Gentamicin, norfloxacin and lysozyme concentration in human tears: in vivo and in vitro study

Hen's egg lysozyme (HEL) activity was measured in vitro with gentamicin and norfloxacin by a turbidimetric technique. Gentamicin at the concentration of 10(-3) M inhibited HEL activity by 39%, while 10(-3) M norfloxacin did not affect HEL activity. However, an in vivo study in healthy persons did not show any significant statistical difference in tear lysozyme activity when 0.3% gentamicin or 0.3% norfloxacin were topically applied.