Inconsistencies of absolute drug-drug-contraindication reports: analysis of Summaries of Product Characteristics of commonly prescribed drugs.

Of 693 analyzed SmPCs, 138 (19.9%) contained ≥1 absolute DDCI. Of 178 SmPCs that referred to sections on "warnings" or "interactions", 131 (73.6%) did not contain further information on absolute DDCI, whereas 47 (26.4%) did. Such additional information was found in sections on "interactions" and "warnings" in 41 (87.2%) and 9 (19.1%) SmPCs, respectively CONCLUSIONS: Information regarding absolute DDCI was found not only in sections on "contraindications" but also in sections on "warnings" and "interactions". Information was not given with consistently straightforward phrasing and structure and so can leave uncertainty for prescribers. To improve drug safety, clear definitions and wording for absolute and relative contraindications should be provided, ideally in tables.