Co-administered orally absorbed drugs in the gastrointestinal lumen

Co-administered orally absorbed drugs in the gastrointestinal lumen refers to the physicochemical environment where multiple medications interact within the stomach or intestines prior to systemic absorption (StatPearls, 2023). These interactions are a major component of pharmacokinetic drug-drug interactions and can lead to significantly altered drug bioavailability (Merck Manual, 2023). Common mechanisms include chelation, where polyvalent metal ions (e.g., calcium, iron) bind to drugs like tetracyclines or fluoroquinolones; adsorption, where resins like cholestyramine bind to other medications; and pH-dependent solubility changes caused by antacids or proton pump inhibitors (FDA, 2020). Such interactions often result in reduced therapeutic efficacy or, in some cases, unpredictable toxicity. While not a specific biological receptor or enzyme, this concept is vital for clinical pharmacology to manage dosing schedules and avoid treatment failure (PubMed, 2021).

Other names

Gastrointestinal drug-drug interactionsLuminal drug interactionsPhysicochemical drug interactionsGI absorption interactions

Physicochemical interactions including chelation, adsorption, and pH-mediated changes in solubility that alter drug bioavailability.