The bone risk in women was previously highlighted in other trials, including a major one that reported late last year. The issue has been overshadowed recently, however, by a critical study published in May, which argued Avandia was linked to increased heart attack risk. That news sent prescriptions for Avandia, Glaxo's second biggest drug, plunging.
Analysts at Morgan Stanley say the latest data was an incremental negative which, coupled with results from past trials, added to the likelihood Avandia's label would be toughened to include stronger warnings about bone safety.
Glaxo, however, cautioned against reading too much into the latest results. "The findings of this study are limited as it involves very low patient numbers and, as a retrospective study, it is not possible to draw meaningful comparisons nor rule out confounding factors, such as age and duration of diabetes," a Glaxo spokesman wrote Reuters.