Flesinoxan, a full 5-HT1A, receptor agonist, was administered (4–8 mg) to treatment-resistant depressed patients in an open study. Safety and tolerance of the substance appeared satisfactory. Headache, dizziness and nausea were the most frequently reported side effects. The observations suggested that flesinoxan is an antidepressant agent and that it may be of particular value in some difficult, treatment-resistant depressions. Based on these observations, a double-blind, placebo-controlled evaluation of flesinoxan's efficacy appears warranted