Atenolol belongs to a group of medicines called beta-blockers. It blocks the action of the nervous system on the heart and reduces the force of heart muscle contraction and lowers blood pressure. By reducing the heart rate and the force of muscle contraction, atenolol reduces heart muscle oxygen demand. Because angina occurs when oxygen demand of the heart exceeds supply, atenolol is helpful in treating angina.
Nifedipine belongs to a group of medicines called calcium-channel blockers.
These medicines block the transport of calcium into the smooth muscle cells lining the heart blood vessels and other blood vessels of the body. Since calcium is important in muscle contraction, blocking calcium transport relaxes the muscles of the blood vessels and makes them wider. Relaxing the muscles lining the blood vessels of the rest of the body lowers the blood pressure. Reducing heart burden lessens the heart muscle's demand for oxygen, and further helps to prevent angina in patients with coronary artery disease. It is very important to take medicines as often as your doctor has told you to, even if you do not feel ill.