Frequency of adverse drug reactions

Frequency of adverse drug reactions

Whenever possible, an estimate of frequency should be provided, expressed in standard category of frequency. It is always difficult to estimate incidence on the basis of spontaneous reports, owing to the uncertainty inherent in estimating the denominator and degree of under-reporting. However, whenever possible, an estimate of frequency should be provided and in a standard form.
The following standard categories of frequency are recommended:

Very common
> 1/10 (> 10%)
Common (frequent)
> 1/100 and < 1/10 (> 1% and < 10%)
Uncommon (infrequent)
> 1/1,000 and < 1/100 (> 0.1% and < 1 %)
Rare
> 1/10,000 and < 1,000 (> 0.01% and < 0.1%)
Very rare
< 1/10,000 (< 0.01%)