Pharmacodynamic effects of pilocarpine eye drop enhanced by decreasing its volume of instillation

Previous studies have proved that as the volume of the drug solution instilled into the eye is decreased, the fraction of the dose absorbed into the ocular tissue is increased and the adverse drug reactions lowered. The present study investigated the acute effects of different drop volumes (10 microliters, 20 microliters, 40 microliters, and 80 microliters) of pilocarpine nitrate (2%) on pupil diameter, heart rate, and adverse reaction profile, in 12 healthy human volunteers. The drop volumes of 10 microliters and 20 microliters produced more miosis and less side effects than 40 microliters and 80 microliters drop volumes. This may be due to more penetration of the drug into the ocular tissue and less drainage into the nasolacrimal system.