Abstract
Aim: In this study, we aimed to investigate and compare the effect of topical administration of quaternary amines (QA) to tertiary amines (TA) on the pupil size of rabbit eyes.
Material and Methods: TA (Pilocarpine and Physostigmine) and QA (Neostigmine and Pyridostigmine) muscarinic agonists were used as pupil constrictors, while TA (Tropicamide and Cyclopentolate) and QA (Hyoscine-N-butylbromide, Ipratropium, Isopropamide, and Hexahydro-adephenine) muscarinic antagonists were used as pupil dilators. Serial dilutions of these drugs (4 concentrations for each) were prepared in distilled water from their preparations available on the market. Their effect on pupil size was measured at 0, 15, 30, 45, 60, 120, and 180 minutes (n=4). Linear plots of the effects of various concentrations were drawn by MS-Excell. The onset and duration of action of QA were compared with the corresponding TA.
Results: The onset of action of pupil constriction with TA and QA muscarinic agonists was between 15-30 minutes and the effect lasted for 120-180 minutes. The onset of action of pupil dilatation with TA and QA was also between 15-30 min and effect lasted for > 180 minutes.
Discussion: This experimental study demonstrated that the extent of ionization of QA muscarinic agonists or antagonists did not influence their diffusion across ocular tissues cornea and conjunctiva. These drugs can be used topically for pupillary constriction or dilatation.