Release kinetics of hydroxypropyl methylcellulose governing drug release and hydrodynamic changes of matrix tablet

BACKGROUND

Hydrophilic hydroxypropyl methylcellulose (HPMC) matrix tablets are the standard role model of the oral controlled-release formulation. Nevertheless, the HPMC kinetics for the mechanistic understanding of drug release and hydrodynamic behaviors are rarely investigated. This study aims to investigate the release behaviors of both HPMC and paracetamol (model drug) from the hydrophilic matrix tablet.

METHODS

Two different viscosity grades of HPMC were used (Low viscosity: 6 cps, High viscosity: 4,000 cps). Three different ratios of drug/HPMC (H:38.08%, M:22.85%, and L:15.23% (w/w) of HPMC amounts in total weight) matrix tablets were prepared by wet granulation technique. The release profiles of the drug and HPMC in a matrix tablet were quantitatively analyzed by HPLC and 1H-nuclear magnetic resonance (NMR) spectroscopy. The hydrodynamic changes of HPMC were determined by the gravimetric behaviors such as swelling and erosion rates, gel layer thickness, front movement data,and distributive near-infrared (NIR) chemical imaging of HPMC in a matrix tablet during the dissolution process.

RESULTS

High viscosity HPMC tablets showed slower release of HPMC than the release rate of drug, suggesting that drug release preceded polymer release.Different hydration phenomenon was qualitatively identified and corresponded to the release profiles. The release behaviors of HPMC and drug in the tablet could be distinguished with the significant difference with fitted dissolution kinetics model (Low viscosity HPMC 6cps; Korsmeyer-Peppas model, High viscosity HPMC 4000cps; Hopfenberg model, Paracetamol; Weibull model) according to the weight of ingredients and types of HPMC.

CONCLUSION

The determination of HPMC polymer release correlating with drug release, hydrodynamic behavior, and NIR chemical imaging of HPMC can provide new insights into the drug release-modulating mechanism in the hydrophilic matrix system.

Mechanistic understanding of salt-induced drug encapsulation in nanosuspension via acid-base neutralization as a nanonization platform technology to enhance dissolution rate of pH-dependent poorly water-soluble drugs

An acid-base neutralization technique has generated interest for the ability to achieve an enhanced dissolution of pH-dependent weakly basic or acidic poorly water-soluble drugs. However, the underlying nanonization mechanism, following acid-base neutralization, requires further elucidation. We hypothesized that the nanosuspensions (NSPs) via nanonization of drug particles could be attributed to the "salt-induced effect" and surfactant-driven micellization after acid-base neutralization. Rebamipide (RBM) and valsartan (VAL) were chosen as model drugs owing to poor water solubility and pH-dependent aqueous solubility. The drug NSP was rapidly obtained via salt formation (NaCl) after neutralization of the drug in basic NaOH solution and poloxamer 407 (POX 407) in acidic HCl solution. The NSP surrounded by NaCl salt was further stabilized by POX 407. The resulting NaCl salt modulated the critical micelle aggregation of POX 407, stabilizing the drug-loaded NSP in a cage of salt and micellar surfactant. In non-assisted homogenization, size analysis indicated the relationship between salt concentration and size reduction. Fourier transform infrared (FTIR) spectra revealed that the existence of hydrogen bonding between the drug and surfactant after neutralization, attributed to NSP size reduction. Changes in drug crystallinity to the nano-amorphous state were confirmed by powder X-ray diffraction (PXRD). Overall, the salt-induced drug NSP synergistically enhanced the dissolution rate, narrowing a gap between drug dissolution profiles in different pH environments.