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Release Medium (release + medium)
Selected AbstractsPreparation and evaluation of poly-butylcyanoacrylate nanoparticles for oral delivery of thymopentinJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2008Weiling He Abstract Thymopentin (Tp5) was loaded in poly-butylcyanoacrylate (PBCA) nanoparticles (NP) in order to enhance the oral bioavailability of Tp5. PBCA-Tp5-NP was prepared by nanoprecipitation methods. Dialyzing membrane method was employed to examine the in vitro release of PBCA-Tp5-NP in PBS, and Tp5 samples in the release medium were detected by HPLC. The cell proliferation test (3H-thymidine) was conducted to verify the PBCA-Tp5-NP bioactivity in vitro. The pharmacodynamical studies were performed on preimmunoinhibited rats and in flow cytometer. The size and the entrapment efficiency of PBCA-Tp5-NP were 178,±,39 nm and 92.21,±,1.08%, respectively. In vitro release data show that less than 60% Tp5 was released from lyophilized PBCA-Tp5-NP while 80% Tp5 was released from the colloidal PBCA-Tp5-NPs in 48 h. The proliferation test showed that PBCA-Tp5-NP had the similar effect as Tp5. The in vivo data showed that oral PBCA-Tp5-NPs had similar function as what intravenous Tp5 did. The oral bioavailability of Tp5 could be enhanced by PBCA nanoparticles. PBCA-Tp5-NP had the property of sustained-release and the efficacy of Tp5 was not changed after formulation. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:2249,2258, 2008 [source] In-vitro release of bupivacaine from injectable lipid formulations investigated by a single drop technique , relation to duration of action in-vivoJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 6 2002Lars Söderberg The aim of this study was to develop an in-vitro release method suitable for injectable slow-release lipid formulations of local anaesthetics (or other drugs). We also aimed that the results of the in-vitro measurements should have a clear relationship to duration of action in-vivo. Six formulations of bupivacaine base in medium-chain triglyceride-glyceryl dilaurate mixtures were developed. A new apparatus was constructed for determination of their in-vitro release profiles. A bulbous glass tube was fixed inside a standard glass bottle, which was then filled with release medium. A stirring magnet was enclosed in the perforated polypropylene cylinder holding the glass tube. The stirring created a continuous, rotating downward flow of medium inside the tube, which kept the lipid phase, introduced by means of a syringe, suspended as a single, free drop. Release profiles were obtained by sampling of the release medium for up to 72 h and analysis by gas-liquid chromatography. The duration of action in-vivo of the respective formulations was tested by the hot-plate method in rats. The release profiles of bupivacaine in-vitro were mono-exponential for four formulations and bi-exponential for the other two. There was a positive correlation between the proportion of glyceryl dilaurate in the formulation and the slow half-life of release of bupivacaine. All formulations showed prolonged duration of action in-vivo, median values within the range 4.5,12 h, as compared with a 2-h effect of bupivacaine hydrochloride solution. A comparison of in-vitro release curves and durations of action in-vivo suggested that to maintain nerve blockade in-vivo the formulations must release bupivacaine at a rate of approximately 350 ,g h,1 under the in-vitro conditions. To conclude, we designed and tested a novel apparatus for measuring release of a local anaesthetic (or other drug) from a fluid or semi-solid formulation in-vitro. Release rates obtained in-vitro by means of this technique may be used to guide the development of formulations with suitable durations of action in-vivo. The apparatus is, however, as yet a prototype. Rigorous evaluation of performance should be carried out on devices built to specific standards according to their intended application. [source] Controlled Delivery Achieved with Bi-Layer Matrix Devices Produced by Co-Injection MouldingMACROMOLECULAR BIOSCIENCE, Issue 8 2004Cláudia M. Vaz Abstract Summary: The aim of this study was to design new soy protein-based bi-layered co-injection moulded matrix systems aimed to achieve controlled drug delivery. The devices consisted of a drug-free outer layer (skin) and a drug-containing core. The systems overcame the inherent disadvantage of non-linear release associated with diffusion-controlled single-layer matrix devices by providing additional releasing area with time to compensate for the decreasing release rate. As expected, the bi-layer devices presented a significant decrease in drug release