Rheology of polyol behenates and drug release from matrix monolithic capsules

Formulation, Characterization and Comparative Pharmacokinetic Study of Bupropion Floating Raft System as a Promising Approach for Treating Depression

The aim of this study was to formulate, evaluate, and compare satiety-enhancing floating raft system (FRS) of bupropion as gastroretentive drug delivery systems (GRDDS) using in-situ gelling pectin and alginate. Bupropion was considered as a good candidate for such systems due to high water solubility that requires frequent dosing. Pectin and alginate could prolong satiety sensation augmenting weight loss of bupropion. A 2⁴ full factorial design was tailored to inspect the effect of the response variables (gel-forming polymer type, calcium carbonate percentage, glyceride lipid type and percentage). Gelation lag time, floating lag time, as well as drug released percent after 1 and 8 h were selected as dependent variables. The optimal system was investigated for compatibility and bioavailability study in healthy human volunteers relative to marketed Wellbutrin® sustained release tablets. The optimal FRS (3% alginate, 2% precirol®, and 2% CaCO₃) was selected. This system had an optimum viscosity that will allow a rapid sol-gel transformation in the stomach, excellent floating behavior, and controlled release profile with a comparable bioavailability. The optimal FRS would be a novel liquid GRDDS in controlling bupropion rate release especially for depression associated with eating disorders or dysphagia improving patient compliance and drug efficacy.

Formulation, release characteristics, and bioavailability study of gastroretentive floating matrix tablet and floating raft system of Mebeverine HCl

To prolong the residence time of dosage forms within the gastrointestinal tract until all drug is released at the desired rate is one of the real challenges for oral controlled-release drug delivery systems. This study was designed to develop a controlled-release floating matrix tablet and floating raft system of Mebeverine HCl (MbH) and evaluate different excipients for their floating behavior and in vitro controlled-release profiles. Oral pharmacokinetics of the optimum matrix tablet, raft system formula, and marketed Duspatalin^® 200 mg retard as reference were studied in beagle dogs. The optimized tablet formula (FT-10) and raft system formula (FRS-11) were found to float within 34±5 sec and 15±7 sec, respectively, and both remain buoyant over a period of 12 h in simulated gastric fluid. FT-10 (Compritol/HPMC K100M 1:1) showed the slowest drug release among all prepared tablet formulations, releasing about 80.2% of MbH over 8 h. In contrast, FRS-11 (Sodium alginate 3%/HPMC K100M 1%/Precirol 2%) had the greatest retardation, providing sustained release of 82.1% within 8 h. Compared with the marketed MbH product, the C_max of FT-10 was almost the same, while FRS-11 maximum concentration was higher. The t_max was 3.33, 2.167, and 3.0 h for marketed MbH product, FT-10, and FRS-11, respectively. In addition, the oral bioavailability experiment showed that the relative bioavailability of the MbH was 104.76 and 116.01% after oral administration of FT-10 and FRS-11, respectively, compared to marketed product. These results demonstrated that both controlled-released floating matrix tablet and raft system would be promising gastroretentive delivery systems for prolonging drug action.

Development of gastroretentive metronidazole floating raft system for targeting Helicobacter pylori

The study demonstrates the feasibility of prolonging gastric residence time and release rate of metronidazole (Mz) by preparing floating raft system (FRS) using ion-sensitive in situ gel forming polymers. FRSs contained 3, 4, 5 and 0.5, 0.75, 1% w/v sodium alginate (Alg) and gellan gum (G), respectively, 0.25% w/v sodium citrate and calcium carbonate (C). Lipids: glyceryl mono stearate (GMS), Precirol(®) and Compritol(®) were incorporated into G-based formulations (G1%C1%). Mz:lipid ratio was 1:1, except for Mz:GMS, ratios of 1:1.5 and 1:2 were also investigated. Buoyancy, gelation capacity and viscosity parameters were evaluated. Drug release and kinetics for selected formulae were examined. The selected lipid containing formula was subjected to an accelerated stability testing. Alg4%C2% FRS exhibited short gelation lag time (3s), long duration (>24h), floating lag time 1m in and duration >24h, and a reliable sustained drug release (MDT 6h). Gellan gum FRSs achieved successful floating gastroretention, but failed to achieve the required gelation capacity. Incorporation of GMS (Mz:GMS 1:1) enhanced the gelation lag time and duration (6s and >24h, respectively), keeping sustained drug release and formulation stability. The improved characteristics of the selected FRS make them excellent candidates for gastric targeting to eradicate Helicobacter pylori.

