Calaptin 240 SR Tablet works by relaxing blood vessels so that blood can flow more easily around your body. This lowers your blood pressure and reduces your risk of having a stroke, heart attack, or kidney problems in the future. It must be taken regularly as prescribed to be effective. You do not usually feel any direct benefit from taking this medicine, but it works in the long term to keep you well. Do not stop taking this medicine without your doctorâs advice, even if you feel well.