The influence of thermal treatment and type of insoluble poly(meth)acrylates on dissolution behavior of very soluble drug from hypromellose matrix tablets evaluated by multivariate data analysis

Towards a better understanding of thermally treated polycarbophil matrix tablets for controlled release

Polycarbophil (POL), a polyacrylic acid cross-linked with divinyl glycol, is widely used in semisolid and solid dosage forms. When undergoing a thermal treatment in the range 120–160 °C, POL shows interesting morphological modifications, related to changes in physical properties, such as swelling of the powder granules, or hardening and matrix formation if included in the composition of a tablet. Thermal analysis conducted on POL highlighted a thermal event (Z) that can be correlated both to the shrinking of the powder granules and to the matrix formation in compacted POL powder. Modulated differential scanning calorimetry (MDSC) allowed to distinguish, inside event Z, an irreversible process overlapping with a reversible glass transition, attributable to the volatilization of residual solvents identified, through a complex TGA-FTIR-GC–MS interface, as acetate esters used for the polymer production as very fine powder. A specific interaction between acetates and POL, capable of stabilizing the polymer chains in a given conformation, was highlighted. The molecular rearrangement of the POL chains, following the volatilization of the solvent-stabilizers, is therefore ascribable to a loss of energetic stability of this material, which justifies the shrinking phenomena in the granules of the powder and the matrix formation when POL is compacted.

Chemometrics: a complementary tool to guide the isolation of pharmacologically active natural products

Chemometrics offers an important complementary tool to enhance the searching and isolation of bioactive natural products from natural sources.

Formulation of sustained release bioadhesive minitablets containing solid dispersion of levofloxacin for once daily ocular use

This study aimed to increase ocular residence time of levofloxacin by formulation into zero-order sustained release mucoadhesive minitablets for once daily administration using a hydrophobic-hydrophilic polymeric matrix. Levofloxacin was first formulated into solid dispersion with different ratios of Eudragit^® RS then the resulting solid dispersion was mixed with different concentrations of Carbopol^® and other excipients to be finally compressed into minitablets. A 2⁴ full factorial design was employed to estimate the effects and interactions of two formulation factors, and to establish their relationships with selected responses in the developed minitablets. The studied factors were: drug to Eudragit^® RS ratio, and percent of Carbopol^® in the minitablets. Sixteen ocular minitablets formulations were prepared and evaluated for the cumulative percentages drug release at 6, 12, and 24 h, as well as mucoadhesion time, mucoadhesive strength, and swelling index as response variables. After optimizing the responses, the optimized formulation was found to be stable on sterilization using gamma-irradiation and storage at 40 °C/75% RH for six months. In vivo testing of the optimized formulation showed that the minitablets extended levofloxacin release up to 24 h without causing any ocular irritation. The optimized formulation exhibited superior microbiological activity compared to the commercial product.

Highly Soluble Drugs Directly Granulated by Water Dispersions of Insoluble Eudragit® Polymers as a Part of Hypromellose K100M Matrix Systems

The aim of the present study was to investigate the suitability of insoluble Eudragit® water dispersions (NE, NM, RL, and RS) for direct high-shear granulation of very soluble levetiracetam in order to decrease its burst effect from HPMC K100M matrices. The process characteristics, ss-NMR analysis, in vitro dissolution behavior, drug release mechanism and kinetics, texture profile analysis of the gel layer, and PCA analysis were explored. An application of water dispersions directly on levetiracetam was feasible only in a multistep process. All prepared formulations exhibited a 12-hour sustained release profile characterized by a reduced burst effect in a concentration-dependent manner. No effect on swelling extent of HPMC K100M was observed in the presence of Eudragit®. Contrary, higher rigidity of formed gel layer was observed using combination of HPMC and Eudragit®. Not only the type and concentration of Eudragit®, but also the presence of the surfactant in water dispersions played a key role in the dissolution characteristics. The dissolution profile close to zero-order kinetic was achieved from the sample containing levetiracetam directly granulated by the water dispersion of Eudragit® NE (5% of solid polymer per tablet) with a relatively high amount of surfactant nonoxynol 100 (1.5%). The initial burst release of drug was reduced to 8.04% in 30 min (a 64.2% decrease) while the total amount of the released drug was retained (97.02%).

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.

Investigation of Dissolution Behavior HPMC/Eudragit®/Magnesium Aluminometasilicate Oral Matrices Based on NMR Solid-State Spectroscopy and Dynamic Characteristics of Gel Layer

Burst drug release is often considered a negative phenomenon resulting in unexpected toxicity or tissue irritation. Optimal release of a highly soluble active pharmaceutical ingredient (API) from hypromellose (HPMC) matrices is technologically impossible; therefore, a combination of polymers is required for burst effect reduction. Promising variant could be seen in combination of HPMC and insoluble Eudragits^® as water dispersions. These can be applied only on API/insoluble filler mixture as over-wetting prevention. The main hurdle is a limited water absorption capacity (WAC) of filler. Therefore, the object of this study was to investigate the dissolution behavior of levetiracetam from HPMC/Eudragit^®NE matrices using magnesium aluminometasilicate (Neusilin^® US2) as filler with excellent WAC. Part of this study was also to assess influence of thermal treatment on quality parameters of matrices. The use of Neusilin^® allowed the application of Eudragit^® dispersion to API/Neusilin^® mixture in one step during high-shear wet granulation. HPMC was added extragranularly. Obtained matrices were investigated for qualitative characteristics, NMR solid-state spectroscopy (ssNMR), gel layer dynamic parameters, SEM, and principal component analysis (PCA). Decrease in burst effect (max. of 33.6%) and dissolution rate, increase in fitting to zero-order kinetics, and paradoxical reduction in gel layer thickness were observed with rising Eudragit^® NE concentration. The explanation was done by ssNMR, which clearly showed a significant reduction of the API particle size (150-500 nm) in granules as effect of surfactant present in dispersion in dependence on Eudragit^®NE amount. This change in API particle size resulted in a significantly larger interface between these two entities. Based on ANOVA and PCA, thermal treatment was not revealed as a useful procedure for this system.