Topical vs systemic gentamicin penetration into the human cornea and aqueous humor
M. S. Insler, C. J. Helm and W. J. George
Twenty-two patients undergoing penetrating keratoplasty received either
topical fortified gentamicin (13.6 mg/mL) or a loading dose of
intramuscular gentamicin before surgery. Cornea and aqueous humor samples
were obtained and assayed by radioimmunoassay for gentamicin. In the
topical group, the average gentamicin levels in the cornea and aqueous were
16.2 micrograms/g and 0.3 microgram/mL, respectively. Parenteral drug
levels were less variable and averaged 6.1 micrograms/g in the cornea and
0.4 microgram/mL in the aqueous. Although this study demonstrates that
parenteral therapy can be used to deliver adequate drug levels to the
cornea, it requires far more antibiotic and subjects the patient to
potentially toxic systemic side effects. Therefore, topical administration
is the preferred route of delivery of antibiotic to the cornea.
