The Role of the Cornea in the Biologic Response to Pilocarpine

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Abstract

Studies were conducted to elucidate the role of the cornea in pilocarpine penetration. Penetration characteristics were investigated utilizing an in situ isolated rabbit cornea preparation in which the pilocarpine was administered via a hydrophilic polymer delivery system. This delivery mode was chosen because the amount of drug delivered to the cornea could be quantitated through elution studies and also because it could be reproduced in vivo for a better comparison of available pilocarpine with rabbit miotic response. In vivo studies involved determination of the miotic response of alert rabbits to pilocarpine under controlled conditions. The results suggest that the rabbit cornea accepts all of the pilocarpine exposed to its epithelial surface. However, the rate at which it is released across the endothelial surface is slower and dependent upon the quantity of pilocarpine delivered to it. As a consequence, pilocarpine apparently accumulates within the cornea, which serves as a drug reservoir. This relationship has not been demonstrated previously in the literature. The relationship between the available pilocarpine, as demonstrated in situ and the miotic response, as determined in vivo has not been clearly defined.