In vitro study of allantoin release from various ointment formulations.
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Biomedical subjects
Publications and source records attributed to M Sznitowska.
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Submicron emulsions containing 2.0% w/v pilocarpine as pilocarpine HCl, soybean oil (10% w/v) and egg lecithin (1.2% w/v) were formulated. Emulsions at pH 5.0, 6.5 and 8.5 were applied to the rabbit's eye, and the reduction in pupil diameter was measured for 6 h. The miotic effect was compared with that obtained with aqueous solutions at the same pH. A prolonged miotic effect was observed when the submicron emulsion was used as a vehicle. After application of emulsions at pH 5.0, 6.5 or 8.5, the time when 20% reduction of pupil diameter was still observed was 3.9 +/- 1.1 h, 4.3 +/- 1.3 h and 5.3 +/- 0.8 h, respectively, while, after application of a solution, this parameter was shorter by 30-40%. AUC(0-6h) values were larger after application of the submicron emulsions in comparison to aqueous solutions; however, statistically significant differences were only observed for emulsions at pH 6.5. Although the bioavailability of the drug is pH dependent, emulsions at higher pH cannot be considered for clinical use because of pilocarpine degradation which occurs with a similar rate as in aqueous solutions. Introduction of pilocarpine into the oily phase in the form of pilocarpine base or its oleate did not improve either the physicochemical or the pharmacological properties of the formulations. Irrespective of the pH and chemical form of pilocarpine used for emulsion preparation, practically all drug was found in the aqueous phase of the emulsion; thus, partitioning to the oily phase was negligible.
Diazepam was incorporated in lipospheres prepared by high pressure homogenization of melted Witepsol (10%) dispersed in aqueous lecithin (2.4%). Diazepam content was 0.4% and more than 98% of the dose was found to be encapsulated in the lipospheres. Although the initial mean particle size was 0.3 micron, the liposhperes agglomerated during storage and this phenomenon was not eliminated by increasing lecithin concentration to 4% or incorporation of oleic acid (0.1%) and co-surfactants, polysorbate 80 (0.5%) or poloxamer (up to 6%). The formulation was not able to mask effectively bitter taste of diazepam, even when lipids of higher melting temperature, namely glyceryl tripalmitate or stearic acid, were introduced.
A 24-h extended-release multiparticulate capsule containing a dose of 500 mg of lithium carbonate divided into 6 tablets 6 mm in size was produced. In order to achieve an immediate and prolonged drug release profile one uncoated tablet and 5 tablets coated with methacrylic acid/ethyl acrylate copolymer Kollicoat MAE30DP were filled into a capsule. The core of tablets consisted of microcrystalline cellulose, lactose, povidone, macrogol and magnesium stearate.
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