Spatiotemporal Characterization of Sulfasalazine and 5‐ <scp>ASA</scp> Pharmacokinetics Using a Noninvasive Intestinal Sampling Device

Sulfasalazine, a cornerstone therapy for inflammatory bowel disease, relies on bacterial azo-reduction to release its active component, 5-aminosalicylic acid (5-ASA), which is further metabolized into inactive N-acetyl-5-aminosalicylic acid (N-acetyl-5-ASA) by bacterial N-acetyltransferase. Due to complex pharmacokinetics, patient-specific microbial metabolism, and the lack of accurate, convenient direct sampling method for gastrointestinal drug concentrations, sulfasalazine clinical efficacy remains variable. The CapScan® luminal sampling device enables region-specific, minimally invasive collection of intestinal contents. To better understand sulfasalazine pharmacokinetics in relation to intestinal and systemic drug concentrations and bacterial metabolic capacity, 10 healthy volunteers ingested CapScan devices following sulfasalazine administration. Upon retrieval from the stool, CapScan samples were assigned intestinal locations based on metabolomic and metagenomic profiling. Systemic sulfasalazine peaked at 4 hours post-ingestion, while 5-ASA and N-acetyl-5-ASA peaked at 8 hours. In the gastrointestinal tract, maximal sulfasalazine concentration was observed in the proximal small intestine (SI), decreasing distally as 5-ASA and N-acetyl-5-ASA concentrations increased, peaking in the stool. 5-ASA plasma concentrations positively correlated with distal SI concentrations 4 hours after sulfasalazine ingestion. Putative bacterial azoreductase genes were detected in all gastrointestinal regions, while putative bacterial acetyltransferase genes were detected in all regions except the proximal SI. This study revealed spatially distinct luminal concentrations of sulfasalazine and its metabolites, with a strong correlation between distal SI 5-ASA levels and early plasma exposure, highlighting GI region-specific absorption and microbial metabolism. These findings support the potential utility of luminal sampling to enhance understanding of drug pharmacokinetics and inform future strategies for optimizing oral drug delivery.