The responses of the human eye to the intraocular administration of the adrenergic neurone blocking drugs guanethidine sulfate and debrisoquin sulfate have been investigated by photographically recording the pupillary changes. After protracted treatment with local guanethidine sulfate (100 mg/ml), the mydriatic action of phenmetrazine hydrochloride, amphetamine sulfate, hydroxyamphetamine hydrobromide, ephedrine hydrochloride, and tyramine hydrochloride was abolished and that to methoxamine hydrochloride, epinephrine bitartrate, and phenylephrine hydrochloride potentiated. Following chronic debrisoquin (20 mg/ml) the mydriatic responses to phenylephrine and ephedrine were potentiated. These results indicated that guanethidine exhibits pharmacological actions which parallel postganglionic sympathectomy, while debrisoquin mimicks preganglionic sympathectomy.
Sneddon JM, Turner P. The Interactions of Local Guanethidine and Sympathomimetic Amines in the Human Eye. Arch Ophthalmol. 1969;81(5):622-627. doi:10.1001/archopht.1969.00990010624005