Adverse Reactions to Drugs

Abstract

Adverse reactions to drugs can be divided into intolerance, allergy, and idiosyncrasy. With modern methods of testing before marketing, severe and unexpected adverse reactions to new drugs should be uncommon and deaths from intolerance or anaphylaxis should be avoidable by ordinary therapeutic caution. Idiosyncratic reactions may not be discovered till a drug is marketed on a large scale. For this reason a period of surveillance is necessary, during which new drugs are kept under special scrutiny and adverse reactions are promptly reported. Non-fatal or mild reactions to drugs are relatively frequent. It is important that they should be reported so that the relative frequency of their occurrence with different drugs of similar action can be revealed and the more toxic ones can be discarded. The methods at present being used by the Committee on Safety of Drugs are described. The determination of the ratio between the frequency of reactions (the numerator) and the number of patients treated with a drug (the denominator) is at present difficult, but with the steady improvement in the recording and processing of data in the National Health Service it should become progressively easier. © 1965, British Medical Journal Publishing Group. All rights reserved.