Effect of ocular pigmentation on pilocarpine pharmacology in the rabbit eye. II. Drug response

Abstract

The time course of the miotic response of pilocarpine in albino and pigmented rabbit eyes was studied after ocular application of 0.11. 0.43, 0.85 and 2.30 mg doses in eye drops and 0.85 and 2.30 mg doses in polymer matrices. When administered in eye drops ocular pigmentation delayed the onset of the peak effect of the 3 smallest pilocarpine doses. The magnitude of the peak effect was lower in pigmented than in albino eyes after 0.11 and 0.43 mg doses, but equal after larger doses. Ocular pigmentation increased the relative biophasic availability of 0.85 and 2.30 mg doses of pilocarpine. This was due to the slower elimination rate of pilocarpine from pigmented tissues. The relative biophasic availability of 0.11 and 0.43 mg doses of pilocarpine was not affected by the ocular pigmentation, because of the opposite effects of lower peak effect and slower elimination rate on biophasic availability in pigmented eyes. The administration of pilocarpine in polymer matrices increased the relative biophasic availability of the drug. When administered in polymer matrices, pilocarpine showed a typical time course of prolonged pulse-entry of the drug into the eye.