Nonsteroidal anti-inflammatory drugs (NSAIDs) are a therapeutic class suspected to be used by ultratrail runners. The use of NSAIDs during ultratrails is known to be associated with various adverse effects. To study the prevalence of NSAIDs intake in ultratrail runners, oral fluid (OF) is a relevant matrix as it is noninvasive and easy to collect. The aim of our work was to develop and validate a liquid-liquid extraction followed by a liquid chromatography (LC)-mass spectrometry (MS)/high resolution mass spectrometry (HRMS) method for the simultaneous quantification of 19 NSAIDs in OF. After a comparison of different liquid-liquid extraction methods, a double step liquid-liquid extraction with chloroform was performed on OF collected with Quantisal ® , with extraction recoveries higher than 90%. An Accucore AQ column

Ultratrail running is a sport with growing number of adherents. To complete ultratrail despite physical issues such as joint and muscle pain, many runners use nonsteroidal anti‐inflammatory drugs (NSAIDs) and acetaminophen. Studies asking participants about their consumption of drugs during ultratrail revealed a prevalence of NSAIDs and acetaminophen up to 70% and 25%, respectively. The aims of the present study were to determine the prevalence of NSAIDs and acetaminophen for 81 runners during the 2021 Ultratrail du Mont Blanc® (UTMB®) using direct analysis of dried blood spots (DBS) and oral fluid (OF) and to compare results with the declaration of consumption by runners; this is to identify the most relevant method to study the prevalence of drugs. Our results show a prevalence of NSAIDs of 46.6% using DBS, 18.5% using OF, and 13.8% based on a questionnaire. Prevalence of acetaminophen were 30.1%, 30.9%, and 22.5% using DBS, OF, and questionnaire, respectively. From this study, we conclude that the analysis of drugs directly in DBS is the most relevant tool to determine the prevalence in ultratrail events.