Frequently prescribed oral antibiotics can increase the risk of serious cutaneous adverse reactions in older adults almost threefold, a Canadian study suggests.

While antibiotics were a recognised cause of cutaneous adverse drug reactions (cADRs), University of Toronto researchers said previous studies had not compared the relative risks between antibiotic classes.

Their study found that sulfonamide or cephalosporin use in the past 60 days was associated with a 190% and 160% higher risk of an ED presentation or hospital admission for cADR, respectively, compared with macrolides.

Nitrofurantoin, penicillins and fluoroquinolones were also linked to a higher risk of serious cADRs, while macrolides were used as the comparator because they rarely caused serious cADRs, the researchers wrote in JAMA.