rate when compared with a correspondent single layer matrix system. The skin thickness and the degree of crosslinking of the core appeared to be very important tools to tailor the release patterns. Furthermore, due to the amphoteric nature of the soy protein, the developed devices evidenced a pH-dependent behaviour. The mechanisms of drug release were also elucidated at two different pH values: i) pH 5.0, near the isoelectric point of soy (low matrix solubility); and ii) pH 7.4, physiological pH (high matrix solubility). Consequently, changing the release medium from pH 5.0 to pH 7.4 after two hours, led to an abrupt increase in drug release and the devices presented a typical controlled drug delivery profile: slow release/fast release. These evidences may provide for the development of individual systems with different release onsets that in combination may exhibit drug releases at predetermined times in a pre-programmed way. Another possibility is the production of three-layer devices presenting bimodal release profiles (fast release/slow release/fast release) by similar technologies. Scanning electron micrograph of a developed bi-layer device. [source] Chitosan-Pectin Composite Gel Spheres: Effect of Some Formulation Variables on Drug ReleaseMACROMOLECULAR SYMPOSIA, Issue 1 2004Pornsak Sriamornsak Abstract Chitosan-pectin composite gel spheres were prepared by ionotropic gelation method. Pectin solution containing indomethacin, a model drug, was extruded into a mixture of chitosan and calcium chloride. The release behavior of indomethacin from composite gel spheres was investigated in-vitro. The influence of factors affecting release behavior, such as type of pectin, molecular weight of chitosan, cross-linking time and release medium, were discussed in this study. Adding chitosan into gelation medium could retard the release of indomethacin from gel spheres. The different type of pectin used demonstrated slightly different drug release profiles. The higher molecular weight of chitosan showed less indomethacin release than the lower one. The increased cross-linking time slowed the drug release from composite gel spheres. The release of indomethacin from composite gel spheres was also dependent on the release medium. The drug release was slower in tris buffer where no phosphate ions which can induce the precipitation of calcium phosphate. The results suggested that the composite gel spheres of pectin and chitosan could be used as a controlled release drug delivery carrier. [source] Preparation and characterization of tetracycline-loaded interpenetrating polymer networks of carboxymethyl cellulose and poly(acrylic acid): water sorption and drug release studyPOLYMER INTERNATIONAL, Issue 10 2005Anil Kumar Bajpai Abstract Tetracycline (TC)-loaded ionic interpenetrating polymer networks (IPNs) of carboxymethyl cellulose (CMC) and crosslinked poly(acrylic acid) (PAA) were prepared and characterized by infrared spectral analysis, differential scanning calorimetry and scanning electron microscopy techniques. The prepared IPNs were evaluated for in vitro blood compatibility by clot formation and hemolysis methods and their water imbibitions capacity was determined. Fractional release dynamics of tetracycline was also investigated from loaded IPNs of CMC and PAA. The entrapped drug was examined for antibacterial activity and structural integrity and effects of various parameters such as percentage loading of the drug, chemical composition of the carrier IPN, pH and temperature of the release medium were investigated on the release profiles of TC. The drug was also released in different simulated biological fluids. Copyright © 2005 Society of Chemical Industry [source] Controlled-release of Avermectin from Organically Modified Hydrotalcite-like Compound NanohybridsCHINESE JOURNAL OF CHEMISTRY, Issue 3 2009Depeng QIU Abstract The intercalation of avermectin (AVM) into sodium dodecyl sulfate (SDS) modified hydrotalcite-like compounds (HTlc) was carried out using an evaporating solvent enhanced intercalation method to obtain AVM-SDS-HTlc nanohybrids. It was found that the nanohybrids could well control the release of avermectin, showing the nanohybrids are a potential pesticide controlled-release formulation. The release of avermectin from AVM-SDS-HTlc nanohybrids is dependent on the pH, temperature and the presence of electrolyte in release medium. Acidic medium and higher temperature and the presence of electrolytes may induce the higher release rate of avermectin. The release process of avermectin from AVM-SDS-HTlc nanohybrids can be described by pseudo-first-order release kinetics, and the activation energy of release is 279 kJ/mol. [source] | |||||||||||||