Verapamil (ver AP a mil) treats high blood pressure and prevents chest pain (angina). It may also be used to treat a fast or irregular heartbeat (arrhythmia). It works by relaxing the blood vessels, which helps decrease the amount of work your heart has to do. It belongs to a group of medications called calcium channel blockers. This medicine may be used for other purposes; ask your health care provider or pharmacist if you have questions.