Calan SR is a brand name for the medication verapamil, which belongs to the class of drugs called calcium channel blockers. Calan SR 240mg tablets contain 240mg of verapamil hydrochloride as the active ingredient. This medication is primarily used to treat hypertension (high blood pressure), angina (chest pain), and certain types of arrhythmias (irregular heartbeats). Calan SR works by relaxing the blood vessels, which reduces the workload on the heart and increases blood flow and oxygen supply to the heart. It comes in the form of extended-release tablets that are taken orally.