Toxicity of intravitreal interferon alpha-2b in the rabbit.

OBJECTIVE

To investigate the toxicity of single doses of intravitreally administered interferon alpha-2b in the New Zealand white albino rabbit.

INTERVENTIONS: One eye each of six rabbits received an intravitreal injection of 1000, 10,000, 100,000, 500,000, 1 million or 2 million units of interferon alpha-2b reconstituted in 0.1 mL of balanced salt solution. The fellow eye of the first three rabbits received an intravitreal injection of the same volume of balanced salt solution.

OUTCOME MEASURES: Media opacities, toxic effects to the retina, optic nerve or other ocular structures.

RESULTS

The injection of 2 million units of interferon alpha-2b elicited an immediate dense vitreous haze that largely cleared within 24 hours as well as numerous intraretinal hemorrhages that were no longer visible 7 days after injection. Histopathological study of this eye 14 days after injection showed a diffuse mixed inflammatory cell infiltrate with retinal vacuolation and ganglion cell dropout. In the remaining eyes, to dosages of 1 million units, the agent produced no clinically or pathologically evident toxic ocular effects.

CONCLUSIONS

Interferon alpha-2b appears to be safe and well tolerated up to dosages of 1 million units.