Medications rather than insect bites, pollen or food triggers are a factor in more than one in eight presentations of potentially fatal anaphylaxis, researchers say.
More than 11,500 Australians present to emergency departments after anaphylactic reactions annually, one of the highest documented rates of admission in the developed world.
Case numbers of the severe allergic reaction have increased over 50 per cent since 2017 while almost 20 Australians die each year.
Although most recover, anaphylaxis is always considered a medical emergency and immediately treated with adrenaline.
It most commonly occurs following exposure to substances the patient is allergic to like peanuts or bee stings.
However a team of Victorian researchers have revealed that medications including antimicrobial and anti-inflammatory drugs are implicated in 12 per cent of anaphylactic cases.
Led by Dr George Drewett, an infectious diseases registrar at Austin Health, the study examined more than 4000 episodes of anaphylaxis reported to the Victorian Department of Health over two years.
The work was made possible after authorities listed reactions a notifiable condition, allowing their incidence, cause and characteristics to be analysed for the first time.
Dr Drewett and his team found foods to be the most frequently reported cause, in 2659 or 62 per cent of cases.
Drugs were implicated in 533 cases or 12 per cent and insect venom in 342 or eight per cent. No causes were recorded in 144 or four per cent of cases.
When broken down, it was found antimicrobial drugs were implicated in 258 of the 533 of the drug-related cases (48 per cent) and that of these, 143 were related to penicillin-class agents and 80 to cephalosporins.
Additionally, non-steroidal anti-inflammatory drugs were implicated in 85, or slightly more than one in six, of the drug-related episodes.
While none of the episodes were fatal, hospitalisation was required by more than one-third or 1538 patients and of these, 111 or 2.6 per cent overall, were admitted to intensive care.
The median age in cases of food-related anaphylaxis was 17 years, while for drug-related anaphylaxis it was 45.
Dr Drewett says the findings are consistent with previous retrospective research.
“Our study provides a unique analysis of drug- and antimicrobial-related anaphylaxis, for which prospective data are scarce,” he said.
“Understanding the reasons for and the outcomes of drug-related anaphylaxis in Australia could improve decisions about prescribing and treatment.”
To that end, $27 million in last month’s federal budget will provide for a National Allergy Council and register for anaphylaxis.
An Acute Anaphylaxis Clinical Care Standard was also announced in November which will recommend priority areas for clinicians managing treatment.
Dr Drewett’s findings have been published in the Medical Journal of Australia.