Off-label use of prescription medicines seems to increase the risk of adverse drug events, according to new research in JAMA Internal Medicine.

A study enrolled 46,021 patients, who experienced 3,484 adverse events (13.2 per 10,000 person-months). One in eight (11.8 per cent) prescriptions were off-label. Overall, adverse events were 44 per cent commoner with off-label than on-label use (19.7 and 12.5 per 10,000 person-months respectively) after adjusting for various confounders.

“Strong scientific evidence” does not support 81 per cent of off-label use, the authors say. Adverse event risk was 54 per cent higher for unsupported off-label use than for indications with a robust evidence base (21.7 and 13.2 per 10,000 person-months respectively).

The risk of adverse events with off-label use supported by strong scientific evidence was not significantly different from on-label use. The authors call for caution over drugs for “offlabel uses that lack strong scientific evidence”.

^{(doi:10.1001/jamainternmed.2015.6058)}