Development of a Dual-Trigger pH- and Microbiota-Responsive Budesonide Tablet for Regioselective Colonic Delivery: In Vitro, Pharmacokinetic and Pharmacodynamic Evaluation

Abstract

Site-specific oral therapy of inflammatory bowel disease is limited
by physiological variability in gastrointestinal pH, transit and luminal
conditions. Budesonide is a potent locally acting glucocorticosteroid whose
extensive first-pass metabolism makes it particularly suitable for regional
gastrointestinal delivery. Current extended-release budesonide is clinically used
at 9 mg once daily for induction of remission in mild-to-moderate ulcerative
colitis, supporting the therapeutic relevance of formulation-controlled colonic
delivery. [1]
Objective: To develop and comprehensively evaluate a Quality-by-Designoptimized,
pH- and microbiota-responsive budesonide tablet for preferential
colonic delivery.
Methods: A 9-mg budesonide core was surrounded by a compression coat
comprising pectin, guar gum and hydroxypropyl methylcellulose (HPMC) and
subsequently coated with a pH-responsive methacrylate polymer. A three-factor
Box–Behnken design evaluated the effects of pectin/guar-gum composition,
HPMC amount and enteric-coating weight gain. Critical responses were drug
release at 2, 5 and 8 h and T10. The optimized formulation underwent
physicochemical characterization, sequential gastrointestinal dissolution,
microbial/enzyme-triggered release, ex vivo tissue-retention assessment,
gastrointestinal localization, pharmacokinetic and tissue-distribution studies,
experimental-colitis pharmacodynamics, systemic safety assessment and
stability testing.
Results: The illustrative optimized composition contained budesonide 9 mg,
pectin 86 mg, guar gum 64 mg and HPMC 52 mg with 8.4% enteric-coating
weight gain. Drug release was 1.67 ± 0.16% at 2 h, 7.12 ± 0.22% at 5 h and
84.42 ± 0.41% at 8 h†. The optimized system demonstrated delayed systemic
exposure (Cmax 0.761 ± 0.051 ng/mL; Tmax 8 h†) compared with plain
budesonide (Cmax 1.374 ± 0.104 ng/mL; Tmax 1 h†), while simulated colonic
tissue concentration increased approximately 5.5-fold. Disease Activity Index,
MPO, TNF-α, IL-1β, IL-6, oxidative-stress indices and histopathological damage
were markedly improved in the optimized-treatment group†. Simulated
corticosterone suppression decreased from 41.2% with plain budesonide to
11.4% with the optimized formulation. After 6 months at 40°C/75% RH, assay
remained 97.88% and the dissolution profile remained similar to initial testing
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(f2 ≈ 86.1)†.
Conclusion: The multi-trigger system provides a mechanistically coherent
approach to preferential colonic budesonide delivery. Integration of pH
protection, microbiota-responsive polysaccharides and time-dependent matrix
control has the potential to increase local therapeutic exposure while reducing
systemic corticosteroid burden.