The objectives of these studies were to determine the amount and distribution of the aminoglycoside antibiotic amikacin delivered to rabbit eyes following transscleral iontophoresis and to determine the inter-study reproducibility of delivery over three identical studies. New Zealand White rabbits (N = 6 per dose group) were treated with a 200-mg/mL amikacin solution at 0, 2, 3 or 4 mA of (+) DC current for 20 minutes. Amikacin concentrations in eye tissues were highest with the 4-mA treatment. Concentrations for all three studies at this current were approximately 5.4, 40, 41, 343, and 92 mcg/g in the vitreous humor, anterior segment, non-treated hemisphere of the sclera, treated hemisphere of the sclera, and retina/choroid, respectively. These values were approximately 27, 50, 40, 10, and 13 fold greater than in the 0-mA control group and are well above the in vitro minimum inhibitory concentrations (MICs) for this drug. Inter-study reproducibility (measured as %CV) depended on the tissue type and treatment group and ranged from 8% for the retina/choroid to 51% for the anterior segment in the 4-mA group. Pretreatment with topical proparacaine hydrochloride local anesthetic did not affect amikacin delivery and total drug delivered was not affected by delivery time for the same total charge administered. Therapeutically relevant amounts of amikacin were delivered into eye tissues in a reproducible and controllable manner.
