Propranolol (INN) is a sympatholytic nonselective beta blocker. It is used to treat high blood pressure, a number of heart dysrhythmias, thyrotoxicosis, and essential tremors. It is used to prevent migraine headaches, and to prevent further heart problems in those with angina or previous heart attacks. It comes in both oral and intravenous forms.It should not be used in those with an already slow heart rate and most of those with heart failure.