Release mechanisms behind polysaccharides-based famotidine controlled release matrix tablets

DDSolver Software Application for Quantitative Analysis of In Vitro Drug Release Behavior of the Gastroretentive Floating Tablets Combined with Radiological Study in Rabbits

Background:

Gastroretentive drug delivery systems (GRDDSs) are designed to release the drug in the stomach over a prolonged time; thus, they can reduce drug dosing frequency and dose size and improve patient compliance. GRDDSs are also highly effective in enhancing the bioavailability of the drug that exhibits window absorption in specific segments of the gastrointestinal (GI) tract. Famotidine (FMT), an H2 receptor antagonist, is an example of these drugs. FMT is a slightly water-soluble drug but well soluble in an acidic medium. This research aims to formulate FMT gastro-retentive floating tablets (FMT-GRFTs) to improve the bioavailability and therapeutic activity of the drug and increase patients' adherence to treatment. In addition, the in vitro release behavior of the prepared FMT-GRFTs was quantitatively analyzed using the DDSolver software to assist in selecting the successful formulation that was then evaluated in vivo.

Methods:

The direct compression technique prepared numerous tablet formulations and was subjected to the pre-and post-compression evaluation. Data of FMT dissolution in the simulated gastric medium was analyzed by various kinetic models built in the DDSolver program. In addition, the simulated pharmacokinetics (AUC, MDT, and MRT), R2 adjusted, AIC, MSC, correlation of the residuals, and similarity factor (f2) were also generated.

Results:

The results revealed that FMT release from the candidate formula (FH3) fitted to the first-order kinetic model, with a high value of R2 adjusted and MSC and a low AIC. The release behavior exhibited the Fickian diffusion mechanism. The similarity factor showed no significant difference (p < 0.05) of the test sample compared to the reference product. Nevertheless, the simulated pharmacokinetic parameter, AUC, proved a two-fold enhancement in FMT bioavailability, with a significant increment in the MDT and MRT compared with the reference product. The FT-IR spectroscopy analysis indicated the absence of drug-excipients/polymer interaction. The in vivo X-ray studies on rabbits confirmed that the floating tablets showed nearly eight hours of gastric residence.

Conclusion:

DDSolver software was helpful in deciding the optimized formulation of FMT floating tablets. The radiological examination in rabbits for gastric retention was consistent with the release data analysis in vitro.

Thermosensitive Bioadhesive Hydrogels Based on Poly(N-isopropylacrilamide) and Poly(methyl vinyl ether-alt-maleic anhydride) for the Controlled Release of Metronidazole in the Vaginal Environment

The development of thermosensitive bioadhesive hydrogels as multifunctional platforms for the controlled delivery of microbicides is a valuable contribution for the in situ treatment of vagina infections. In this work, novel semi-interpenetrating network (s-IPN) hydrogels were prepared by the entrapment of linear poly(methyl vinyl ether-alt-maleic anhydride) (PVME-MA) chains within crosslinked 3D structures of poly(N-isopropylacrylamide) (PNIPAAm). The multifunctional platforms were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermal techniques, rheological analysis, swelling kinetic measurements, and bioadhesion tests on porcine skin. The hydrogels exhibited an interconnected porous structure with defined boundaries. An elastic, solid-like behavior was predominant in all formulations. The swelling kinetics were strongly dependent on temperature (25 °C and 37 °C) and pH (7.4 and 4.5) conditions. The s-IPN with the highest content of PVME-MA displayed a significantly higher detachment force (0.413 ± 0.014 N) than the rest of the systems. The metronidazole loading in the s-IPN improved its bioadhesiveness. In vitro experiments showed a sustained release of the antibiotic molecules from the s-IPN up to 48 h (94%) in a medium simulating vaginal fluid, at 37 °C. The thermosensitive and bioadhesive PNIPAAm/PVME-MA systems showed a promising performance for the controlled release of metronidazole in the vaginal environment.

In situ composite ion-triggered gellan gum gel incorporating amino methacrylate copolymer microparticles: a therapeutic modality for buccal applicability

The aim of the current investigation is to delineate the buccal applicability of an in situ composite gel containing aceclofenac (AC) amino methacrylate copolymer microparticles (MPs), surmounting limitations of oral existing conventional therapy. AC Eudragit RL100 MPs were fabricated and statistically optimized using 2²4¹ factorial design. Better buccal applicability and enhanced localization were achieved by combining the optimum MPs with in situ ion-activated gellan gum gel. The crosslinking and gelation of in situ gel were investigated by morphological and solid state characterizations. Suitability for buccal delivery and in vivo therapeutic efficacy in inflammation model of rats were also assessed. Results showed that the best performing formula displayed particle size (PS) of 51.00 µm and high entrapment efficiency (EE%) of 94.73%. MPs were successfully entrapped inside the gel network of the composite system. Gelation tendency, pH, shear-thinning properties and mucoadhesivity of the prepared in situ composite gel guaranteed its buccal suitability. Sustained AC release features and promising in vitro anti-arthritic response were also demonstrated. Moreover, consistent and prolonged in vivo anti-inflammatory effect was achieved, relative to standard AC. Taken together; this study proves the potential of in situ composite gel as an appropriate therapeutic proposal for AC buccal delivery.

