Compared to other bisphosphonates, alendronate was associated with a higher number of Clostridium difficile infection (CDI) adverse drug reactions, as indicated by the Food and Drug Administration (FDA) Adverse Event Reporting System data (FAERS).

To further assess the previously noted associated between CDI and non-antimicrobial medications, researchers carried out a disproportionality analysis of adverse drug reactions (ADR) using FAERS data.

A total of 4.2 million reports from 1997 to 2014 were analyzed, these included 6,743 CDI reports, comprising 0.16% of all ADR reports. Four major measures of association are used to describe reports: reporting odds ratio (RORs), proportional reporting ratio (PRR), information component (IC) and empirical Bayes geometric mean (EBGM). 

Related Articles

Results showed that alendronate was the only agent that met the signal criteria for all four measures, with 0.44% (103/23,603) reports of CDI. Risendronate had 0.44% (16/3,672) CDI reports and was disproportionately higher by ROR, PRR, and IC but not the EBGM. Ibandronate – with 0.21% (17/7,945) reports – did not meet any of the significant measure criteria.   The signal was shown to be strongest for women and those 40 years of age and older.

The authors state to their knowledge this is the first report to highlight a possible association between alendronate and CDI. A possible underlying reason for the link with CDI, the authors point out, is that alendronate was the first FDA-approved bisphosonate and therefore has by far the largest number of overall reports.

The study of safety signals can be the first step in identifying serious ADRs, as an example, the authors point to the FDA using reports to highlight the unusual drug-ADR relationship with isotretinoin and depression.

However, the findings from this analysis; that of the disproportionately high number of CDI ADR reports with alendronate use, must be interpreted with caution. “Further research using a robust data source is needed to understand this unusual ADR safety signal,” conclude the authors.

For more information visit