New drugs: watch out for unexpected adverse effects.

(1) Some serious adverse drug reactions only emerge once a drug has been released on to the market. (2) 10% of the new drugs marketed in the United States over the last 25 years were subsequently withdrawn or were the subject of major warnings about serious or life-threatening side effects. The number of patients affected is unknown. (3) Patients must not be placed at risk because doctors prescribe a new drug when a reliable alternative is available or when the condition treated is mild. (4) Prevention should be based on improved quality of clinical trials and on upgraded procedures for marketing approval. Other measures include encouraging the correct use of recently marketed drugs; closer monitoring of these drugs; better notification of side effects; and improved quality and transparency of pharmacovigilance data.