There are some situations where propranolol, like all medicines, should be used with caution or would not be recommended. This might be the case, for example, in people under 18; people with asthma, COPD, or other breathing problems; diabetes; some heart conditions including heart failure, angina, peripheral vascular disease, or heart rhythm problems; and low blood pressure. It will also apply to people prone to low blood sugar and those who are allergic to any of the active or inactive ingredients.. BETA This is a trial service — your feedback (link opens a new window) will help us to improve it.. Propranolol is classed as a “beta blocker”. Medicines in this category have been used for many years by doctors to treat and prevent many different conditions, including high blood pressure, angina, irregular heartbeat, anxiety, and migraines..