PLASMA-CONCENTRATIONS AND OCULAR EFFECTS OF CYCLOPENTOLATE AFTER OCULAR APPLICATION OF 3 FORMULATIONS

1 Eight volunteers received in randomized order two 30 mul drops of ei ther 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 radio receptor assay. 2 Peak plasma drug concentrations of about 3 ng ml-1 o ccurred within 30 min after all formulations. Occasionally, a second c oncentration peak in plasma, probably reflecting drug absorption from the gastrointestinal tract, was seen after 2 h. The mean elimination h alf-life of cyclopentolate was 111 min when all subjects and formulati ons were considered together. There were no statistically significant differences between the formulations with respect to the time-course o f plasma drug concentration. 3 The maximal mydriatic effect was reache d within about 15 min and was maintained for several hours, often bein g 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 ne ar-point of vision being 9 to 10 dioptres. The cycloplegic response wa s more intense after one of the polygalacturonate complexes, especiall y at later time points.