Brand versus generic alendronate: gastrointestinal effects measured by resource utilization.

BACKGROUND

Adverse reactions related to the upper gastrointestinal tract (UGIT) that are associated with generic alendronate formulations may differ from those associated with the brand drug.

OBJECTIVE

To test the hypothesis that adverse UGIT effects of alendronate formulations may differ between generic and brand products.

METHODS

We conducted a database health resource utilization analysis of UGIT outcomes in patients who started treatment with generic or brand alendronate formulations during 2001-2005. We included 6962 patients who were treated continuously for 3 months with 1 of 4 alendronate formulations: brand 10 mg/day (Merck, Sharpe & Dohme, n = 1418), generic A 10 mg/day (Teva, Israel, n = 650), generic B 10 mg/day (Unipharm, Israel, n = 628), and brand 70 mg/wk (n = 4266). In these patients, who had neither filled a prescription for alendronate nor had any gastrointestinal problems in the year preceding the study, we compared incidence rates of new use of gastric medications (H2-blockers, proton-pump inhibitors, or antacids), gastroenterology visits, endoscopies, and hospital admissions.

RESULTS

Incident rate ratios (IRR) for treatment discontinuation were higher with both daily generic products (IRR 1.3; 95% CI 1.04 to 1.63). Adherence (medication possession ratio [MPR] >80%) was better with brand 10 mg/day (IRR 1.19; 95% CI 1.11 to 1.27). All comparisons were adjusted for use of concurrent corticosteroids, nonsteroidal antiinflammatory drugs, and potassium supplements. Hospitalization rates (2.7-3.2%) were similar in all groups. New use of gastric medications (3.4-4.9%) was lower with brand 10 mg/day (IRR 0.71; 95% CI 0.53 to 0.95). Rates of UGIT endoscopy (n = 49) in patients receiving 10 mg were 0.6% (brand), 1.1% (generic A), and 1.6% (generic B), with generic B higher (IRR 2.88; 95% CI 1.14 to 7.29) in the entire cohort, but not among new users (n = 273) of gastric drugs (IRR 2.46; 95% CI 0.55 to 11.05). Endoscopic findings were normal in 22 patients, hiatal hernia with no mucosal lesion was present in 10 patients, and there was mild-to-moderate esophagitis or gastritis in 17 patients; there were no significant differences among the formulations.

CONCLUSIONS

We found insufficient evidence to indicate major differences in UGIT adverse effects related to use of daily generic, as compared with brand, alendronates.