Tablet formulation of Famotidine-loaded P-gp inhibiting nanoparticles using PLA-g-PEG grafted polymer

Our work aimed at evaluating the use of permeability glycoprotein (P-gp) inhibiting nanoparticles (NPs) as a part of a suitable oral solid dosage to improve bioavailability. Famotidine (Pepcid^®), a stomach acid production inhibitor, was used as a drug model to test our hypothesis. Famotidine-loaded NPs were prepared by solvent emulsion evaporation using PEG grafted on a polylactide acid (PLA) polymer backbone (PLA-g-PEG), with a 5% molar ratio of PEG versus lactic acid monomer and PEG of either 750 or 2000 Da molecular weight. Tablet formulation was composed of 40% Famotidine-loaded NPs, 52.5% microcrystalline cellulose as filler, 7% pre-gelatinized starch as binder/disintegrant, and 0.5% magnesium stearate as lubricant. Tablets containing 1.6 mg of Famotidine were prepared at an average weight of 500 mg, thickness of 6.2-6.5 mm, hardness of 5-8 kp, and disintegration time of <1 min. Our results suggest that Famotidine-loaded NPs using grafted PEG-g-PLA polymers can be formulated as an oral solid dosage form while effectively inhibiting P-gp mediated Famotidine efflux, irrespective of PEG molecular weights. This could therefore represent an attractive formulation alternative to enhance oral permeability and bioavailability of drugs that are P-gp substrates.

Design of PEG-grafted-PLA nanoparticles as oral permeability enhancer for P-gp substrate drug model Famotidine

Bioavailability of oral drugs can be limited by an intestinal excretion process mediated by P-glycoprotein (P-gp). Polyethylene glycol (PEG) is a known P-gp inhibitor. Dispersion of Famotidine (a P-gp substrate) within PEGylated nanoparticles (NPs) was used to improve its oral bioavailability. In this work, we evaluated the potential impact of NPs prepared from a grafted copolymer of polylactic acid and PEG on P-gp function by studying in vitro permeability of Famotidine across Caco-2 cells. Copolymers of PEG grafted on polylactic acid (PLA) backbone (PLA-g-PEG) were synthesised with 1 mol% and 5 mol% PEG vs. lactic acid monomer using PEG 750 and 2000 Da. The polymers were used to prepare Famotidine-loaded NPs and tested in vitro on Caco-2 cells. Significant decrease in basolateral-to-apical transport of Famotidine was observed when Famotidine was encapsulated in NPs prepared from PLA-g-PEG5%. NPs prepared from PLA-g-PEG5% are promising to improve oral bioavailability of P-gp substrates.

Release kinetics of highly porous floating tablets containing cilostazol

This study focuses on developing a highly porous floating tablet containing cilostazol. The underlying release mechanism of cilostazol from porous and floating tablets in dissolution media containing surfactants was investigated. The tablets were prepared by compressing granules and excipients with a sublimating agent, followed by sublimation under vacuum. The volatile material for the sublimating agent was chosen based on its flow properties using conventional methods as well as the twisted blade method. Resultant tablets could float immediately and had significantly higher tensile strengths than conventional tablets of similar porosities, holding a promising potential for increasing gastroretentive properties. Fitting the release profiles to the Korsmeyer-Peppas equation indicated Super Case II, Case II and non-Fickian kinetics, which implied that the release was affected by both floating behavior and matrix erosion. Abrupt changes in release kinetic parameters and erosional behaviors were found between the tablets containing different amounts of HPMC, indicating the existence of an excipient percolation threshold. Neither the surfactant in the media nor the porosity affected the dominant release mechanism, which was matrix erosion. Understanding the dominant release mechanism and percolation threshold allows for tuning the formulation to obtain various release profiles.

Formulation and in vitro evaluation of size expanding gastro-retentive systems of levofloxacin hemihydrate

Size increasing (plug-type) levofloxacin hemihydrate (LVF) tablets for eradication of Helicobacter pylori (H. pylori) were prepared using in situ gel forming polymers including: gellan gum, sodium alginate, pectin and xanthan gum. Effect of cross-linkers: calcium and aluminum chloride, on the drug release was also studied. The prepared tablets were evaluated for their physicochemical parameters: weight variation, thickness, friability, hardness, drug content, water uptake and in vitro drug release. The optimized formula was subjected to further studies such as radial swelling test, FT-IR and DSC. Results revealed that LVF release depends not only on the nature of the matrix but also on the type of cross linker used to form this polymeric matrix. The addition of either calcium chloride or aluminum chloride, as cross-linkers, to gellan gum formulations significantly decreased drug release. Other polymers' formulations resulted in increased drug release upon addition of the same cross-linkers. The formula containing xanthan gum without any cross linker showed the most sustained LVF release with an increase in diameter with time, thus acting as a plug-type dosage form. IR spectra and DSC thermograms of LVF, xanthan gum, and a physical mixture of both, indicated that there was no interaction between the drug and the polymer and confirmed the drug stability.

Nasal polysaccharides-glucose regulator microparticles: optimization, tolerability and antidiabetic activity in rats

The aim of the present study was to load the post-prandial glucose regulator, repaglinide (REP), on spray dried mucoadhesive microparticles (MPs) comprising anionic polysaccharides. The formulation parameters of the polysaccharides-REP spray dried powders (SDP) namely, polysaccharide type and drug to polymer (D/P) ratio, were optimized for % release after 5 min (R%5 min) and time required for 80% release (T80%). The suitability of the selected formulae for nasal application was evaluated by ex vivo mucoadhesion, in vitro cytocompatability and tolerability studies. A pharmacodynamic study in diabetic rats was conducted. Results showed that both polysaccharide type and amount greatly influenced the chosen responses. REP was highly incorporated in mucoadhesive MPs with proven safety on the rat nasal mucosa. The selected REP loaded powders exhibited a significant two to threefold increase in total decrease in blood glucose compared to the nasal and intravenous solutions.