Leuprorelin (leuprolide, D-Leu6-(des-Gly10-NH2)-LH-RH ethylamide) acetate is a superactive agonist of luteinizing hormone-releasing hormone (LH-RH). We developed once-a-month injectable microcapsules of this agonist by our novel in-water drying method. This depot formulation can release the drug at an apparent zero-order rate over one month with bioerosion of copoly (lactic/glycolic acid) utilized as a wall material of the polycore microcapsules. A dramatic prolonged depression of pituitary-gonadal axis, chemical castration, was achieved by the once-a-month injection in experimental animals ; it expects a reliable effcacy for treating hormone-dependent prostatic, breast cancers and endometriosis. Studies on the dosage design of this new delivery system of leuprorelin are summarized.
Various lipid molecular assemblies, monolayer, bilayer, emulsion particle, hexagonal II phase and micellar particle, are in dynamic equilibrium in an animal body. Monolayer-bilayer equilibrium of a mixture of phospholipid and neutral lipid is influenced by the phase state of bilayer and molecular interaction of lipids. Neutral lipids, such as triglyceride, cholesterylester, ubiqinone-10 and α-tocopherol acetate form an emulsion structure with phosphatidylcholine (PC). Stable emulsion particles (neutral lipid core covered with PC monolayer) are in equilibrium with liposome particles (PC bilayers). This kind of equilibrium is important in catabolism of triglyceride-rich lipoprotein particles and artificial emulsion particles, Intralipid, in the plasma. Some other neutral lipids, such as diglyceride, menaquinone-4 and α-tocopherol induce a formation of intra-and inter-bilayer particles in PC bilayer, and finally transform it to hexagonal II phase. This type of neutral lipids has been implicated in several cellular processes : vesiculation, fusion, endocytosis and exocytosis etc. More hydrophilic lipid, such as cholate, or protein with amphiphatic helix, such as apoA-1, strongly interact with PC bilayer and transform it to micellar particles ; mixed disk micellar or high density lipoprotein particles. Phospholipid bilayer, therefore, converts into various nonbilayer structures by interaction with neutral lipid and protein in an animal body.
To reduce the vascular contracting effect of the cardiac glycoside, proscillaridin (1), all kinds of its nitrates were prepared by utilizing effectively an isopropylidene function as a protective group. The pharmacological activities of proscillaridin nitrates were evaluated by the use of isolated guinea-pig papillary muscle preparations and Na+, K+-adenosine triphosphatase preparations from the dog kidney. Furthermore, the effect for smooth muscle using the helical strips isolated from 13-week old spontaneously hypertensive rat was examined. The positive inotropic effects and Na+, K+-adenosine triphosphatase inhibition activities of mononitrates (6, 9, 15) and dinitrates (3, 4, 5) were a little less potent than 1, but those of trinitrate (2) were much reduced. Every nitrate did not exhibited a vascular contracting effect but a relaxing effect. Among them, the vascular relaxing effects of 2', 3'-dinitrate (3) and 2', 4'-dinitrate (4) were more potent than those of the other nitrates.
The effects of triglycerides on the gastrointestinal absorption of 2-[3-(3, 5-di-tert-butyl-4-hydroxyphenyl)-1H-pyrazolo [3, 4-b] pyridin-1-yl] ethyl acetate (1) were investigated in dogs. The enhancing abilities of the triglycerides on the absorption of 1 were demonstrated as in the order of trilinolein>triolein>tristearin>tripalmitin. Among the series of fatty acids and monoglycerides, namely, digestive products of triglycerides by pancreatic lipase, linoleic acid and monolinolein showed the most potent solubilizing activities of 1 in a solution of bile salt. The incorporation of 1 into mixed micelle formed by lipids and bile salts was presumed to play an important role in the accelerated absorption of 1 after ingestion of triglycerides. On the basis of these findings, an emulsion containing 1 was prepared with soybean oil. The emulsion exhibited a remarkable improvement of the absorption of 1 compared to a suspension of the drug in methylcellulose solution.
Agglomeration mechanism of the spherical crystallization of a water soluble drug by the emulsion solvent diffusion method was investigated with a mixed system of two or three partially miscible solvents, i. e., bridging liquid-poor solvent system or good solventbridging liquid-poor solvent system. When bridging liquid (or plus good solvent) solution of the drug was poured into poor solvent (=dispersing medium) under agitation, quasi emulsion droplets of bridging liquid or good solvent were produced. The diffusion of bridging liquid or good solvent from the emulsion droplet into the dispersing medium induced the crystallization of drug, which was clearly monitored by an X-ray diffraction analysis. Seeding the drug crystals to the system enhanced the solidification of emulsion droplets, resulting improved agglomeration. The agglomerated crystals had the most thermodynamically stable crystalline form. Both hydrophilic and hydrophobic polymers could be coprecipitated into the agglomerated crystals to modify the physicochemical properties of raw crystals of the drug. A closed circuit batch operation system was proposed to use repeatedly the dispersing medium recovered after each operation for industrialization.
Pyrene-1-carbonyl fluoride (PCF) was synthesized as a precolumn fluorescent labeling reagent for alcohols and amines for use in high performance liquid chromatography (HPLC). PCF reacted with primary and phenolic hydroxyl groups in dichloromethane at 100°C for 30 min in the presence of 4-dimethylaminopyridine (DMAP) to give the corresponding fluorescent pyrene esters and also reacted with primary amines in acetonitrile at room temperature for 2 min in the presence of DMAP to give the amides. The PCF esters of corticosteroids were separated by normal-phase chromatography on a Cosmosil 5 SL column with hexane-ethyl acetate (6 : 5, v/v) and the PCF amides of primary amines were separated by reversed-phase chromatography on a TSK gel ODS-80 TM column with methanol-water (10 : 3, v/v). The detection limits (S/N=3) of cortisone and 2-phenyl-ethylamine were 600 fmol and 800 fmol for an injection volume of 10μl, respectively.