after three successive intravenous injections of propranolol , 0.5 mg/kg , had reduced the heart rate by 25 % , a fourth dose had no further negative chronotropic action , but amiodarone , 10 mg/kg intravenously , at this point reduced the heart rate by 23 % .3 .
C1372752
negative chronotropic
C0002598
amiodarone