The effect of geometric shape on the release properties of metronidazole from lipid matrix tablets

PubMed ID: 20055089In this study, the lipophilic matrix tablets of metronidazole were prepared with Cutina HR (hydrogenated castor oil), stearic acid, Compritol ATO 888 (glyceryl behenate) and Precirol ATO 5 (glycerol palmitostearate) in two different shapes; cylinder and hexagonal. Our first aim was to investigate the influence of the lipid excipients and geometric shape on the release behavior of metronidazole, and the second aim was to investigate the influence of tablet surface area/volume (SA/V) ratio on drug release from controlled release matrix tablets. In vitro release test was performed using a standard USP dissolution apparatus I. Hardness, surface/volume ratio and friability were determined. The hexagonal tablets were harder than the cylinder tablets. Stearic acid showed the highest release rates for both geometric shapes reflecting the highest surface area and the lowest SA/V ratio. According to power law analysis, the diffusion mechanism was expressed as a Fickian diffusion for all lipid matrix tablets. The square root of time relationship was operative for all tablets. Higuchi kinetic constants obtained with hexagonal tablets were higher than the cylinder tablets. As the type of lipid matrix, the geometric shape of the tablets was also effective on the diffusion and release kinetics. From the present study, it was shown that surface area and volume ratio may be used as parameters for the evaluation of the drug release profile. Copyright © 2009 American Scientific Publishers All rights reserved

Micromeritic studies on nicardipine hydrchloride microcapsules

In this study, nicardipine hydrochloride (N.HCl) microcapsules were prepared by means of coacervation phase separation technique using ethylcellulse (EC) as a coating material. Micromeritic investigations were carried out on nicardipine hydrochloride, ethylellulose and nicardipine hydrochloride microcapsules in order to standardize the microcapsule product and to optimize the pilot production of dosage forms prepared with these microcapsules. Microcapsules we prepared had the ratio of 2:1 core:wall and then by sieving, were divided into two groups according to their particle sizes which were > 840 µm and 476-840 µm. The bulk volume and weight, tapping volume and weight, fluidity, angle of repose, weight deviation, particle size distribution, density and porosity of nicardipine hydrochloride, ethylcellulose and nicardipine hydrochloride microcapsules were studied. To determine flowability, Hausner ratio and Consolidation index were also calculated from the results obtained. The findings of the study suggested that the micromeritic properties of the crude materials were significantly changed by the microencapsulation process. In addition, it was shown by scanning electron microscopy, that the changes were due to changes in the physicochemical properties of drug particles.The authors wish to thank the ResearchF oun-dation of Ege University for financial support given to this study. They also wish to thank Sandoz PharmaceuticaClo mpanyfor their gift of nicardipineh ydrochloride. -

Sustained-release dosage form of phenylpropanolamine hydrochloride. Part II: Formulation and in vitro release kinetics from tableted microcapsules

PubMed ID: 8064557This work was planned to prepare sustained-action preparations of phenylpropanolamine hydrochloride by microencapsulation and by tableted microcapsules. Dissolution from both suspended microcapsules and the tablets was studied using the USP XXII basket method in simulated gastric and intestinal fluid without enzyme. The results were applied to zero-order, first-order, Hixson Crowell, RRSBW, Q/{check mark}t, (Bt)a and Higuchi kinetic models. Dissolution of PPA.HC1 was found to be governed by the core: wall ratio, drug particle size, media pH and type of disintegrating agent. Dissolution kinetics were studied and evaluated. © 1994 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted

Release and diffusional modeling of metronidazole lipid matrices

PubMed ID: 16621486In this study, the first aim was to investigate the swelling and relaxation properties of lipid matrix on diffusional exponent (n). The second aim was to determine the desired release profile of metronidazole lipid matrix tablets. We prepared metronidazole lipid matrix granules using Carnauba wax, Beeswax, Stearic acid, Cutina HR, Precirol® ATO 5, and Compritol® ATO 888 by hot fusion method and pressed the tablets of these granules. In vitro release test was performed using a standard USP dissolution apparatus I (basket method) with a stirring rate of 100 rpm at 37 °C in 900 ml of 0.1 N hydrochloric acid, adjusted to pH 1.2, as medium for the formulations' screening. Hardness, diameter-height ratio, friability, and swelling ratio were determined. Target release profile of metronidazole was also drawn. Stearic acid showed the highest and Carnauba wax showed the lowest release rates in all formulations used. Swelling ratios were calculated after the dissolution of tablets as 9.24%, 6.03%, 1.74%, and 1.07% for Cutina HR, Beeswax, Precirol® ATO 5, and Compritol® ATO 888, respectively. There was erosion in Stearic acid, but neither erosion nor swelling in Carnauba wax, was detected. According to the power law analysis, the diffusion mechanism was expressed as pure Fickian for Stearic acid and Carnauba wax and the coupling of Fickian and relaxation contributions for other Cutina HR, Beeswax, Compritol® ATO 888, and Precirol® ATO 5 tablets. It was found that Beeswax (kd = 2.13) has a very close drug release rate with the target profile (kt = 1.95). Our results suggested that swelling and relaxation properties of lipid matrices should be examined together for a correct evaluation on drug diffusion mechanism of insoluble matrices. © 2006 Elsevier B.V. All rights reserved