Does a pharmacist-led medication use review improve medication adherence in polymedicated aged patients? Methodological choices matter!

Rationale, aims and objectives: The rise in chronic diseases urges for an identification of interventions that improve adherence. However, no golden standard exists for evaluating adherence in polymedicated patients. The objectives were to investigate the impact of a pharmacist-led medication use review (MUR) service on adherence implementation rates for chronic medication, and to evaluate the appropriateness of two adherence calculation approaches in this regard. Method: Before-after study (SIMENON study) including ambulatory, aged, polymedicated patients. Refill data were used to calculate the proportion of days covered (PDC) per medication before and after the MUR. Adherence was assessed for chronic, solid, oral medication using a prescription-based and interval-based approach, and the performance of both approaches was compared. Results: Adherence was evaluated for 1483 medications from 316 patients. The median baseline PDC per medication was 0.95 (prescription-based method) and 0.91 (interval-based approach). Pearson correlation between both approaches was 0.616 (P <.0001). The prescription-based approach found less medication below the adherence threshold of 0.80 (319 medications; 21.5% vs 481 medications; 32.4%). Using the prescription-based approach, the proportion of non-adherent patients at baseline was 61.7% (195/316 patients), of which 54.9% (107/195 patients) was only non-adherent for one medication. Median PDC scores increased significantly from 0.95 to 0.99 and 0.91 to 0.99 with the prescription-based and interval-based approach respectively (both P <.0001). Only considering the 319 medications with baseline PDC scores <0.8 using the prescription-based approach, the median PDC scores significantly increased from 0.67 to 0.84 (P <.0001), with a median score improvement of 18.3%. Conclusions: Although baseline adherence was high in this population of polymedicated aged patients, both calculation methods showed the MUR significantly improved adherence. The prescription-based approach was considered the most appropriate method. Based on these findings and literature evidence, it is recommended to implement the MUR service in Belgium and target non-adherent patients for maximal effect.