Adherence and persistence of patients using oral bone sparing drugs in primary care.

Aim. Studies based on pharmacy medication records have shown suboptimal adherence and persistence of osteoporosis treatment with oral bone sparing drugs (OBSD). Little is known about adherence and persistence of OBSD treatment in primary care. We assessed adherence and persistence of OBSD use of patients in general practices and identified associated factors. Methods. Using electronic medical records, adherence and persistence of newly prescribed treatment with OBSD in patients from 16 general practices was retrospectively assessed. The Medication Possession Ratio (MPR) was calculated as a proxy for adherence (MPR > 75%), persistence rates were estimated using survival analysis. Determinants of adherence and persistence using logistic regression and Cox regression analysis were assessed. Results. OBSD treatment was initiated in 957 patients. Seventy-five percent and 45% of the patients persisted OBSD treatment for one and five years, respectively. Being adherent in the first year decreased the risk of long-term non-persistence [hazard ratio (HR) 0.41; 95% confidence interval (CI) 0.3-0.57; P < 0.001]. Patients receiving the majority of their prescriptions by a specialist tended to be more non-persistent (HR 1.37; 96%; CI 0.96-1.94; P = 0.08). Adherence was 62.5% in the first year and 60.8% in the overall treatment period. Non-adherence was associated with the specialist being the main prescriber [odds ratio (OR) 3.76; 95% CI 2.43-5.82; P < 0.001] and younger age (< 65 years, OR 1.44; 95% CI 1.01-2.08; P = 0.04). Conclusion. Older age of the patients and the GP prescribing the majority of medication were associated with better adherence and persistence. Good adherence in the first prescription year was associated with better persistence.