title: Preparation and evaluation of suppositories for RK-28 (a new radiosensitizer) using rabbits.
abstract: The pharmacokinetics of RK-28 [1-(4-hydroxy-2-butenoxy)methyl-2-nitroimidazole], a new hypoxic cell radiosensitizer, was studied following intravenous, oral, and rectal administration to rabbits. After an oral administration of RK-28 solution, the plasma concentration of RK-28 was considerably lower than that after intravenous administration through all time periods, and the absolute bioavailability was a mere 4.2%. It was presumed that a specific acid-catalized decomposition of RK-28 progressed in the stomach, and also, the absorbed RK-28 suffered first-pass effects in the liver. In contrast, the absolute bioavailability following the rectal administration of a solidified RK-28 suppository preparation was significantly increased in comparison with that obtained by other administration routes. Also, RK-28 emulsion suppositories were prepared by emulsifying various amounts of the drug with 1-hexadecanol and hydrogenated castor oil (HCO 60) at 80 degrees C, and these were administered into the rabbit rectum. The resulting absolute bioavailability was 91% for the RK-28 emulsion suppository and 86.9% for an RK-28 emulsion suppository containing small amounts of Eudispert hv. These values were better than those in rats. The rectal administration of the RK-28 emulsion suppository containing small amounts of Eudispert hv showed a preferable plasma concentration-time pattern that reflects on radiation therapy.
authors.affiliation: Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: N S
authors.initials: NS
authors.lastname: Kim
authors.forename: H
authors.initials: H
authors.lastname: Umejima
authors.forename: K
authors.initials: K
authors.lastname: Miyata
authors.forename: M
authors.initials: M
authors.lastname: Okubo
authors.forename: S
authors.initials: S
authors.lastname: Goto
authors.forename: T
authors.initials: T
authors.lastname: Kato
authors.forename: Y
authors.initials: Y
authors.lastname: Mikami
authors.forename: H
authors.initials: H
authors.lastname: Sagitani
authors.forename: H
authors.initials: H
authors.lastname: Inoue
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001682:Biological Availability; D002626:Chemistry, Pharmaceutical; D007275:Injections, Intravenous; D008297:Male; D008920:Misonidazole / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D011817:Rabbits; D011838:Radiation-Sensitizing Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics; D013488:Suppositories
chemical_list: D011838:Radiation-Sensitizing Agents; D013488:Suppositories; C047778:1-(4'-hydroxy-2'-butenoxy)methyl-2-nitroimidazole; D008920:Misonidazole