Metoprolol is a member of a class of drugs know as beta blockers and is often prescribed by doctors to treat various conditions such as high blood pressure and rapid heart rates. Like all beta blockers, metoprolol has the ability to block the effects of certain natural chemicals that trigger stress responses in the body. By preventing the body from reacting to stress in a normal way, such as with an increased pulse when frightened, metoprolol can help to protect individuals for whom sudden increases in blood pressure or excessive heart rates might be dangerous. In the United States it is marketed under the brand names Toprol-XL® and Lopressor®. Generically, it is sold simply as metoprolol.
In the body, metoprolol acts as a beta-1 inhibitor, which blocks the receptors in the heart and kidneys that receive and react to adrenaline. As a result, when an individual taking the drug becomes frightened or excited, and adrenaline is released into the body in a fight-or-flight response, the person’s heart will experience little or no reaction to the adrenaline. This prevents the individual’s heart from instantaneously attempting to beat faster and harder, which can result in heart damage or even death in those who have compromised cardiac systems.
The ability to block adrenaline in the heart has made metoprolol useful as an off-label treatment for some conditions not directly heart-related, such as to help people who experience certain types of anxiety disorders. By preventing increased heart rates and blood pressure in response to an adrenaline release during an anxiety attack, the physical stress experienced by an individual is greatly reduced, allowing him or her to continue to function in a relatively normal fashion. For the same reasons, the drug is also useful to assist individuals not prone to anxiety attacks but who must be able to function normally in extremely stressful situations, such as soldiers engaged in combat.
Other off-label uses for metoprolol are usually related to the vascular system. For example, it can lessen the effects of stress on blood pressure, which can help prevent migraine headaches. The drug is also considered to be useful in treating vasovagal syncope episodes, which is fainting caused by a sudden change in blood flow or blood pressure to the brain.
There are a number of side effects related to metoprolol. The most common, and least serious, include drowsiness, dizziness, fatigue, and a slower than normal heart rate. More serious reactions to the drug include excessively slow heart rates, severe dizziness, fainting, trouble breathing, shortness of breath, and unusual mood changes. Individuals experiencing serious reactions should consult their doctors immediately, as should those experiencing less serious, but persistent, side effects.