Pholedrine is a hydroxymethylamphetamine. It is a sympathimimetric drug of low toxicity, which is of great value in conditions of hypotonia, collapse, and circulatory depression. Pholedrine was reported on in 1937 by several investigators, who described its vasopressor action in animals as more potent than that of ephedrine. The drug is grouped with hydroxyamphetamine because of its similarity in structure and hemodynamic pattern. Pholedrine, in small doses, potentiates epinephrine, but in large doses blocks its pressor effect. Pholedrine applied as eye-drops produces mydriasis that is greatly attenuated by guanethidine pretreatment and diminished in patients with postganglionic sympathetic nerve lesions. It might be used to diagnose Horner's syndrome.