Published online 17 March 2008 | Nature | doi:10.1038/news.2008.676
Corrected online: 19 March 2008

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Adverse drug reactions a big killer

Bad reactions to pharmaceuticals account for 3% of deaths in Sweden.

Pill popping can be bad for your health.Alamy

More than 3% of all deaths seem to be caused by adverse reactions to medical drugs, according to new research.

If substantiated by further work, this would make 'fatal adverse drug reactions' (FADRs) the seventh most common cause of death in Sweden, where the research was done (see 'Top killers'). Unsurprisingly, the team behind the study says that preventative measures should be taken to reduce this figure.

James Ritter, the editor in chief of the British Journal of Clinical Pharmacology — the journal that published the research1 — calls the finding “striking”2. “It is a surprisingly high figure,” agrees Donald Singer, a pharmacology expert at the University of Warwick.

Adverse drug reactions are known to be responsible for between 3% and 12% of admissions to hospitals, and FADRs account for about 5% of deaths of those patients in US hospitals.

One might expect that fewer people in the general population would die because of adverse reactions compared with patients in hospital. But evidence for this trend is hard to come by, says Anna Jönsson, lead author of the new research and a pharmacologist at Linköping University. Previous population-based studies "have been based on death certificates alone", she says. But adverse drug reactions are under-reported on death certificates, she explains.

Case studies

To provide more reliable figures, Jönsson and colleagues looked in detail at one seventh of all deaths in three counties of Sweden in 2001, chosen at random. Two pharmacists and one clinical pharmacologist assessed the case records behind these deaths to pick out possible cases of fatal adverse drug reactions; these were then re-evaluated by another clinical pharmacologist and a forensic pathologist. Only when all agreed was a death categorized as an FADR.

“To the best of our knowledge no previous study has determined the proportion of FADRs on the basis of death certificates in combination with case records, autopsy findings and so on,” says Jönsson.

Of 1,574 deaths, 3% were probably caused by an adverse drug reaction, the authors conclude1. The highest proportion of deaths was from haemorrhage, which are associated with drugs such as aspirin or warfarin, which thin the blood.

Help or hindrance

The study does not necessarily mean that these patients would still be alive had they not received the drugs that apparently killed them.

“This is only looking at one side of the coin,” says Simon Thomas, a therapeutics expert at Newcastle University, UK. “The kind of drugs that cause haemorrhage actually have large benefits. What the figures don’t pick out is the number of patients with cardiovascular risks who don’t have myocardial infarction or stroke because they are taking aspirin.” Thomas adds he wasn't too surprised by the results.

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The researchers are now combing through the case records again to see if they can distinguish whether any of the deaths could have been avoided. Existing literature indicates that between 18% and 70% of all adverse drug reactions are avoidable, says Jönsson.

Better education of patients and doctors could help to reduce the scale of the problem, Jönsson says.

However Singer notes that the study is from a localized part of Sweden and the data are several years old. It is unclear how generalizable the results may be to other areas, he says. 

Corrected:

This article originally stated that the percentage of avoidable FADRs is between 18% and 70%; this statistic is actually for all adverse drug reactions, not just fatal ones.
  • References

    1. Wester, K., Jönsson, A. K., Spigset, O., Druid, H. & Hägg, S. Br. J. Clin. Pharmacol. 65, 573-579 (2008). | Article | PubMed |
    2. Ritter, J. Br. J. Clin. Pharmacol. 65, 451-452 (2008). | Article | PubMed | ChemPort |
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