Information on QT-interval prolongation properties of medicinal products in the european and american drug label

Background: QT-interval prolongation is one of the most common adverse drug reactions leading to regulatory action. Although the occurrence of QT prolongation is generally rare, it can be potentially fatal by causing ventricular arrhythmia. We have noticed that information regarding QT prolonging properties of drugs varies between different sources. Objective: To compare the QT prolonging properties described in the European and American drug label. Methods: The European and American drug labels of products that were centrally approved in Europe between 1.1.2006 and 1.5.2012 were screened. Of those mentioning 'QT', we determined the nature of the message on QT prolongation (no prolongation/unclear drug-QT association/ potentially QT prolongation/QT prolongation). The kappa statistic was calculated to estimate the agreement between the message in the European SPC and the American drug label. Results: Of the 172 selected products approved in Europe, 30 products were not approved by the FDA (44 %). A quarter of the products reported on QT prolongation in both the European and the American drug label (n = 36/142). In one-fifth of the products (n = 28/142), only the American drug label reported on QT prolongation, of which 24 (86 %) contained a negative message (drug does not prolong the QT interval). Two products reported only in the European drug label on QT prolongation (1 %). The agreement on the message about QT prolongation between the European and USA drug label was moderate (kappa 0.42). There was a tendency for the FDA drug label to be more explicit on drug-associated QT prolongation than the European SPC (Unclear message on QT prolongation: FDA 6 %, EMA 12 %). One drug had no QT prolonging properties according to the European label of the EMA, while this drug did prolong the QT interval according to the American label. Conclusion: This study showed that there was moderate concordance between the nature of the QT prolonging effect described in the European and American drug label. The American drug label tended to be more explicit, and more often contained a negative message on QT prolongation than the European drug label.