BACKGROUND: Measures of medication adherence and persistence are important for researchers and policymakers to assess quality of care. Lack of adherence has been associated with adverse outcomes and higher costs of care. Long-acting medication formulations, including injectable forms, have been proposed as interventions to increase adherence and in turn improve health outcomes and costs. Standard measures of adherence/ persistence were developed for orally administered medications. Methods for assessing adherence/persistence of long-acting injectable dose forms are understudied.