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Cumulative Release (cumulative + release)
Selected AbstractsNovel colon-specific microspheres with highly dispersed hydroxycamptothecin cores: Their preparation, release behavior, and therapeutic efficiency against colonic cancerJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2006Bin Lu Abstract To increase therapeutic efficiency of hydroxycamptothecin (HCPT) against colonic cancer and decrease its side-effects, highly dispersed HCPT was first incorporated in fast release microspheres. HCPT in the microspheres showed a solubility two times larger, and its cumulative release rate for 24 h in simulated colonic juice 140 times higher than that of free HCPT. The microspheres were then coated with a layer of Eudragit S100 by air suspension spray-drying method with a selfdesigned device to obtain colon-specific microspheres (HCPT,CSMS). The mean particle size of the microspheres was 200 µm before coating and 230 µm after coating. The in vitro cumulative release results for HCPT,CSMS in simulated gastric juice for 2 h, in simulated enteric juice for 4 h, and in simulated colonic juice for 18 h showed that over 60% of total HCPT released in simulated colonic juice in the initial 5 h. Animal tests with per os (po) administration showed that free HCPT was mainly absorbed in stomach and small intestine, while the HCPT in HCPT,CSMS was mainly delivered and absorbed in colon. po administration of HCPT,CSMS to nude mice with colonic cancer showed a cancer inhibition rate of 61.4% compared to 39.8% for free HCPT. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:2619,2630, 2006 [source] Synthesis and evaluation of ampicillin-conjugated gum arabic microspheres for sustained releaseJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 4 2007K. K. Nishi Ampicillin was conjugated to periodate-oxidized gum arabic (GA), a branched polysaccharide, to form the imino conjugate of the drug and the polysaccharide. The water-soluble conjugate was dispersed by sonication in a mixture of toluene and liquid paraffin in the presence of a non-ionic surfactant as droplet stabilizer and fabricated into microspheres by heat denaturation at 80°C to obtain spheres less than 2 ,m in diameter. These microspheres did not undergo dissolution in water on prolonged incubation. In-vitro release of ampicillin into phosphate buffer from the microspheres was slow and sustained with a cumulative release between 10 and 25% of the drug content in 10 days depending on the degree of oxidation of GA and the drug payload. Release into simulated gastric fluid was faster due to faster hydrolysis of the drug-GA bond in the acid medium, but when the medium was changed to intestinal fluid, the release was slowed down. Ampicillin released was functionally active and inhibited the growth of S. aureus and E. coli in cultures, although not as actively as free ampicillin. The microspheres underwent slow biodegradation on prolonged incubation in aqueous media. These studies show that ampicillin conjugated with oxidized GA and fabricated into microspheres possesses sustained-release characteristics for prolonged periods. [source] Gelatin Microspheres as a Pulmonary Delivery System: Evaluation of Salmon Calcitonin AbsorptionJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 6 2000KAZUHIRO MORIMOTO The use of negatively and positively charged gelatin microspheres for pulmonary delivery of salmon calcitonin was examined in rats. The microspheres were prepared using acidic gelatin (isoelectric point (IEP):, 5.0) and basic gelatin (IEP, 9.0) for the negatively and positively charged microspheres, respectively. The average diameters of positively charged gelatin microspheres in the dry state were 3.4, 11.2, 22.5 and 71.5 ,m, and that of negatively charged gelatin microspheres was 10.9 ,m. Neither positively nor negatively charged gelatin microspheres underwent any degradation in pH 7.0 PBS and there was less than 8% degradation in bronchoalveolar lavage fluid (BALF) after 8 h. In in-vitro release studies in pH 7.0 PBS, salmon calcitonin was rapidly released from positively charged gelatin microspheres within 2 h, and its cumulative release was approximately 85%. In addition, the release profiles were not influenced by particle sizes. The release rates of salmon calcitonin from negatively charged gelatin microspheres were lower than that from positively charged gelatin microspheres. The cumulative release was approximately 40% after 2 h, but there was no evidence of any sustained release. The pulmonary absorption of salmon calcitonin from gelatin microspheres was estimated by measuring its hypocalcaemic effect in rats. The pharmacological availability after administration of salmon calcitonin in positively and negatively charged gelatin microspheres was significantly higher than that in pH 7.0 PBS. The pharmacological availability after administration of salmon calcitonin in positively charged gelatin microspheres was significantly higher than that in negatively charged gelatin microspheres. Administration of salmon calcitonin in positively charged gelatin microspheres with smaller particle sizes led to a higher pharmacological availability. The pharmacological availability after pulmonary administration of salmon calcitonin in positively charged gelatin microspheres with particle sizes of 3.4 and 11.2 ,m was approximately 50%. In conclusion, the gelatin microspheres have been shown to be a useful vehicle for pulmonary delivery of salmon calcitonin. [source] Sodium hyaluronate gels as a drug-release system for corticosteroids: release kinetics and antiproliferative potential for glaucoma surgeryACTA OPHTHALMOLOGICA, Issue 8 2008Martin S. Spitzer Abstract. Purpose:, To evaluate the release kinetics, biocompatibility and antiproliferative potential of a concentrated hydrophilic steroid formulation from commercially available sodium hyaluronate gels as a potential adjunct in glaucoma surgery. Methods:, Dexamethasone and sodium hyaluronate 1% (Healon) and sodium hyaluronate 2.3% (Healon 5) were mixed to yield sodium hyaluronate formulations containing dexamethasone in concentrations of 4,20 mg/ml (7.7,38 mm). Non-cumulative and cumulative release into balanced salt solution (BSS) or phosphate buffered saline (PBS) was measured spectrophotometrically over 2,6 days. For cytotoxicity assays, human tenon fibroblasts (HTFB) and human retinal pigment epithelium cells (ARPE19) were cultured in a serum-deficient medium to ensure a static milieu; 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazoliumbromide (MTT) assay and Live/DeadÔ cell-mediated cytotoxicity assay were used to exclude cytotoxicity. Cellular proliferative activity was monitored by 5,-bromo-2,-deoxyuridine (BrdU)-incorporation into cellular DNA. Results:, The release kinetics from sodium hyaluronate 1% and 2.3% were almost identical. Steady state was achieved after approximately 44 hrs in non-cumulative measurements. The release plotted as a function of the square root of time was consistent with a largely diffusion-controlled release system. No cytotoxicity could be observed. Dexamethasone-loaded sodium hyaluronate showed a significant antiproliferative effect on HTFB and ARPE19 cells. Conclusion:, Dexamethasone-loaded sodium hyaluronate shows extended release of steroid over almost 2 days in concentrations high enough to inhibit the proliferation of HTFB and RPE cells without evoking cytotoxic effects. Thus, this formulation may be an easy-to-prepare adjunct in glaucoma surgery or other procedures in which cellular growth inhibition is desired. [source] | ||||||||||