Vinpocetine has been compared with 3 structurally related drugs for activity in protecting mice from hypoxia-induced lethality upon i.p. administration. In order of potency, vinpocetine (ED50 = 16.6 mg/kg), 1-eburnamonine (ED50 = 21.0 mg/kg), vinconate (ED50 approximately 25 mg/kg), and vincamine