[Evaluation of primary adherence to medications in patients with chronic conditions: A retrospective cohort study]

To assess the proportion of members of a private health insurance at the Hospital Italiano de Buenos Aires with primary adherence to, 1) bisphosphonates for secondary prevention of osteoporotic fractures, 2) insulin and metformin in type 2 diabetes, and 3) tamoxifen in the context of treatment of breast cancer.

Retrospective cohort study to determine the proportion of primary treatment adherence during 2012 and 2013. SITE: Hospital Italiano de Buenos Aires, Argentina.

Members of the Hospital Italiano de Buenos Aires private health insurance, who had received a new electronic prescription (alendronate or ibandronate for secondary prevention of fractures following an osteoporotic fracture; insulin and/or metformin for type 2 diabetes; or tamoxifen as a treatment for breast cancer) during the years 2012 and 2013. An analysis was performed on 1,403 new electronic prescriptions, of which 673 were excluded for not meeting the inclusion criteria.

Primary adherence has been defined as the execution of a first-time treatment after it was agreed with the health care provider. The primary analysis assessed the proportion of primary adherence for the three medications. A bivariate analysis was performed to compare the characteristics and potential predictors of primary adherence.

Primary adherence for each drug group was, 93% Bisphosphonates, 88% Metformin, 96% Insulin, and 92% Tamoxifen.

To the best of our knowledge, this is the first study that has evaluated primary adherence in Argentina, and the first for Tamoxifen world wide. The primary adherence documented in our study was somewhat higher than that reported in the literature.