Interaction of the fluoroquinolone antimicrobial agents ciprofloxacin and enoxacin with liposomes.

The interaction between ciprofloxacin and enoxacin and phospholipid-containing bilayers was examined as the initial step in transmembrane diffusion processes. By using cosedimentation, maximal association of liposomes and 14C-labeled enoxacin and ciprofloxacin was detected at acidic and neutral pHs. Aqueous solubility of ciprofloxacin, enoxacin, and norfloxacin was poorest at neutral pH and greater at alkaline or acidic pHs. These investigations suggest that the interaction occurs because of ionic and hydrophobic forces and is nonsaturable up to 20 micrograms/ml.