Atenolol is part of a class of drugs called beta-adrenergic blocking agents, or beta blockers for short. As the name implies, beta blockers work by blocking beta receptors in the body. Beta receptors are located in a number of places within the body, including the heart and blood vessels. Adrenaline attaches to these receptors and causes certain reactions in the body, such as an increase in:
- Heart rate
- The force with which the heart pumps blood
- Blood pressure (both systolic and diastolic blood pressure).
Atenolol helps to block a specific type of beta receptor called beta-1 receptors. By blocking beta-1 receptors, the medication causes the reverse effect of adrenaline. It decreases heart rate, systolic and diastolic blood pressure, and the workload of the heart. This means that the heart requires less blood and oxygen to work properly.
Atenolol is a beta-1 selective (or cardioselective) beta blocker. This means that it mostly blocks beta-1 receptors, especially at normal doses. However, it can block beta-2 receptors in the lungs to some extent, especially at higher dosages. This can lead to breathing problems, especially in people with asthma or similar conditions.
By lowering blood pressure, atenolol can decrease the risks that accompany long-term hypertension (see Effects of High Blood Pressure). By decreasing the workload of the heart, the drug can also decrease symptoms of angina, including chest pain. Finally, although the exact mechanism is not known, atenolol can increase the survival in people who have just suffered a heart attack.