title: Effect of antacid on absorption of the quinolone lomefloxacin.
abstract: The effect of antacid on the absorption of lomefloxacin (LFLX) in humans was studied. When LFLX was orally administered concomitantly with aluminum- and magnesium-containing antacids under fasting conditions, its level in plasma decreased by one-half and its area under the concentration-time curve was reduced by 40% compared with the levels observed after treatment with LFLX alone. The urinary recovery value also decreased by 40%. No such effects were noted after coadministration of LFLX and a nonmetallic antacid. This study confirmed the existence of chelate complexes of LFLX with Al3+ and Mg2+ and examined the chelating strength. The stability constants of LFLX with Al3+ and Mg2+ were measured and compared with those of ofloxacin and norfloxacin; little difference was observed among them. LFLX was found to bind more strongly with Al3+ than with Mg2+. Further, the existence of chelate formation was proven by 13C-nuclear magnetic resonance spectroscopy. The decrease in the LFLX level in plasma in humans could be explained by a reduced absorption of the Al(3+)- and Mg(2+)-LFLX chelate complexes.
authors.affiliation: St. Marianna University School of Medicine, Institute of Medical Science, Kanagawa, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Shimada
authors.forename: K
authors.initials: K
authors.lastname: Shiba
authors.forename: T
authors.initials: T
authors.lastname: Oguma
authors.forename: H
authors.initials: H
authors.lastname: Miwa
authors.forename: Y
authors.initials: Y
authors.lastname: Yoshimura
authors.forename: T
authors.initials: T
authors.lastname: Nishikawa
authors.forename: Y
authors.initials: Y
authors.lastname: Okabayashi
authors.forename: T
authors.initials: T
authors.lastname: Kitagawa
authors.forename: S
authors.initials: S
authors.lastname: Yamamoto
mesh_terms: D000328:Adult; D000535:Aluminum / Q000493:pharmacokinetics; D000863:Antacids / Q000494:pharmacology*; D000890:Anti-Infective Agents / Q000737:chemistry / Q000493:pharmacokinetics*; D002614:Chelating Agents / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D024841:Fluoroquinolones; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects*; D008274:Magnesium / Q000493:pharmacokinetics; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D015363:Quinolones / Q000737:chemistry / Q000493:pharmacokinetics*
chemical_list: D000863:Antacids; D000890:Anti-Infective Agents; D002614:Chelating Agents; D024841:Fluoroquinolones; D015363:Quinolones; D000535:Aluminum; D008274:Magnesium; C053091:lomefloxacin