Microsphere formulations of ambroxol hydrochloride: influence of Okra (Abelmoschus esculentus) mucilage as a sustained release polymer.

Ambroxol hydrochloride (AH), a secretion-releasing expectorant, is a good candidate for sustained delivery. Mucilages are biodegradable, inexpensive carriers in microsphere formulations. The study aimed to prepare microspheres of AH using Okra mucilage obtained from pods of Abelmoschus esculentus combined with sodium alginate at various polymer/drug ratios. Okra mucilage was characterized for morphology, swelling, viscosity and flow properties. AH microspheres were prepared by ionic emulsification method and characterized using size, entrapment efficiency, swelling index and dissolution time (t50). A full 2 by 3 factorial experimental design using three factors (Okra mucilage/alginate ratio X1; drug/polymer ratio X2; and polymer concentration X3), each at two levels, was used to determine the effects of formulation variables on the responses. Optimized formulations of AH microspheres had sizes ranging from 250.91 ± 16.22 to 462.10 ± 23.85 µm; swelling index 1.35 ± 0.05 and 3.20 ± 0.03 and entrapment 55.70 ± 3.55-94.11 ± 4.50%. The microspheres exhibited sustained release of AH over a prolonged period as revealed by the dissolution time (t50) 2.85 ± 1.03-7.50 ± 0.96 h. Drug release kinetics generally followed zero order, implying that the process is constant and independent of the initial concentration of drug. Polymer concentration had the highest influence on microsphere size, entrapment efficiency and dissolution time while Okra/alginate ratio had the highest influence on swelling. Okra mucilage was a suitable polymer that could serve as an alternative to synthetic polymers in sustaining the release of ambroxol hydrochloride.

Development of Theophylline Microbeads Using Pregelatinized Breadfruit Starch (Artocarpus altilis) as a Novel Co-polymer for Controlled Release.

Purpose: The aim of this study was to prepare formulations of theophylline microbeads using pregelatinized breadfruit starch (Artocarpus altilis, family Moraceae) in combination with sodium alginate and chitosan at various polymer: drug ratios. Microbead formulations for controlled delivery of theophylline would be better alternatives to conventional dosage forms for optimized drug therapy. Methods: The native and pregelatinized starches were characterized for morphology (scanning electron microscope), crystallinity (Fourier transform intra-red spectroscopy, FTIR and X-ray diffractometer, XRD), thermal flow (differential scanning colorimeter), density and flow properties. Theophylline microbeads were prepared by ionic gelation and characterized using size, swelling index, entrapment efficiency and time required for 15% and 50% drug release (t15 and t50 respectively). Results: FTIR and XRD spectra revealed the orderly arrangement of granules of the semi-crystalline breadfruit starch was disrupted on gelatinization. The viscosity and flow of pregelatinized starch were enhanced. Theophylline microbeads were near spherical in shape with size range 1.09 ± 0.672 to 1.58 ± 0.54 mm. FTIR and XRD spectra confirmed there was no drug-polymer interaction. Microsphere size, swelling increased while entrapment and dissolution time (t50) reduced with polymer: drug ratio. The entrapment efficiency ranged from 30.99 ± 1.32 to 78.50 ± 2.37%. Optimized formulation, starch: alginate ratio 3:1 at polymer: drug ratio of 2:1, gave a prolonged dissolution time (t50 = 8.40 ± 1.20 h). Conclusion: Breadfruit starch was suitable as a copolymer for the controlled delivery of theophylline in microbeads which could serve as a substitute to synthetic polymers in drug delivery.

Development of repaglinide microspheres using novel acetylated starches of bitter and Chinese yams as polymers.

Tropical starches from Dioscorea dumetorum (bitter) and Dioscorea oppositifolia (Chinese) yams were acetylated with acetic anhydride in pyridine medium and utilized as polymers for the delivery of repaglinide in microsphere formulations in comparison to ethyl cellulose. Acetylated starches of bitter and Chinese yams with degrees of substitution of 2.56 and 2.70 respectively were obtained. Acetylation was confirmed by FTIR, 1H NMR spectroscopy. A 32 factorial experimental design was performed using polymer type and drug-polymer ratio as independent variables. Particle size, swelling, entrapment and time for 50% drug release (t50) were dependent variables. Contour plots showed the relationship between the independent factors and the response variables. All variables except swelling increased with drug: polymer ratio. Entrapment efficiency was generally in the rank of Bitter yam>Ethyl cellulose>Chinese yam. Repaglinide microspheres had size 50±4.00 to 350±18.10µm, entrapment efficiency 75.30±3.03 to 93.10±2.75% and t50 3.20±0.42 to 7.20±0.55h. Bitter yam starch gave longer dissolution times than Chinese yam starch at all drug-polymer ratios. Drug release fitted Korsmeyer-Peppas and Hopfenberg models. Acetylated bitter and Chinese yam starches were found suitable as polymers to prolong release of repaglinide in microsphere formulations.

