Although hypoglycaemia is a known adverse effect of sulfonylureas, limited data exist on the magnitude of this risk among older adults, especially when they are used in combination with other commonly prescribed drugs. Previous research has documented increased hospitalisations for hypoglycaemia with glipizide or glibenclamide following co-administration of several antimicrobial agents; this study sought to investigate this further.
The study used data from Medicare claims in the US (Texas); rates of hospital or emergency department admission for hypoglycaemia within 14 days of a prescription being filled for an antibiotic were calculated. A total of 16 antibiotics were considered – 7 of these were previously implicated in causing hypoglycaemia, whereas 9 had no clear mechanism or evidence linking them to this ADR (and these were used as controls). Five antibiotics were associated with an increased risk of hospitalisations; concomitant use of these antibiotics with sulfonylureas was found to be very common.
The study has a number of limitations due to its design, mainly due to potential confounders of the observed association. For example acute infection could have been responsible for the hypoglycaemia as well as the antibiotic prescription. Although the use of antibiotics thought not to interact as controls mitigates this to some extent, further data in this area are needed to confirm these findings. Another limitation is that hospitalisation and emergency department visits represent only a minority of hypoglycaemic events (the estimated numbers needed to harm may therefore be conservative).
Overall, this research highlights the fact that the risk of hypoglycaemia associated with glucose-lowering medications may be modified by ongoing chronic and short-term therapies, which may potentially interact with them. The prescription of interacting antibiotics to patients receiving sulfonylureas appears to be very common, and is associated with morbidity and thus increased costs.