Duration of therapeutic levels of intravitreally injected liposome-encapsulated clindamycin in the rabbit.

We investigated an intravitreal preparation of liposome-encapsulated clindamycin phosphate to determine the duration of therapeutic levels of the drug in the vitreous cavity. Twenty New Zealand albino rabbits were given an intravitreal injection of 750 micrograms/0.1 mL of encapsulated clindamycin (10 animals) or 800 micrograms/0.1 mL of nonencapsulated clindamycin (10 animals) and then were killed immediately or 6, 12, 24 or 48 hours later. The mean concentration of encapsulated clindamycin in the vitreous at 48 hours was 28.4 micrograms/mL, while that of nonencapsulated clindamycin at 24 hours was 2.3 micrograms/mL. The estimated elimination rate of nonencapsulated clindamycin was 3 hours, compared with approximately 10 hours for the encapsulated preparation. This drug delivery system warrants further investigation for possible use in humans.