Effect of Diluents on the Drug Release ofControlled-Release Matrix Tablets of BCSClass I Drugs
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Abstract
This study aimed to assess the influence of soluble and insoluble diluents on drug release from the
controlled-release (CR) matrix tablets of Biopharmaceutics Classification System (BCS) Class I drugs prepared
with hydrophilic polymers. Methods: Tramadol hydrochloride (TDL HCl) and venlafaxine hydrochloride (VFX
HCl)-CR matrix tablets (CR) were prepared with polymers of hydrophilic nature (Kollidon SR and xanthan
gum) with and without diluents (insoluble and soluble, such as dicalcium phosphate, microcrystalline cellulose,
lactose monohydrate, and mannitol). Pre-compression and post-compression parameters were evaluated for these
CR tablets. In vitro drug release kinetics were evaluated using zero-order, first-order, and the mechanism was
evaluated employing Higuchi, Peppas, and Hixson–Crowell. Model-independent parameters such as T50, T75,
mean dissolution time (MDT)50, MDT75, f1, and f2 comparison were also performed. These model-dependent
and model-independent methods were used to compare in vitro drug release between the formulations prepared
with and without diluents. Results and Conclusion: The first order release was followed by all the formulations.
The drug release in many cases followed an erosion mechanism in addition to the Higuchi diffusion mechanism
from these tablets. The correlation coefficient values of these mechanisms are close to each other. The primary
observation was that the presence of insoluble diluents (dicalcium phosphate and microcrystalline cellulose) in
the hydrophilic matrix of VFX HCl tablets retarded the drug release significantly. However, water-soluble diluents
(lactose monohydrate and mannitol) enhanced the drug release when incorporated in the hydrophilic matrix of
VFX HCl with synthetic polymer (Kollidon SR) only, and did not affect the release when the natural polymer
(xanthan gum) was used. Diluents did not influence drug release in the case of the TDL HCl formulation prepared
with hydrophilic polymers.
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