Design of cissus-alginate microbeads revealing mucoprotection properties in anti-inflammatory therapy.

Cissus gum has been employed as polymer with sodium alginate in the formulation of diclofenac microbeads and the in vivo mucoprotective properties of the polymer in anti-inflammatory therapy assessed in rats with carrageenan-induced paw edema in comparison to diclofenac powder and commercial diclofenac tablet. A full 2(3) factorial experimental design has been used to investigate the influence of concentration of cissus gum (X1); concentration of calcium acetate (X2) and stirring speed (X3) on properties of the microbeads. Optimized small discrete microbeads with size of 1.22±0.10 mm, entrapment efficiency of 84.6% and t80 of 15.2±3.5 h were obtained at ratio of cissus gum:alginate (1:1), low concentration of calcium acetate (5% w/v) and high stirring speed (400 rpm). In vivo studies showed that the ranking of percent inhibition of inflammation after 3h was diclofenac powder>commercial tablet=cissus>alginate. Histological damage score and parietal cell density were lower while crypt depth and mucosal width were significantly higher (p<0.05) in the groups administered with the diclofenac microbeads than those administered with diclofenac powder and commercial tablet, suggesting the mucoprotective property of the gum. Thus, cissus gum could be suitable as polymer in the formulation of non-steroidal anti-inflammatory drugs ensuring sustained release while reducing gastric side effects.

Design of bilayer tablets using modified Dioscorea starches as novel excipients for immediate and sustained release of aceclofenac sodium.

Bilayer tablets of aceclofenac sodium were developed using carboxymethylated white yam (Dioscorea rotundata) starch (CWY) for a fast release layer (2.5, 5.0, and 7.5% w/w), and acid-hydrolyzed bitter yam (Dioscorea dumetorum) starch (ABY) for a sustaining layer (27% w/w). Sodium starch glycolate (SSG) and hydroxypropyl methyl cellulose (HPMC) were used as standards. The starches were characterized using Fourier Transform Infrared spectroscopy (FT-IR), particle size, swelling power, densities and flow analyses. Mechanical properties of the tablets were evaluated using crushing strength and friability while release properties were evaluated using disintegration and dissolution times. Distinctive fingerprint differences between the native and modified starches were revealed by FT-IR. Carboxymethylation produced starches of significantly (p < 0.05) higher swelling and flow properties while acid-modification produced starches of higher compressibility. Bilayer tablets containing ABY had significantly higher crushing strength and lower friability values (p < 0.05) than those containing HPMC. Crushing strength increased while friability values decreased with increase in CWY. Generally tablets containing the modified Dioscorea starches gave faster (p < 0.05) disintegration times and produced an initial burst release to provide the loading dose of the drug from the immediate-release layer followed by sustained release (300 ± 7.56-450 ± 11.55 min). The correlation coefficient (R (2)) and chi-square (χ(2)) test were employed as error analysis methods to determine the best-fitting drug release kinetic equations. In vitro dissolution kinetics generally followed the Higuchi and Hixson-Crowell models via a non-Fickian diffusion-controlled release. Carboxymethylated white yam starch and acid-modified bitter yam starch could serve as cheaper alternative excipients in bilayer tablet formulations for immediate and sustained release of drugs respectively, particularly where high mechanical strength is required.

Microbead design for sustained drug release using four natural gums.

Four natural gums, namely albizia, cissus, irvingia and khaya gums have been characterized and evaluated as polymers for the formulation of microbeads for controlled delivery of diclofenac sodium. The natural gums were characterized for their material properties using standard methods. Diclofenac microbeads were prepared by ionotropic gelation using gel blends of the natural gums and sodium alginate at different ratios and zinc chloride solution (10%w/v) as the crosslinking agent. The microbeads were assessed using SEM, swelling characteristics, drug entrapment efficiencies and release properties. Data obtained from in vitro dissolution studies were fitted to various kinetic equations to determine the kinetics and mechanisms of drug release, and the similarity factor, f2, was used to compare the different formulations. The results showed that the natural gum polymers varied considerably in their material properties. Spherical and discrete microbeads with particle size of 1.48-2.41 µm were obtained with entrapment efficiencies of 44.0-71.3%w/w. Drug release was found to depend on the type and concentration of polymer gum used with formulations containing gum:alginate ratio of 3:1 showing the highest dissolution times. Controlled release of diclofenac was obtained over for 5h. Drug release from the beads containing the polymer blends of the four gums and sodium alginate fitted the Korsmeyer-Peppas model which appeared to be dependent on the nature of natural gum in the polymer blend while the beads containing alginate alone fitted the Hopfenberg model. Beads containing albizia and cissus had comparable release profiles to those containing khaya (f2>50). The results suggest that the natural gums could be potentially useful for the formulation controlled release microbeads.

