The out-of-focus bias in drug surveillance.

PURPOSE

Existing drug safety systems with phase II and III studies and post-marketing surveillance by principle do not allow for the recognition of an important class of adverse drug reactions (ADRs). ADRs that are resistant to being detected reliably may a) appear as if they are age-related chronic diseases, which also manifest themselves in a high degree without drug treatment, b) arise in "old" drugs, c) arise during long-term application, and d) arise with the administration to frail and aged populations.

CONCLUSIONS

"Silent" and multi-factorial health problems evolving from long-term drug treatment must therefore be addressed with a systematic search strategy, as a third track along with the phase II and III studies and spontaneous reporting systems which still exist.