Effect of antacid on absorption of the quinolone lomefloxacin

Antimicrob Agents Chemother. 1992 Jun;36(6):1219-24. doi: 10.1128/AAC.36.6.1219.


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.

MeSH terms

  • Adult
  • Aluminum / pharmacokinetics
  • Antacids / pharmacology*
  • Anti-Infective Agents / chemistry
  • Anti-Infective Agents / pharmacokinetics*
  • Chelating Agents / chemistry
  • Chromatography, High Pressure Liquid
  • Fluoroquinolones*
  • Humans
  • Intestinal Absorption / drug effects*
  • Magnesium / pharmacokinetics
  • Magnetic Resonance Spectroscopy
  • Male
  • Middle Aged
  • Quinolones / chemistry
  • Quinolones / pharmacokinetics*


  • Antacids
  • Anti-Infective Agents
  • Chelating Agents
  • Fluoroquinolones
  • Quinolones
  • Aluminum
  • Magnesium
  • lomefloxacin