initiation to discontinuation of therapy." No overarching term combines these two distinct constructs.

Conclusions: Providing specific definitions for compliance and persistence is important for sound quantitative expressions of patients' drug dosing histories and their explanatory power for clinical and economic events. Adoption of these definitions by health outcomes researchers will provide a consistent framework and lexicon for research.