Development of novel sustained release matrix pellets of betahistine dihydrochloride: effect of lipophilic surfactants and co-surfactants

Sustained release matrix pellets of the freely water soluble drug, betahistine dihydrochloride (BH), were prepared using freeze pelletization technique. Different waxes and lipids (cetyl alcohol, beeswax, glyceryl tripalmitate (GTP) and glyceryl tristearate) were evaluated for the preparation of matrix pellets. A D-optimal design was employed for the optimization and to explore the effect of drug loading (X(1)), concentration of lipophilic surfactant (X(2)), concentration of co-surfactant (X(3)) and wax type (X(4)) on the release extent of the drug from matrix pellets. The entrapment efficiency (Y(1)), pellet diameter (Y(2)), and the percentage drug released at given times were selected as dependent variables. Results revealed a significant impact of all independent variables on drug release from the formulated pellets. The lipophilic surfactant significantly increased both the entrapment efficiency and the in vitro drug release and significantly decreased the pellet size. The optimized BH-loaded pellets were composed of 19.95% drug loading, 9.95% Span(®) 80 (surfactant), 0.25% Capmul(®) (co-surfactant) using glyceryl tripalmitate as a matrix former. The release profiles of the drug from hard gelatin capsule containing optimized pellets equivalent to 32 mg BH was similar to that of target release model for once-daily administration based on similarity factor. It could be concluded that a promising once-daily capsule containing sustained release pellets of BH was successfully designed.

Theophylline-loaded compritol microspheres prepared by ultrasound-assisted atomization

Nine solid dispersions were prepared by the melting method in the form of particles containing theophylline at 10%, 20%, and 30% (w/w) in three Compritols (Compritol 888 ATO, HD5 ATO, E ATO) to compare their efficiency in controlling theophylline release. After solidification the mass was ground and granules were evaluated by thermal [differential scanning calorimetry, hot stage microscopy (HSM)] and spectroscopic [Fourier transform infrared (FTIR), Raman, X-ray powder diffraction (XRD)] analysis and the solubility parameters. Another nine samples of the same composition were obtained as microspheres by ultrasound-assisted (US) atomization. XRD confirmed the presence of crystalline theophylline inside the solid dispersions. FTIR and Raman microspectroscopy revealed that crystals of the drug were present on the granule surface. On the contrary, the surface of the final microspheres did not present free drug crystals. The granules do not work so efficiently as microspheres in controlling the release of theophylline: 888 ATO ≈ HD5 ATO > E ATO represents the order of the ability of the Compritols to control the theophylline release from microspheres. HSM revealed that, on aging, the dissolved drug crystallizes, considerably modifying the granule formulation and that US vibration, speeding up the crystallization of the drug during the preparation of microspheres, greatly reduces the changes associated with aging.

Influence of poloxamers on the dissolution performance and stability of controlled-release formulations containing Precirol ATO 5

Lipid excipients are usually used for the development of sustained-release formulations. When used in relatively high quantities, Precirol ATO 5 imparts sustained-release properties to solid oral dosage forms, by forming a lipid matrix. To control or adjust the drug release kinetics from such lipid matrix however, one must often resort to complementary ingredients or techniques. This study investigates the influence of poloxamers (Lutrol) included in lipid matrices composed of glyceryl palmitostearate (Precirol ATO 5) on their dissolution performance and their stability. The addition of these hydrophilic polymers in the lipid matrix increased the amount of theophylline released thanks to the swelling of the hydrophilic polymer and the creation of a porous network into the inert lipid matrix. The grade and the quantity of Lutrol could modulate the extent of drug release. Theophylline was released mainly by the matrix erosion but also by diffusion through the pores as suggested by the Peppas' model. Moreover, the addition of Lutrol enhanced the stability during storage. The theophylline release was quite steady after 6 months in different conditions (temperature and humidity). Thus, the mixture of glyceryl palmitostearate and poloxamers is an approach with many advantages for the development of controlled-release formulations by capsule molding.

