A formulation approach for development of HPMC-based sustained release tablets for tolterodine tartrate with a low release variation

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.

Formulation optimization and in vitro characterization of granisetron-loaded polylactic-co-glycolic acid microspheres prepared by a dropping-in-liquid emulsification technique

PURPOSE

Traditional dosage forms of granisetron (GRN) decrease patient compliance associated with repeated drug administration because of the short half-life of the drug.

METHODS

In this study, novel GRN-loaded polylactic-co-glycolic acid (PLGA) sustained release microspheres were prepared for the first time via a dropping-in-liquid emulsification technique. The effect of various factors, such as pH of the outer phase, Tween80, polyvinyl alcohol (PVA) concentrations, and hardening process, on the encapsulation efficiency (EE), drug loading (DL), and particle size of microspheres were extensively studied. The physicochemical properties, including drug release, surface morphology, crystallinity, thermal changes, and molecular interactions, were also studied.

RESULTS

GRN has a pH-dependent solubility and showed a remarkably high solubility under an acidic condition. The EE of the alkaline medium (pH 8) was higher than that of the acidic medium (pH 4.0). EE and DL decreased in the presence of Tween80 in the outer phase, whereas EE significantly increased during hardening. The particle size of microspheres was not affected by PVA and Tween80 concentrations, but it was influenced by PVA volume and hardening. X-ray diffraction and differential scanning calorimetry results showed that the physical state of the drug changed from a crystalline form to an amorphous form, thereby confirming that the drug was encapsulated into the PLGA matrix. Fourier transform-infrared spectroscopy confirmed that some molecular interactions occurred between the drug and the polymer. GRN-loaded PLGA microspheres showed sustained release profiles of over 90% on week 3.

CONCLUSION

GRN-loaded PLGA microspheres with sustained release were successfully prepared, and they exhibited a relatively high EE without Tween 80 as an emulsifier and with hardening process.

Evaluation of the impact of abuse deterring agents on the physicochemical factors of tramadol-loaded tablet and the definition of new abuse deterrent index

In the design of abuse-deterrent formulations (ADFs), pharmaceutical strategies that do not modify the physical and chemical properties of opioid dosage forms should be investigated. Among these, four major drug abusing factors, including particle size by physical modification, swellability, dissolution rate, and solvent extraction, were mainly characterized for evaluating abuse deterrence of narcotics. Tramadol hydrochloride (TMD) was chosen as a model drug. In this study, the frequently used eight generally recognized as safe (GRAS)-listed pharmaceutical excipients, including polyvinyl alcohol (PVA), hydroxypropyl methylcellulose (HPMC 4,000, HPMC 100,000), xanthan gum (XG), cellulose acetate (CA), polyethylene oxide (PEO), carbomer 940 NF, and Compritol® 888 ATO, were selected as abuse deterring agents and used to prepare TMD-loaded tablet. A new abuse-deterrent index (ADI) for compressed TMD-loaded tablets was originally defined and considered as an index of drug abuse deterrence, based on the assumption that it was proportional to particle size and swellability but inversely proportional to dissolution and solvent extraction rates after assigning the categorized five scale scores (one to five) to the four experimental data. The resulting ADI of the selected eight abuse deterring agents in deionized water was given in decreasing order: HPMC 4000 > carbomer 940 > Compritol® 888 ATO > XG > PVA > HPMC 100,000 > PEO, and CA while in 40% hydro-alcoholic solution in the decreasing order: carbomer 940 > HPMC 4,000 ≒ XG > PVA > HPMC 100,000 > PEO > Compritol® 888 ATO > CA. Interestingly, the HPMC 4,000 and carbomer 940 showed the highest ADI and gave drug abuse deterrent potential. This study could provide a pharmaceutical strategy that utilizes a variety of abuse-deterring agents and resist to extraction solvents in designing drug abuse-deterrent formulations and establishing their standard guidelines for regulatory authorities.

Multivariate analysis as a method to understand variability in a complex excipient, and its contribution to formulation performance

A key part of the Risk Assessment of excipients is to understand how raw material variability could (or does) contribute to differences in performance of the drug product. Here we demonstrate an approach which achieves the necessary understanding for a complex, functional, excipient. Multivariate analysis (MVA) of the certificates of analysis of an ethylcellulose aqueous dispersion (Surelease) formulation revealed low overall variability of the properties of the systems. Review of the scores plot to highlight batches manufactured using the same ethylcellulose raw material in the formulation, indicated that these batches tend to be more closely related than other randomly selected batches. This variability could result in potential differences in the quality of drug product lots made from these batches. Manufacture of a model drug product from Surelease batches coated using different lots of starting material revealed small differences in the release of a model drug, which could be detected by certain model dependent dissolution modeling techniques, but they were not observed when using model-independent techniques. This illustrates that the techniques are suitable for detecting and understanding excipient variability, but that, in this case, the product was still robust.

Continuous twin screw granulation of controlled release formulations with various HPMC grades

HPMC is a popular matrix former to formulate tablets with extended drug release. Tablets with HPMC are preferentially produced by direct compression. However, granulation is often required prior to tableting to overcome poor flowability of the formulation. While continuous twin screw granulation has been extensively evaluated for granulation of immediate release formulations, twin screw granulation of controlled release formulations including the dissolution behavior of the formulations received little attention. Therefore, the influence of the HPMC grade (viscosity and substitution degree) and the particle size of theophylline on critical quality attributes of granules (continuously produced via twin screw granulation) and tablets was investigated in the current study. Formulations with 20 or 40% HPMC, 20% theophylline and lactose were granulated with water at fixed process parameters via twin screw granulation. The torque was influenced by the viscosity and substitution degree of HPMC, but was not a limiting factor for the granulation process. An optimal L/S ratio was selected for each formulation based on the granule size distribution. The granule size distributions were influenced by the substitution degree and concentration of HPMC and the particle size of theophylline. Raman and UV spectroscopic analysis on 8 sieve fractions of granules indicated an inhomogeneous distribution of theophylline over the size fractions. However, this phenomenon was not correlated with the hydration rate or viscosity of HPMC. Controlled release of theophylline could be obtained over 24h with release profiles close to zero-order. The release of theophylline could be tailored via selection of the substitution degree and viscosity of HPMC.