OCULAR EFFECTS OF HYOSCINE IN DOUBLE DOSE TRANSDERMAL ADMINISTRATION AND ITS REVERSAL BY LOW-DOSE PYRIDOSTIGMINE

The potential of low dose (30 mg t.i.d) pyridostigmine to reduce the o cular side effects of double dose transdermal controlled release hyosc ine was evaluated by the study of near visual acuity, accommodation am plitude and pupil diameter in a placebo controlled, double masked stud y. We studied 47 healthy men (age 18-21 yr) in 3 groups: 16 assigned t o placebo hyoscine and placebo pyridostigmine, 15 assigned to double d ose hyoscine and placebo pyridostigmine, and 16 to double dose hyoscin e and pyridostigmine. Subjects were tested during 48 h of treatment an d 48 h of washout period. Blood cholinesterase inhibition level and am ount of hyoscine released from the patches were used as parameters of reliability. Difference between groups was assessed using change from baseline scores. Double dose hyoscine caused decrease in near visual a cuity to a mean of 14/18. Accommodation amplitude was decreased in the double dose transdermal hyoscine group from 9.19 +/- 1.04 to 4.83 +/- 1.97 diopters of accommodation. This decrease was significant when co mpared to the placebo group (p < 0.05) and to the pyridostigmine-prote cted group (p < 0.05). Pyridostigmine, however, did not significantly change the hyoscine-induced mydriasis of 1.47 +/- 0.15 mm change from baseline (p < 0.05). These results suggest that pyridostigmine adminis tration may be beneficial in shortening recovery time when near vision impairment is experienced following single and double dose transderma l hyoscine administration.