Potentiating effects of caffeine on the cardiovascular teratogenicity of ephedrine in chick embryos.

Ephedrine was administered to 3-day chick embryos (Hamburger-Hamilton developmental stage 19) together with caffeine at doses where each agent alone caused minimal embryotoxicity. Embryos were examined for malformations on day 14 of incubation. The teratogenicity of ephedrine in the chick cardiovascular system was significantly potentiated by caffeine at a dose as low as 0.5 mumol (0.1 mg/egg; 2 mg/kg egg).