Plasma concentrations and ocular effects of cyclopentolate after ocular application of three formulations.

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Abstract
1. Eight volunteers received in randomized order two 30 microliters drops of either 1% w/v cyclopentolate hydrochloride or a corresponding amount of cyclopentolate polygalacturonate in saline or in acetate buffer in one eye. Cyclopentolate concentrations in plasma were measured by a radioreceptor assay. 2. Peak plasma drug concentrations of about 3 ng ml‐1 occurred within 30 min after all formulations. Occasionally, a second concentration peak in plasma, probably reflecting drug absorption from the gastrointestinal tract, was seen after 2 h. The mean elimination half‐life of cyclopentolate was 111 min when all subjects and formulations were considered together. There were no statistically significant differences between the formulations with respect to the time‐course of plasma drug concentration. 3. The maximal mydriatic effect was reached within about 15 min and was maintained for several hours, often being 1/3 of its peak value after 30 h. Similarly, an intense cycloplegic response was achieved within a few minutes, the peak changes in the near‐point of vision being 9 to 10 dioptres. The cycloplegic response was more intense after one of the polygalacturonate complexes, especially at later time points.

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