Healthy Skepticism Library item: 13483

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Publication type: Journal Article

Aronson JK.
Too high a pedestal
BMJ 2008 Apr 5; 336:(7647):735
http://www.bmj.com/cgi/content/extract/336/7647/735

Abstract:

Observational evidence for determining drug safety

Freemantle and Irs are wrong to say that only properly randomised trials can provide truly reliable evidence on adverse events, just as these are the only source of convincing data on drug efficacy.1 Harms due to drugs differ from benefits in several ways: they are multifarious and affect fewer individuals, some of whom may have particular susceptibilities. Harms often cannot be identified in advance. In some cases these features militate against the practicable use of randomised trials.

If observational studies show no evidence of harms, randomised trials are certainly necessary. They are always desirable, and some adverse effects can be elicited reliably only in this way. However, there are examples of anecdotal reports that provide definitive evidence of both harms and benefits, making randomised trials unnecessary.2 There are also examples of adverse effects that have only emerged from observational studies, having failed to be elicited by randomised studies.3 …

jeffrey.aronson@clinpharm.ox.ac.uk

Notes:

Comment on:
Observational evidence for determining drug safety
Nick Freemantle and Alar Irs
BMJ 2008 336: 627-628.