Doxycycline (DOX) is a well-characterized antibiotic, and its pharmacokinetic behavior has recently attracted renewed scientific interest. Its absorption occurs mainly in the small intestine, while ions such as Fe3+ and Al3+ readily form complexes, particularly under acidic conditions, thereby reducing the fraction of free drug available for absorption. The present study provides a systematic investigation of how such interactions influence the dissolution and intestinal permeability of DOX. A dynamic in vitro protocol was implemented, incorporating an online transition from gastric to intestinal conditions in combination with Franz diffusion cells. This integrated system enables real-time monitoring of early DOX absorption-related processes, providing a more comprehensive understanding of potential pharmacokinetic interactions during its coadministration with iron or aluminum supplements. To ensure reliable quantification, a rapid, economical, and environmentally compatible HPLC-FLD method was developed and validated, employing a Hypersil Gold C18 column (50 mm × 4.6 mm, 5 μm; Thermo) and a mobile phase consisting of acetonitrile—20 mM NaH2PO4 (pH 2) 15:85 v/v. Overall, a practical and efficient framework was established for investigating factors that influence the bioavailability of doxycycline, supporting the broader evaluation of drug, excipient, and drug supplement interactions.
Kamaris et al. (Fri,) studied this question.
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