In the present paper interactions between enrofloxacin and phosphatidy
lcholine, dipalmitoylphosphatidylcholine, and mixtures of these lipids
with cholesterol were studied by different techniques. Hydrophobic in
teractions were determined by differential scanning calorimetry, carbo
xyfluorescein leakage from liposomes, and compression isotherms of mix
ed monolayers. The penetration kinetics as well as the polarization ch
anges of the anilinonaphthalene sulfonate probe inserted into liposome
s were used to study the effect of the drug in the lipid polar head mo
tion. The drug was unable to form monolayers and compression isotherms
showed a low level of drug interaction with phospholipids. This was a
lso confirmed by differential scanning calorimetry measurements in whi
ch no change in the main transition temperature was observed but a sli
ght broadening of the peaks. However, a strong influence in the fluidi
ty of the polar part of the bilayers after incubation of liposomes wit
h enrofloxacin was found.