AIM: To determine the pharmacokinetics and distrubution of methylprednisolone sodium succinate(MPS)and its metabolic product methylprednisolone(MP)in eye tissues and blood plasma after MPS periocular injection in rabbits.

METHODS: After periocular injection of MPS 10mg, the concentrations for MP and its prodrug conmpound were quantified at different time points using mass spectrum-liquid chromatography in plasma and ocular tissues-slera, choroid and retina, vitreous, iris, aqueous humor, lens and optic nerve.

RESULTS: After periocular injection, the time of maximum concentration(T_max)for MPS in ocular tissues was 0.25 to 1h, in blood plasma was 0.25h. Tmax for its metablite MP in ocular tissues was 0.5 to 6h, in blood plasma was 0.5h. The maximum MPS and MP concentration(C_max)and the area under the curve(AUC_0-t)in ocular tissues from high to low in turn was sclera, optic nerve, the choroid and the retina, iris and lens. The drug concentration of lens was not only the lowest among all tissues, but also much lower than others by far the content, and its mean residence time was the longest.

CONCLUSION: Periocular administration of MPS is an effective way to intraocular drug transmission. It achieves a satisfactory drug distribution in sclera, optic nerve, choroid and retina. It is not easily absorbed by lens.