The changing patterns of dispensing branded and generic drugs for the treatment of gastroesophageal reflux disease between 2006 and 2011 in Japan: a retrospective cohort study

BACKGROUND Despite rising healthcare costs, generic drugs are less frequently dispensed in Japan compared with other developed countries. This study aimed to describe changes in dispensing of branded and generic drugs and to explore possible factors that promote the use of generic drugs. METHODS We conducted a retrospective cohort study using a Japanese medical and pharmacy claims database. All proton pump inhibitors (PPIs) and histamine H2-receptor antagonists (H2RAs) with indications for gastroesophageal reflux disease (GERD) described on Japanese labels were included. Patterns of dispensing branded and generic drugs for the treatment of GERD between 2006 and 2011 were analyzed. Multivariate logistic regression was applied to investigate factors associated with receiving generic drugs. RESULTS The study cohort included 14,590 patients (male: 50.2%, mean age: 43.1 years). Branded drugs for GERD were still frequently dispensed despite an increase in the share of generic drugs. Only 4.3% of patients who initially received branded drugs switched to generic drugs. The percentage of patients who received only generic drugs increased over time (6.5% to 22.1%). The frequency of generic drug dispensing was the highest in the setting where both prescription and dispensing were implemented in clinics (43.3%), while the lowest in the setting where both prescription and dispensing were implemented in hospitals (11.5%). Factors associated with receiving generic drugs included year of dispensing (adjusted OR 2.22, 95% CI 1.94 to 2.55 for 2009-11 v 2006-8), prescription and dispensing setting (OR 1.81, 95% CI 1.44 to 2.26 for prescription in hospitals and dispensing in community pharmacies; OR 2.21, 95% CI 1.80 to 2.72 for prescription in clinics and dispensing in community pharmacies; and OR 4.55, 95% CI 3.68 to 5.62 for prescription and dispensing in clinics v prescription and dispensing in hospitals) and H2RAs (OR 1.64, 95% CI 1.49 to 1.81 compared to PPIs). CONCLUSIONS The share of generic drugs for the treatment of GERD increased over time although branded drugs for GERD were still dispensed frequently. The use of generic drugs for GERD was influenced not only by government policies but also by changes in treatment approach and the setting of prescription and dispensing.