Effect of thymoxamine on the human pupil.
The specificity of thymoxamine, an alpha-adrenoceptor antagonist was determined from in vitro organ bath studies using isolated preparations of canine saphenous and portal mesenteric veins. It was found that thymoxamine interacts mainly with postjunctional alpha-adrenoceptors. The miotic effects of topical thymoxamine hydrochloride were measured in normal human eyes using infrared pupillography. The effects of five different concentrations of thymoxamine were measured over time. Time-response and concentration-response relationships were calculated. The maximal pupillary response occurs at 60 min after instillation of the drug and has a half-life of 10 hr. The minimum effective concentration of thymoxamine is 0.01%, and the maximum effective concentration is 1.3%. Thymoxamine's properties could make it a clinically useful drug to diagnose angle-closure glaucoma, and also to reverse drug-induced mydriasis.
D000328:Adult; D000818:Animals; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005260:Female; D006207:Half-Life; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008642:Mesenteric Veins / Q000187:drug effects; D013948:Moxisylyte / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011680:Pupil / Q000187:drug effects*; D012501:Saphenous Vein / Q000187:drug effects; D013997:Time Factors; D014991:Xylazine / Q000494:pharmacology
D010656:Phenylephrine; D014991:Xylazine; D011433:Propranolol; D013948:Moxisylyte; D009638:Norepinephrine