Metoprolol is a Beta-1 selective adrenergic blocking agent. It widely falls in the group of drugs named as Beta blockers. Other drugs included in this group are Atenolol, Betaxolol, Acebutolol, Celiprolol, Bisoprolol, Esmolol and Nebivolol. All these drugs are Beta 1 selective drugs. Metoprolol is marketed all over the world with different brand names like Lopressor, Mepressor, betaloc, Neobloc, Selokeen etc. Beta 1 receptors are predominantly located in the heart and eye. In heart Beta 1 receptors mediate the heart rate and contractility. Increased stimulation of these receptors lead to increased heart rate and increased contractility. So, Metoprolol inhibits the Beta 1 receptors in the heart and decreases the heart rate as well as contractility of the heart.
What is Metoprolol used for?
Metoprolol is commonly used for:
- Myocardial infarction – can be used for both acute myocardial infarction and secondary prevention of myocardial infarction. It prevents remodeling of the ventricle
- Angina – effective in all the types of angina as it decreases the workload on the heart
- Ventricular tachycardia
- Supraventricular tachycardia
- Chronic heart failure
- Migraine – used for the acute management and prevention of migraine
- Thyrotoxicosis – adjunct to antithyroid drugs in order to inhibit the thyrotoxic effects mediated through Beta 1 receptors
- Long QT syndrome
- Social phobias
Common side effects of Metoprolol
Metoprolol has a better safety profile as compared to other beta blockers because of its Beta 1 selectivity. Most of the side effects of beta blockers occur due to Beta 2 receptor blockade.
Common side effects of Metoprolol are:
- Light headedness or dizziness – Metoprolol decreases the blood pressure, so extended action may cause light headedness in some individuals
- Unusual fatigue and tiredness
- Drowsiness – patients using Metoprolol may remain drowsy during the day. So, they must not drive or handle machinery during the treatment
- Insomnia – in some individuals disturbed sleep pattern or even difficulty sleeping is also observed during the use of this drug
- Unusual dreams – night mares and vivid dreams are one of the most common side effects of Metoprolol occurring in any age group
- Neuropsychiatric disorders – Metoprolol can cause severe depression in absolutely healthy and normal individual. Moreover, mood swings alternating between happy and sad moods is also observed frequently
- Lack of coordinated movements – Ataxia (lack of coordination)
- Gastrointestinal intolerance – it may cause nausea, vomiting, stomach cramps, constipation, heart burns and flatulence
- Dryness of mouth – thirst is increased by the use of this drug and most of the time there is a feeling of dryness in the mouth
- Skin allergies – allergic reactions manifest as swelling and rash on the skin and severe itching. It may be accompanied by dizziness
- Cold peripheries – due to mild beta 2 blockade effect, Metoprolol constricts the peripheral arteries resulting in coldness and numbness in the hands and feet. Moreover, decreased blood supply to the peripheries may cause bluish discoloration of the hands and feet
- Sexual dysfunction – it occurs both in the males and females. Men usually lack interest in sex. There is decreased libido and erectile dysfunction in men.
- Cough – usually dry cough occurs with this drug. it may cause bronchospasm that can be life threatening
- Hyperlipidemia or dyslipidemia – mainly low density lipoprotein (LDL) levels are disturbed with the use of this drug. LDL levels are usually increased and total cholesterol is also increased
- Loss of hair
- Bruising – easy bruising occurs because the drug makes the walls of the vessels fragile
- Jaundice – there is yellow discoloration of skin and sclera in some individuals using Metoprolol
- Fever – Metoprolol can cause persistent fever usually accompanied with sore throat
- Contraindicated in diabetics – Metoprolol must be avoided in diabetics because it alters the blood levels of sugar. Moreover, it masks the symptoms of hypoglycemia such as rapid pulse rate and sweating which can be life threatening
Metoprolol side effects on children
Before prescribing Metoprolol to the child the following conditions must be ruled out because Metoprolol can either cause or aggravate them:
- Known allergy to any beta blocking agent specifically Metoprolol
- Bradycardia or decreased heart rate
- Psychiatric disorders like depression
- Childhood asthma
- Chronic heart failure
- Hepatic disorder
Metoprolol side effects on men
The most common and bothering side effect in men is decreased libido and impotence. Long term use of this drug may lead to sexual or erectile dysfunction leading to impotence. So, while prescribing this drug patient must be made aware of this effect clearly.
Metoprolol side effects on women
Women also have sexual dysfunction while using Metoprolol. There is decreased libido and they lack interest in having sex. Moreover, loss of hair is very prominent in women on Metoprolol.
Metoprolol side effects on pregnant women
Metoprolol is comparatively safe to be used during pregnancy. But it should always be used after proper consultation with your healthcare provider. It has been classified as Category C drug by the US Food and Drug Administration (FDA). This category shows that animal studies have shown adverse effects of the drug on fetal growth and development, however, no controlled human trials have been done so far. One of the studies in humans has shown that Metoprolol has caused perinatal mortality in almost two percent of the cases. More ever, after birth the newborn must be monitored for decreased heart rate and blood pressure for two odd days if the mother was on Metoprolol during pregnancy.
Metoprolol can be used safely by mothers who are breast feeding because very minute quantity of the drug is carried in the milk to the child.
Metoprolol side effects on elderly
In elderly Metoprolol can worsen the signs and symptoms of heart failure occasionally. Patients may have breathlessness, edema all over the body, irregular heart rate, discomfort in chest and wheeze.