Characterization and evaluation of acid-modified starch of Dioscorea oppositifolia (Chinese yam) as a binder in chloroquine phosphate tablets

Chinese yam (Dioscorea oppositifolia) starch modified by acid hydrolysis was characterized and compared with native starch as a binder in chloroquine phosphate tablet formulations. The physicochemical and compressional properties (using density measurements and the Heckel and Kawakita equations) of modified Chinese yam starch were determined, and its quantitative effects as a binder on the mechanical and release properties of chloroquine phosphate were analyzed using a 2³ full factorial design. The nature (X1), concentration of starch (X2) and packing fraction (X3) were taken as independent variables and the crushing strength-friability ratio (CSFR), disintegration time (DT) and dissolution time (t80) as dependent variables. Acid-modified Chinese yam starch showed a marked reduction (p<0.05) in amylose content and viscosity but increased swelling and water-binding properties. The modified starch had a faster onset and greater amount of plastic flow. Changing the binder from native to acid-modified form led to significant increases (p<0.05) in CSFR and DT but a decrease in t80. An increase in binder concentration and packing fraction gave similar results for CSFR and DT only. These results suggest that acid-modified Chinese yam starches may be useful as tablet binders when high bond strength and fast dissolution are required.

Amido de inhame chinês (Dioscorea oppositifolia), modificado por meio de hidrólise ácida, foi caracterizado e avaliado como aglutinante em formulações de comprimidos de fosfato de cloroquina, em comparação com o amido nativo. Determinaram-se as propriedades físico-químicas e de compressão (utilizando medidas de densidade e as equações de Heckel e Kawakita). Os efeitos quantitativos do amido modificado como ligante sobre as propriedades mecânicas e de liberação de fosfato de cloroquina foram analisados por meio de um planejamento fatorial completo 2³. Tomaram-se a natureza (X1), a concentração de amido (X2) e a fração de empacotamento (X3) como variáveis independentes e relação força de compressão-friabilidade (RFCE), tempo de desintegração (DT) e tempo de dissolução (t80), como variáveis dependentes. O amido de inhame chinês modificado mostrou redução marcante (p<0,05) no teor de amilose e da viscosidade, mas aumento no inchamento e nas propriedades de ligação de água. O amido modificado teve início rápido e maior quantidade de fluxo plástico. A alteração do aglomerante da forma nativa para a modificada com ácido conduziu a aumento significativo (p <0,05) em CSFR e DT, mas diminuição da t80. O aumento da concentração do aglutinante e da fração de empacotamento deu origem a resultados semelhantes apenas para RFCE e DT. Os resultados sugerem que os amidos modificados com ácido do inhame chinês podem ser mais úteis como aglutinantes de comprimidos, quando se necessitam de força de ligação alta e de dissolução rápida..

Evaluation of starches obtained from four Dioscorea species as binding agent in chloroquine phosphate tablet formulations.

Starches obtained from four Dioscorea species namely Dioscorea dumetorum (Bitter), Dioscorea oppositifolia (Chinese), Dioscorea alata (Water), and Dioscorea rotundata (White) have been evaluated as binding agents in chloroquine phosphate tablet formulations in comparison with official corn starch. The compressional properties of the formulations were analyzed using density measurements and the Heckel and Kawakita equations. The mechanical properties of the tablets were assessed using tensile strength, brittle fracture index (BFI), and friability tests while the drug release properties of the tablets were assessed using disintegration and dissolution times. The results indicate that the four starches vary considerably in their physicochemical properties. The ranking for the tensile strength and the disintegration and dissolution times for the formulations was Chinese > Bitter > Corn > White > Water while the ranking was reversed for BFI and friability. The results suggest that Water, White, and Corn could be useful when faster disintegration time of tablets is desired while Chinese and Bitter could be more useful when bond strength is of concern and in minimizing the problems of lamination and capping in tablet formulation.