Toxic effects were observed in two healthy patients who received cocaine intranasally before dacryocystorhinostomy. One patient suffered an additional reaction to intranasally administered phenylephrine (Neo-Synephrine) hydrochloride. Because cocaine blocks uptake of catecholamines and has a sympathetic potentiating effect, its use is dangerous in patients with hypertensive cardiovascular disease or in conjunction with sympathomimetic or alpha-modifying drugs. Use of dilute solutions carefully measured for select patients is mandatory. The total dose of cocaine should not exceed 3 mg/kg.