Quindonium is azaestrone derivative patented by Shionogi & Co., Ltd. As an anti-inflammatory agent. Quindonium acts as a bradycardic agent which disrupts regular sinus rhythm in barbiturate-anesthetized dogs. Sinus bradycardias were interrupted by periods of sinus acceleration during which the disturbances in the lead II electrocardiogram were either minor or absent. The rate and rhythm changes were resistant to vagotomy or atropine, propranolol, and pentolinium. Propranolol enhanced the responses and precipitated arrhythmias in resistant animals; carotid sinus denervation had the opposite effect. Prophylactic administration of Quindonium (10 mg/kg) 15 minutes before hemorrhage produced a significant increase in the survival rate of dogs exposed to hemorrhage stress