Incorporation of alphaxalone into different types of liposomes

The characterization and biodistribution of cefoxitin-loaded liposomes

To conquer the clinical restriction of relative short half-life and poor tissue retaining activities, liposomes containing cefoxitin were prepared using three methods in this study. The physicochemical properties including cefoxitin encapsulation percentage, vesicle size, stability, as well as the in vivo biodistribution were studied. The highest entrapment percentage was observed by using reverse phase evaporation method, and the molar ratio of cefoxitin to phospholipids was 1:3, DMPC to cholesterol was 2:1, respectively. From the result of stability, the freeze-drying powder and then stored in the frozen condition of cefoxitin-loaded liposome was an ideal storage state. Accordingly, the formulation by reverse-phase evaporation method was selected to investigate the biodistribution of cefoxitin-loaded liposome and compared to free cefoxitin in rats. It was observed that the cefoxitin levels and the duration retained in the liver, spleen, and pancreas of liposome-injected animals were higher and longer than that of free cefoxitin-injected animals. The drug concentrations of bile after post-injection of liposomal cefoxitin at 0.5, 1 and 2 h were all approximately 2.7 times higher than that of free cefoxitin injection group.

The anaesthetic action and modulation of GABAA receptor activity by the novel water-soluble aminosteroid Org 20599

The anaesthetic profile of a novel water-soluble aminosteroid, Org 20599 [(2 beta, 3 alpha, 5 alpha)-21-chloro-3-hydroxy-2-(4-morpholinyl)pregnan-20-one methanesulphonate], and the ability of the compound to allosterically regulate the activity of the GABAA receptor, have been studied in comparison to the properties of established intravenous general-anaesthetic agents. Intravenously administered Org 20599 produced a rapid onset, short duration loss of the righting reflex in mice. The anaesthetic potency of Org 20599 was comparable to that of the steroids 5 alpha-pregnan-3 alpha-ol-20-one or alphaxalone, and exceeded that of propofol, thiopentone or pentobarbitone. Org 20599 and the reference anaesthetic agents allosterically displaced the binding of [35S]-t-butylbicyclophosphorothionate (TBPS) from GABAA receptors of rat-brain membranes with the order of potency: 5 alpha-pregnan-3 alpha-ol-20-one > Org 20599 > alphaxalone > propofol > thiopentone > pentobarbitone. At human recombinant alpha 1, beta 2, gamma 2L subunit-containing GABAA receptors expressed in Xenopus laevis oocytes, the anaesthetic agents produced a concentration-dependent and reversible potentiation of the peak amplitude of GABA-evoked currents. A similar positive allosteric action of Org 20599 was observed for the GABAA receptors expressed by bovine adrenal chromaffin cells maintained in culture. The rank order of potency in the aforementioned assays was identical to that determined from the displacement of TBPS binding. At concentrations greater than those required for potentiation of GABA, the anaesthetics exhibited GABA-mimetic effects with a rank order of potency that paralleled their modulatory activity. Such direct agonism varied greatly in maximal effect between compounds. The modulatory and direct agonist actions of Org 20599 were additionally confirmed utilizing rat hippocampal neurones in culture. The results indicate Org 20599 to be a potent and short-acting intravenous anaesthetic agent in mice and suggest positive allosteric regulation of GABAA receptor function to be a plausible molecular mechanism of action for the drug.