A drug used to treat high blood pressure, including before surgery for pheochromocytoma, and to treat chest pain (angina), abnormal heartbeat (arrhythmia), and several other conditions. It is also being studied in the treatment of other conditions and types of cancer. Inderal blocks certain receptors on nerve cells and causes blood vessels to relax and dilate (widen). This allows blood to flow more easily and lowers blood pressure and heart rate. Inderal contains the active ingredient propranolol hydrochloride. It is a type of beta blocker.