Co-administered orally absorbed drugs in gastrointestinal lumen (None)

Co-administered orally absorbed drugs in the gastrointestinal (GI) lumen refers to the physicochemical environment where multiple medications interact before being absorbed into the systemic circulation (FDA, 2020). This is not a single biological target like a receptor or enzyme, but rather a critical site for pharmacokinetic drug-drug interactions (DDIs) (StatPearls, 2023). Common mechanisms include chelation, where metal ions like calcium or iron bind to drugs such as tetracyclines or fluoroquinolones, forming non-absorbable complexes (Cascorbi, 2012). Additionally, drugs that alter gastric pH, such as proton pump inhibitors, can significantly impact the solubility and subsequent absorption of weakly basic drugs like ketoconazole (Karas, 2017). Adsorption is another key mechanism, where agents like activated charcoal or bile acid sequestrants bind to other drugs in the lumen, preventing their uptake (Journal of Pharmaceutical Sciences, 2015). These interactions are clinically significant because they often lead to reduced bioavailability and therapeutic failure, necessitating careful dosing intervals (NIH, 2021).

Other names

Luminal drug-drug interactionsGastrointestinal pharmacokinetic interactionsPhysicochemical luminal interactionsGI luminal drug interactions

Chelation, adsorption, pH-dependent solubility alteration, and complex formation.