Development of enteric-coated osmotic tablet for colon-targeted hydrocortisone delivery

Abstract

Purpose: To formulate enteric-coated osmotic tablets for colon-targeted delivery of hydrocortisone.

Methods: Nine core tablet batches were prepared with varying amounts of potassium chloride (osmogen), polyethylene glycol 4000 (solubilizing agent), starch (wicking agent), and microcrystalline cellulose (binder). The core tablets, each containing 20 mg hydrocortisone, were coated sequentially with a cellulose acetate (semi-permeable) membrane and Eudragit S-12,5-P/PEG 400 (enteric polymer) system. In vitro dissolution was assessed over a period of twelve hours across physiologically relevant pH conditions.

Results: The enteric coating suppressed drug release to approximately 3 % during the initial two hours (pH 1.2), with only 3.4 – 5.1 % cumulative release after four hours at pH 4.5. Substantial release was initiated at pH 7.2, with the majority of hydrocortisone released during the final six-hour phase. Formulations B6 (containing 20 % osmogen and 1.67 % binder) and B7 (containing 13.33 % osmogen and 8.33 % binder) exhibited optimal colon-targeting, achieving 95.20 % and 95.30 % total release respectively. Release kinetics were predominantly first-order, with transport governed by non-Fickian (anomalous) diffusion.

Introduction

Targeted-delivery systems aim to release the active ingredient at a specific site, thereby enhancing therapeutic efficacy and minimizing systemic side effects [1]. Despite its advantages, oral delivery for colon targeting faces multiple physiological barriers in the gastrointestinal tract, including pH variability, acid and enzymatic degradations, and variable transit times [2,3]. Strategies developed to overcome these barriers include pH-dependent systems, time-controlled systems, pressure-controlled systems, coating, prodrug approaches, and microflora-activated systems [4].

Osmotically controlled drug delivery systems (OCDDS) represent an advanced form of time-controlled release, in which drug liberation is driven by osmotic pressure gradients. Such systems can be adapted for colon targeting, particularly when combined with pH-sensitive enteric coatings such as Eudragit E100 [5]. Typical OCDDS components include the active drug, a solubilizing agent, a wicking agent, an osmogen, a semi-permeable membrane polymer, a pore former, a plasticizer and a coating solvent system [6].

Inflammatory bowel diseases (IBDs) are commonly treated with anti-inflammatory agents, corticosteroids, and antibiotics. Conventional oral corticosteroids are suboptimal for colon-specific therapy because they release the drug before reaching the target site, limiting local efficacy [7]. Rectal formulations, while capable of localized delivery, often fail to reach the proximal colon and are associated with poor patient compliance due to discomfort [8]. A colon-targeted system capable of protecting the drug during transit through the upper gastrointestinal tract and releasing it only upon arrival in the colon is therefore highly desirable for the management of colon disorders [9].

Hydrocortisone, a corticosteroid widely used in IBD therapy, exerts both immunosuppressive and anti-inflammatory effects [10]. Its mechanism of action involves inhibition of phospholipase A₂, preventing phospholipid hydrolysis and subsequent synthesis of pro-inflammatory cytokines [11]. The action underlies its capacity to induce rapid clinical remission of inflammation [12]. This present study was designed to develop an osmotically controlled, pH-regulated, colon-targeted hydrocortisone tablet for the effective management of inflammatory bowel diseases.

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Materials

Hydrocortisone powder was purchased from Dotcom Pharma, India. The chemicals used for the study include solid polyethylene glycol 4000 (Central Drug House, India), liquid polyethylene glycol 400 (Central Drug House, India), Eudragit S-12 and Eudragit 5-P (Evonic Industries, Germany), pectin and potassium chloride (Merck, Germany), cellulose acetate, starch, titanium dioxide, orange colour powder and microcrystalline cellulose (BDH Chemicals, England), magnesium stearate and talc (Hopkin ad Williams Ltd., England), isopropyl alcohol and ethanol (Halewood Chemicals Ltd., England).

Table 1: Composition of the various hydrocortisone core tablet formulations

Ebiekpi, G., Otakagu, E., Femi-Oyewo, M., Majekodunmi, S., Uduk, E., & Olorunsola, E. (2026). Development of enteric-coated osmotic tablet for colon-targeted hydrocortisone delivery. Tropical Journal of Pharmaceutical Research, 25(5), 619–626. https://doi.org/10.4314/tjpr.v25i5.3