Tenormin 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. Stress hormones (such as adrenaline) attach to these receptors and cause 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).
Tenormin helps to block a specific type of beta receptor called beta-1 receptors. By blocking beta-1 receptors, the drug causes the reverse effect of these stress hormones. It decreases heart rate and both systolic and diastolic blood pressure, as well as the workload of the heart. This means that the heart requires less blood and oxygen to work properly.
Tenormin 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 other similar conditions.
By lowering blood pressure, Tenormin can decrease the risks that accompany long-term high blood pressure (see Effects of High Blood Pressure). By decreasing the workload of the heart, it can also decrease symptoms of angina, including chest pain. Finally, although the exact mechanism is not known, the drug can increase survival in people who have just had a heart attack.