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Biomedical subjects

H Kokubo

Publications and source records attributed to H Kokubo.

23 records · Page 2Linked to original sources
PubMed1992

Studies on single-dose toxicity of hydrophobically modified hydroxypropyl methylcellulose in rats.

Single-dose toxicological studies of hydrophobically modified hydroxypropyl methylcellulose (HM-HPMC, hydroxypropyl methylcellulose modified with stearylglycidylether) were conducted. A dispersion of HM-HPMC was administered to rats orally or by dermal application at doses up to 900 mg/kg. After the oral administration, the mean body weight of the 900 mg/kg group on the first day after administration was slightly but significantly lower (P less than 0.05) than that of the control group, and one rat had loose stools at 30 min. after the administration. No other abnormalities were noted. In the case of dermal application, no abnormalities were observed. No rats died, and no abnormalities in their organs were found by either route. In conclusion, there was no observed toxicity of HM-HMPC after oral or dermal administration at single dose up to 900 mg/kg under the conditions of these studies.

Administration, Cutaneous↗
PubMed1992

Primary dermal and eye irritability tests of hydrophobically modified hydroxypropyl methylcellulose in rabbits.

Primary dermal and eye irritation tests of hydrophobically modified hydroxypropyl methylcellulose (HM-HPMC, hydroxypropyl methylcellulose modified with stearylglycidylether), a new cellulose derivative used as a thickener for topical pharmaceuticals and cosmetics, were conducted in rabbits. A dispersion of HM-HPMC (3%) was applied to intact and abraded skins and reactions were observed. A very slight erythema was observed in both skins and this polymer was categorized as a "mild irritant". In the eye irritation test, with a dispersion of the same concentration, it was categorized as "marginal" in unrinsed eyes and "negative" in rinsed eyes.

Administration, Cutaneous↗
PubMed1983

X-ray structural studies and physicochemical properties of cimetidine polymorphism.

Four crystalline forms of cimetidine, three anhydrous (forms A, B, and D) and a monohydrate (form C), obtained by slow evaporation of aqueous solutions of varying concentrations were characterized by IR spectroscopy, X-ray powder patterns, dissolution rates in deionized water, and thermal analyses. Among the three anhydrous forms of cimetidine, form A was thermodynamically more stable than the others. The structural conversion of form C into form A on dehydration was confirmed by IR spectroscopy and X-ray powder patterns. The structures of forms C and D were determined using X-ray diffraction. Form D was of spirally curled conformation; it was linked in a head-to-tail arrangement with the neighboring molecules via intermolecular hydrogen bonds between the imidazole nitrogen and guanidine nitrogen atoms. Form C was characterized by its folded conformation due to the weak stacking interaction between the imidazole and guanidine moieties; there was stabilization by double hydrogen bond formation with neighboring molecules and via water molecules of crystallization. The dissolution rate constant in deionized water for form C was approximately 1.29, 1.70, and 1.90 times greater than those measured for forms A, D, and B, respectively. There was a similar relationship among the four forms with respect to the rates of inhibition of stress ulceration. Regarding the molecular conformations of the crystalline forms and the rates of inhibition of stress ulceration, the gauche orientation of the guanidine group relative to the imidazole ring would be the conformation necessary for effective binding to the histamine H2-receptor. The compactly folded conformation of form C appears to be optimal for binding to the active site of the receptor and for clinical efficacy.

Animals↗