Objective: To study the acute toxicity of total flavonoid from Scutellaria amoena in mice and its effect on experimental arrhythmia induced by aconitine in rats. Method: The acute toxicity of the flavonoid was investigated by Blisss method. The anti-arrhythmia efftect of the flavonoid was determined by ECG of rats and of guinea pigs. Result: The flavonoid showed some toxicity on mice

but its median lethal dose (LD50 4.438 8 g ·kg-1) keeps away from effective median dose(20 mg ·kg-1) of anti-arrhythmia activity experiment. It could obviously increase the threshold dose of ventricular premature beats(VP)

ventricular fibrillation(VF) and cardia ventricular arrest(CA) induced by aconitine in rats and shorten the duration of ventricular arrhythmia induced by adrenaline in guinea pigs with dose-dependent manner. Conclusion: The flavonoid from S. amoena has very little toxicity in mice

but obvious protective effect on arrhythmia models in animals.