Medication persistence

Medication persistence may be defined as “the duration of time from initiation to discontinuation of therapy”. Continuing to take any amount of the medication is consistent with the definition of persistence.
This definition can be operationalised in both prospective and retrospective assessments by determining the initiation of treatment, or a point in time during chronic treatment, to a point in time defined as the end of the observation period.
By definition, persistence is reported as a continuous variable in terms of number of days for which therapy was available. Persistence may also be reported as a dichotomous variable measured at the end of a predefined time period (e.g. 12 months), considering patients as being “persistent” or “non persistent.”