Study of In‐Vitro Release Characteristics of Carbamazepine Extended Release Semisolid Matrix Filled Capsules Based on Gelucires

Various extended release carbamazepine (CBZ) formulations have been developed previously, in order to reduce the frequency of dosing in chronic therapy and to decrease the variability in drug plasma concentration. In the present study, the suitability of different grades of Gelucires (G, glyceride based excipients) to formulate CBZ extended release capsules by the application of semisolid matrix (SSM) filling capsule technology was investigated. The possible modification of CBZ release kinetics by using Gelucire blends or inclusion of hydrophilic additives in the SSM was studied. The effect of ageing on some selected formulations was also evaluated, using scanning electron microscopy and differential thermal analysis. Twenty-one capsule formulations were prepared and assessed for their release characteristics. The mechanism of drug release from the test formulations was studied. The following results were obtained: a) Release data could not be correlated to the melting point (mp) of Gelucires used, pointing to relative lipophilicity of the base as a more important determinant of drug release. Among Gelucire grades having melting points higher than 37 degrees C, the release rate proved to be highly dependent on the HLB value and matrix composition. b) CBZ release occurred by different mechanisms, including matrix disintegration, diffusion and or erosion depending on the vehicle employed. c) Zero order release profiles of CBZ were obtained from SSM-based on G50/13, G53/10 and their blends in ratios higher than 1:1 and G53/10 containing croscarmellose sodium. d) The ageing study revealed that these latter formulations, except those based on G50/13, also showed high dissolution stability during one year of shelf ageing. e) PVP, as a polymorphic transformation inhibitor, can be used to reduce the storage-induced changes of some grades of Gelucires. From the above data, it can be concluded that different grades of Gelucires and their blends as well as hydrophilic additives could be successfully used to formulate CBZ extended release SSM filled capsules with various release kinetics.

Aplicação de um Modelo Reológico Não-Linear em Sistemas Poliméricos Dilatantes

A dilatância é um comportamento reológico comum a vários sistemas poliméricos embora não ocorra em polímeros puros. Existem várias teorias aplicáveis à explicação desse fenômeno e alguns modelos matemáticos para o ajuste de dados experimentais de quatro de suas seis formas de ocorrência. Neste trabalho é dado enfoque à dilatância antecedida por um comportamento newtoniano e sucedida pelo comportamento pseudoplástico. Para ajustar dados constantes da literatura para sistemas desse tipo, é apresentado um modelo híbrido e não-linear. Para o teste do modelo foram utilizados dados existentes na literatura para solução de alfa,ômega poli(t-butilestireno) em óleo mineral e suspensão de partículas do copolímero de estireno com acrilato de metila em solução aquosa de poli(ácido acrílico). O modelo proposto apresenta boa concordância com os dados experimentais.

Rheological behavior of drug suspensions in Gelucire mixtures and proxyphylline release from matrix hard gelatin capsules

Mixtures of Gelucires 50/02 and 50/13 showing different hydrophilic-lipophilic balances (HLB) and of proxyphylline were used to prepare suspensions at a concentration of 25% and to manufacture extended release hard gelatin capsules by cooling. The rheological behaviors of Gelucire mixtures with and without drug were determined by adjustment of the rheograms to the Ostwald power-law and by statistical assessment of the flow index. Pure Gelucire mixtures were very slightly shear thickening whereas proxyphylline suspensions had a thixotropic shear thinning behavior. These rheological behaviors can be explained by the chemical composition and by the ratio of the two Gelucires used. Extended release of proxyphylline was obtained with all these mixtures. Drug release increased with Gelucire mixture HLB owing to higher erosion. A viscosity-release relationship was found and allowed, with these two Gelucires of extreme HLB and viscosities, to define the formulations which will give an optimal drug release, by the determination of their suspension viscosity. Modeling of dissolution kinetics has generally shown the predominance of surface erosion of the plugs relative to drug diffusion inside the matrix. This was confirmed by the better linearization of percentage released, according to Hixson-Crowell as compared with Higuchi.