Clearance of intravitreal fluorouracil. Normal and aphakic vitrectomized eyes.

The ocular pharmacokinetics of 5-fluorouracil (5-FU) after intravitreal administration in the rabbit are described for the first time. Following a 1 mg intravitreal injection of C-14 labeled 5-FU in the phakic nonvitrectomized eye, a peak level of 664 micrograms/ml is achieved which declines to 7.8 micrograms/ml at 24 hours. For the aphakic vitrectomized eye comparable values are 669 micrograms/ml at 0.1 hour and 0.21 micrograms/ml at 24 hours. 5-FU is cleared more than two times more rapidly in aphakic vitrectomized eyes than normal eyes during the first 12 hours following injection. Following this, when the actual concentrations are relatively low, the rate of clearance appears relatively similar for both groups of eyes. Although it is difficult to extrapolate from previous in vitro results, potentially therapeutic vitreous concentrations are present in normal rabbit eyes for up to 72 hours following a single intravitreal injection.