BMJ  2006;332:488 (25 February), doi:10.1136/bmj.332.7539.488

Letter

Case reports of suspected adverse drug reactions

Case reports were dismissed too quickly

The first 150 words of the full text of this article appear below.

EDITOR—The main difference between the replications by Loke et al of Venning's studies from the 1980s and the original is the evidence that is accepted as further follow-up.¹ Loke et al mention that 56 of 63 case reports on adverse reactions were cited at least once but accept only nine instances as valid follow-up: attempts at proof of mechanisms or controlled studies. However, unexpected adverse effects are by definition due to an unknown mechanism, and many established adverse effects still escape elucidation after years. Moreover, further accumulation of anecdotal reports can be sufficient evidence. A 10 year tally of 22 drugs that were withdrawn from the market showed that 18 were prompted by case reports and only four by a controlled study; for at least 13 the case reports proved sufficient reason for withdrawal.²

A highly unusual event that is repeatedly to an exceedingly high relative risk, a . . . [Full text of this article]

Leiden University Medical Center, 2300 RC Leiden, Netherlands J.P.Vandenbroucke@lumc.nl

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