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Side effects of Metoprolol

by egpat         30 May 2024

Metoprolol is a beta blocker, which can be clearly identified by its suffix "-olol." Among the beta blockers, we can have two types: cardio-selective and cardio-non-selective. Here, metoprolol is a cardio-selective beta blocker that selectively acts on beta-1 receptors located in the cardiac system. Metoprolol can be particularly used for cardiovascular disorders like angina, where this drug can reduce cardiac pain by reducing cardiac work.

Similarly, this drug can be used in conditions like heart failure, where metoprolol reduces cardiac work, thereby increasing cardiac efficiency. In the treatment of heart failure, many of the beta blockers are contraindicated because they reduce the force of contraction, but metoprolol can still be used in conditions like heart failure as it reduces cardiac work and increases cardiac efficiency.

Another clinical use of metoprolol is in the treatment of hypertension, where this drug can reduce the blood pressure. In this way, metoprolol has various clinical uses, all of which are related to the cardiovascular system. It is highly selective for beta-1 receptors expressed in the heart, but it can still show a few side effects and affect various organs like the central nervous system, lungs, and even the eye. Hence, it can produce various side effects when it is indicated for cardiovascular disorders. Here in this article, let us explore the eight important side effects of metoprolol, how they are produced, and how they can be managed.

1. Dizziness

Metoprolol can enter the brain and affect the functionality of the CNS. Particularly, it can produce some depressive effects. Therefore, it can produce some lightheadedness and dizziness in people. This is particularly observed while changing posture, either from the lying position to the standing position or from the lying position to the sitting position. These effects are more pronounced in the first few weeks of the therapy. That's why, in the early days of the use of metoprolol, care should be taken while standing or sitting. This dizziness can be increased with other drugs co-administered with metoprolol.

This metoprolol is supplied in its ester form, metoprolol succinate. This medication is available as a capsule or an extended-release capsule; it's called the ER capsule or XL capsule. From this capsule, the drug is slowly released, but the release of the drug from this medication may be modified by other conditions. Alcohol can increase the release of this medication from this extended-release capsule when taken simultaneously.

So instead of slow release, metoprolol can be released very rapidly from this capsule, which may increase the side effects produced by this medication. That's why, in the presence of alcohol, we can observe more dizziness, and even alcohol itself can produce some dizziness. That's why, along with metoprolol, an intake of alcohol is not recommended.

2. Bradycardia

Metoprolol is a cardioselective beta-blocker used for the treatment of hypertension as well as tachycardia. It can block the beta-1 receptors located on the heart, which results in a decrease in the heart rate. So with the use of metoprolol, we can observe a slowing of the heart rate, which is commonly known as bradycardia, and this bradycardia may also increase dizziness in people. In a few of the cases, we can also observe some irregular heartbeats because of the slowing of the heart rate.

This is commonly observed in many people because metoprolol acts directly on the heart and can reduce the force of contraction as well as the rate of contraction. Under therapeutic doses, this bradycardia is not that troublesome, but when this metoprolol is used at a very high dose, this medication can produce some significant slowing of the heart rate.

3. Fatigue

Even though it has high cardioselectivity, metoprolol can also act on beta-2 receptors, which are located in different types of organs. Among them, the blood vessels supplying the skeletal muscle are more important. Normally, these beta-2 receptors are responsible for vasodilation, but they can increase the blood supply to the skeletal muscle. Now, metoprolol can block these beta-2 receptors, which can result in a decreased blood supply. This may result in muscle weakness and fatigue. Some unexpected weaknesses can be observed.

Similarly, metoprolol can also act on the heart and block beta-1 receptors, which reduces the heart rate and decreases blood supply to the skeletal muscle. With the use of metoprolol, patients may experience some unexpected tiredness and muscle weakness.

4. Breathing problem

Metoprolol shows some less breathing problems compared with non-selective beta blockers, but still, at higher doses, the selectivity may be lost. Metoprolol can also act on the bronchial smooth muscle, and it can block beta-2 receptors. Normally, these beta 2 receptors are responsible for bronchodilation, but when they are blocked, it results in bronchoconstriction, leading to shortness of breath and trouble breathing.

Because of its greater cardio selectivity, these side effects are rarely observed with metoprolol, but in people with any bronchospasm, these side effects may be more enhanced, and in people with severe bronchospasm, metoprolol is contraindicated.

5. Pruritus

Epinephrine is one of the neurotransmitters in the sympathetic system. This epinephrine can block the activity of mast cells, so it can reduce degranulation, thereby reducing the allergic response. The mast cell mainly stores one of the mediators, histamine, which is responsible for allergy. This allergic response is blocked by epinephrine.

Metoprolol can block the action of epinephrine so that the degranulation of mast cells can be increased, resulting in the release of histamine. This histamine can produce various allergic responses, resulting in itching sensations and skin rashes. So with the use of metoprolol in the long term, we may observe some pruritic conditions.

6. Blurred vision

Metoprolol can produce some blurred vision, increased sleepiness, and somnolence in people. It can also produce a state of confusion and dry mouth. All these side effects are commonly observed with metoprolol.

7. Hypotension

Since metoprolol acts on the heart, it can block beta-1 receptors. When these receptors are blocked, it results in a decrease in the heart rate. As the heart rate is reduced, it can reduce the afterload and pumping pressure. This results in a reduction in blood pressure. In this way, metoprolol can reduce blood pressure by indirectly reducing the heart rate.

Therefore, with the use of metoprolol, a drop in blood pressure can be observed. Both systolic and diastolic blood pressures can be reduced. A drop in pulse rate is also observed. So with a higher dose of metoprolol, significant hypotension can be produced. That's why it's always better to start with a low dose in order to treat cardiovascular conditions.

8. Mood changes

Even though this is a rare side effect, metoprolol can produce some depressive effects on the CNS. With the use of metoprolol, people may have some hallucinations, either auditory or visual hallucinations. They may have some nervousness, some insomnia, or a lack of sleep. Rarely, it can also produce some depression in people.

All these are even rare conditions, but they can be observed with very prolonged use of metoprolol.

So these are the eight important side effects of metoprolol that are commonly observed. Here is a video explaining all these points.