Benactyzine is an
anticholinergic agent which has been used in past years in psychiatry, but is little used today. It has central and peripheral
anticholinergic effects, and when administered intramuscularly, it has a rapid onset of action. This may make it useful as an
antidote for
organophosphate poisoning, in spite of side-effects such as deficits of short term memory, concentration, and attention. As an
anticholinergic drug it could also be expected to produce vision changes by its action on the intraocular musculature controlling the pupil and lens accommodation. We tested the
drug on six volunteer subjects to establish the visual side-effects of intramuscular administration. We found that it reduced static and dynamic visual acuity, increased pupil size, reduced amplitude of accommodation and contrast sensitivity, while having little or no effect on glare recovery, color vision, intraocular pressure, stereoacuity, oculomotor tracking, and distance
heterophoria.
Benactyzine produced reductions in visual performance for up to 3 h and had the greatest effects on functions which have significant cognitive components. The present results suggest that the
drug is unsuitable for treatment for oganophosphate
poisoning when continuous performance is required, although a definitive test of ths suggestion would require that performance should be tested when
benactyzine and the
organophosphate of interest were combined.