Propranolol is a prescription beta blocker that increases blood flow and decreases blood pressure. It is therefore widely used for the treatment of high blood pressure, chest pain, as well as to improve survival after a heart attack. Inform your doctor of any other medicines you are taking at the moment, including but not limited to high blood pressure medicines, medicines for the treatment of colds, vitamins, drugs for migraine headaches, asthma or allergies meds, pain medications, reserpine, and drugs for heart disease. Watch for any side effects that seem serious to you. For example, if you experience lightheadedness, diarrhea, vomiting, rash, upset stomach, excessive tiredness, insomnia, constipation, or dizziness - there is no reason to get worried, as these are the mild effects most likely to disappear on their own as your body adjusts to the dosage and schedule of taking propranolol. You can continue taking propranolol if you notice these mild side effects: constipation, excessive tiredness, insomnia, rash, diarrhea, dizziness, upset stomach, vomiting, and lightheadedness.