Distribution of morphine in the eye tissues and fluids of rabbits after systemic administration and after transfer via corneal grafting.

To determine whether corneas from animals receiving morphine could be used for grafting, rabbits were given a single intravenous injection of tritium-labelled morphine and killed 10 minutes later. Of the drug entering the eye, 12% was found in the cornea, 36% in the retina and optic nerve, 29% in the uveal tissues, 8% in the aqueous humour, 8% in the choroid, 4% in the vitreous humour and 2% in the lens. Another group of rabbits then received full-thickness corneal grafts from rabbits treated with morphine. The grafts contained the drug for up to 21 days after transplantation. From the graft bed the agent dispersed into the different solid ocular tissues and intraocular fluids. None of the grafts failed, and none of the recipients' eyes showed any adverse reaction. In-vitro tests showed that the amount of morphine found in the cornea and the aqueous humour of the donor did not have any significant effect on cell division or protein synthesis of the corneal cells. Higher concentrations of the drug, however, decreased both cell division and protein synthesis.