Therapeutic ineffectiveness is a frequent drug-related problem that can occ
ur in a variety of different situations and be caused by different mechanis
ms. Examples are inappropriate use, interactions or metabolic abnormalities
. Observations in patients of unexpected ineffectiveness can provide import
ant information with regard to such situations. Therefore, ineffectiveness
- especially when unexpected or unexplained - is a potentially important re
portable event in pharmacovigilance. The terms regarding ineffectiveness in
the WHO Adverse Reaction Terminology (WHOART) have been recently revised i
n order to enable optimal coding of such case reports.