[What information is given on adverse drug reactions from new drugs?].
BACKGROUND: It is not known to what extent information on previously unknown adverse reactions is communicated to doctors after the approval of a new drug. MATERIAL AND METHODS: We included seven drugs, approved between 1982 and 1995 and the first in their class to be approved in Norway. We recorded the number of adverse reactions listed in the annual editions of the Norwegian physicians' desk reference(Felleskatalogen) from the first edition that included the drug and up until the 2001 edition. RESULTS: Only 51 % of the adverse reactions listed in the 2001 edition were included in the first post-approval edition. On average, 1.6 new adverse reactions were added for each drug every year. By contrast: in a group of 12 drugs approved before 1970, 0.14 new adverse reactions were added for each drug every year between 1989 and 2001. INTERPRETATION: With a new drug it is to be expected that many adverse reactions are not acknowledged as such. Caution is warranted because of the fact that even though it is not listed in the physicians' desk reference, any event appearing in a patient exposed to a new drug may be an adverse reaction.