Clinical pharmacology. Adverse reactions to drugs.

Adverse drug reactions (defined as unintended effects of substances used in the prevention, diagnosis, or treatment of disease) are common. They are responsible for 3-5% of hospital admissions, occur in 10-20% of hospital inpatients, and have recently been reported in 40% of patients receiving drugs in general practice.' Thompson and 12 have suggested that adverse reactions and interactions can usually be logically and clinically divided (see table 1) into those that form part of a drug's normal pharmacological actions (type A: augmented), and those that represent a novel response (type B: bizarre).