Introduction

Paradoxical adverse drug reactions (ADRs) are defined as being opposing reactions to the pharmacological effect of drugs in relation to its pharmacodynamic properties. Their diagnosis is difficult as they are relatively rare with atypical clinical presentation (with the possibility of being confused with drug ineffectiveness or the worsening of the underlying disease). This kind of ADR may be particularly subject to under-notification. The aim of the present study is to describe paradoxical ADRs using the French PharmacoVigilance DataBase (FPVDB).

Method

We analysed all reports recorded in the FPVDB with drugs defined as “suspect” and which included the term “paradoxical reaction” (PR) (according to MedDRA classification) from 01/01/1984 to 12/31/2018. The drugs were classified according to the Chemical Therapeutic Anatomical Classification (ATC).