Iontophoresis of gentamicin into aphakic rabbit eyes. Sustained vitreal levels.

The authors evaluated the intraocular penetration of gentamicin (50 mg/ml) into aphakic rabbit eyes following anodal iontophoresis (0.75 mA for 10 min). Gentamicin levels were determined at 0.5, 4, 8, 16, and 24 hrs after iontophoresis (n = 6 eyes for each time) using an agar diffusion bioassay. Peak levels of 72.04 +/- 6.1 (means +/- SE) micrograms/ml for the corneas and 77.8 +/- 3.0 micrograms/ml for the aqueous humor were obtained at 30 min after iontophoresis. The peak vitreous level was 10.4 +/- 0.4 micrograms/ml, which was found at 16 hrs after iontophoresis. Therapeutic levels of 6.2 +/- 3.0 micrograms/ml were still present in the vitreous humor 24 hrs after iontophoresis. Iontophoresis appears to be an effective noninvasive method for delivering therapeutic levels of gentamicin into ocular tissues and fluids of the aphakic rabbit eye.