Drug interactions related to self-medication: a French pharmacovigilance database study

Self-medication (SM) is a common practice perceived by patients as harmless which can, however, entail health risks. The aim of the study was to identify drug-drug interactions (DDIs) involving SM drugs leading to adverse drug reactions (ADRs) in the National French Pharmacovigilance Database. All ADR reports from 1 January 1985 to 31 July 312018, coded as 'interaction' and 'self-medication', were selected and studied. Patient characteristics, the level and type of interaction, and the therapeutic classes of the drugs were examined. Adverse drug reactions were analysed and classified according to the system organ classes of the Medical Dictionary for Regulatory Activities. One hundred and three reports totalling 158 ADRs (71% severe cases) were included; 153 DDIs (59.5% pharmacodynamic) involving 234 drugs were identified. The latter included 119 SM drugs (51% available on prescription), mainly analgaesics, anti-inflammatory drugs, dietary supplements and antibiotics. Haemostasis disorders and renal failure were the most frequently reported ADRs. The analysis of reference documents raised concerns on the lack of information provided by package leaflets. In conclusion, the present study highlights the risks of medically unapproved re-use of prescription drugs or the consumption of dietary supplements without monitoring possible interactions and ADRs. Patient awareness could be improved by more regular updates of medication package inserts.