Pharmacokinetic investigation of fusidic acid 1% viscous eye drops in healthy volunteers.

The biological half-life of fusidic acid was measured in tear fluid samples from the inferior fornix of 14 healthy volunteers after instillation of one drop of viscous fusidic acid eye drops. The study comprised four test days separated by six days of wash-out. On the first test day the concentrations of fusidic acid were measured 1 h after installation, on the second test day 3 h after, on the third test day 6 h after, and on the last day 12 h after instillation. The median fusidic acid concentrations in the tear fluid were 15.7 micrograms/ml, 15.2 micrograms/ml, 10.5 micrograms/ml and 5.6 micrograms/ml on the four days. This corresponds to a biological half-life of 7.3 h. Some of the volunteers reported mild local discomfort lasting a few minutes.