Impact of Fixed-Dose Combination Drugs on Adherence to Prescription Medications

• Published in: Journal of general internal medicine : JGIM 2008-05, Vol.23 (5), p.611-614
• Main Authors: Pan, Feng, Chernew, Michael E., Fendrick, A. Mark
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Aged; Biological and medical sciences; Brief Report; Diabetes Mellitus - drug therapy; Drug Administration Schedule; Drug Combinations; Drug dosages; Drug therapy; Drug Therapy, Combination; Female; Follow-Up Studies; General aspects; Glyburide - administration & dosage; Glyburide - therapeutic use; Health behavior; Humans; Hypoglycemic Agents - administration & dosage; Internal Medicine; Male; Medical sciences; Medicine; Medicine & Public Health; Metformin - administration & dosage; Metformin - therapeutic use; Middle Aged; Miscellaneous; Patient Compliance; Prescription drugs; Public health. Hygiene; Public health. Hygiene-occupational medicine
• ISSN: 0884-8734; 1525-1497
• DOI: 10.1007/s11606-008-0544-x

Background The inverse correlation between the complexity of a drug regimen and medication adherence is well established. Fixed-dose combination (FDC) therapies are hypothesized to enhance compliance by decreasing the number of required pills. Objective The objective of the study is to compare adherence of a FDC [Glucovance ® , a FDC of metformin and glyburide] to a 2-pill regimen. Design Longitudinal data from a large claims database were used to assess adherence from January 1, 2000, to December 31, 2001. Propensity scoring methods were used to mitigate concerns related to non-random assignment of patients to treatments. Subjects The subjects of the study were individuals prescribed metformin or sulfonylurea or both before July 2000, who were prescribed both metformin and sulfonylurea concurrently (either separately or FDC) after August 2000. Measurements Adherence was measured by medication possession ratio; the proportion of days on which a patient had medication available. Results The FDC enhanced adherence rates by approximately 13% when compared to a 2-pill regimen. Conclusions Compared to 2-pill therapy, a FDC resulted in important increases in patient adherence. Economic analyses are warranted to determine whether the clinical benefits attributable to the adherence gains are worth the incremental cost of a FDC.