September 6, 2023

Find out if propranolol can be used as a substitute for metoprolol, including information on their similarities, differences, and potential side effects. Learn more about these beta-blockers and their uses in managing various conditions.

Can propranolol be substituted for metropolol?

When it comes to treating cardiovascular conditions, beta blockers are often the go-to medications for many healthcare professionals. Two commonly prescribed beta blockers are propranolol and metoprolol. Both drugs are effective in managing high blood pressure, angina, and certain heart rhythm disorders. However, there may be instances where one drug needs to be substituted for the other.

In this comprehensive comparison, we will delve into the similarities and differences between propranolol and metoprolol. We will explore their mechanisms of action, pharmacokinetics, indications, and adverse effects. By understanding the nuances of each drug, healthcare providers can make informed decisions when substituting one for the other.

Propranolol and metoprolol belong to the same class of medications known as beta blockers, but they have distinct characteristics. Propranolol is a non-selective beta blocker, meaning it blocks both beta-1 and beta-2 receptors. On the other hand, metoprolol is a selective beta-1 blocker, primarily targeting beta-1 receptors in the heart. This selectivity may result in differences in their clinical effects and side effect profiles.

It is important to note that before substituting one beta blocker for another, a thorough evaluation of the patient’s medical history, current condition, and response to therapy should be conducted. In some cases, a switch between propranolol and metoprolol may be appropriate, while in others, it may not be advisable. The decision to substitute one drug for another should always be made in consultation with a healthcare professional.

Key differences between propranolol and metoprolol

1. Mechanism of action:

Propranolol belongs to the class of non-selective beta blockers, which block both beta-1 and beta-2 adrenergic receptors. Metoprolol, on the other hand, is a selective beta-1 adrenergic receptor blocker.

2. Indications:

Propranolol is used to treat a wide range of conditions, including hypertension, angina, arrhythmias, and migraine. Metoprolol is primarily indicated for hypertension, angina, and heart failure.

3. Pharmacokinetics:

Propranolol has a shorter half-life compared to metoprolol, which means it needs to be taken more frequently throughout the day. Metoprolol, on the other hand, has a longer half-life, allowing for less frequent dosing.

4. Lipid solubility:

Propranolol is highly lipid-soluble, which allows it to penetrate the blood-brain barrier more easily. Metoprolol, being less lipid-soluble, has limited CNS penetration.

5. Side effects:

Both propranolol and metoprolol can cause common side effects such as fatigue, dizziness, and gastrointestinal disturbances. However, propranolol is more likely to cause bronchospasm and worsening of asthma symptoms due to its non-selective beta-blocking effects.

6. Drug interactions:

Propranolol is known to interact with a wider range of medications compared to metoprolol. It can interact with certain antiarrhythmics, antihypertensives, and antidepressants. Metoprolol has a more limited drug interaction profile.

7. Special populations:

Propranolol is contraindicated in patients with asthma, as it can worsen bronchospasm. Metoprolol, being selective for beta-1 receptors, is generally considered safer for use in asthmatic patients.

8. Cost:

Propranolol is available as a generic medication and tends to be more affordable compared to metoprolol, which is available as a brand-name and generic medication.

Overall, both propranolol and metoprolol are effective beta blockers, but their differences in mechanism of action, indications, pharmacokinetics, side effects, drug interactions, contraindications, and cost should be taken into consideration when choosing between the two for a specific patient.

Mechanism of action

Propranolol and metoprolol are both beta-adrenergic blocking agents, commonly known as beta blockers. They exert their pharmacological effects by blocking the beta-adrenergic receptors in the body.

Propranolol is a non-selective beta blocker, meaning it blocks both beta-1 and beta-2 receptors. By blocking these receptors, propranolol reduces the effects of adrenaline and noradrenaline, leading to a decrease in heart rate, blood pressure, and cardiac output. It also inhibits the release of renin, thereby reducing the production of angiotensin II and aldosterone.

Metoprolol, on the other hand, is a selective beta-1 blocker, which means it primarily blocks the beta-1 receptors found in the heart. By selectively blocking these receptors, metoprolol reduces the heart rate and cardiac output, without significantly affecting the beta-2 receptors in the lungs and blood vessels.

Both propranolol and metoprolol also have membrane-stabilizing properties, which contribute to their antiarrhythmic effects. These properties allow them to stabilize the cell membrane and reduce the automaticity of cardiac cells.

Additional Effects


In addition to blocking beta receptors, propranolol has been found to have other pharmacological effects. It has been shown to inhibit the release of neurotransmitters such as dopamine and serotonin, and it also has anti-inflammatory properties. These additional effects may contribute to its efficacy in treating conditions such as anxiety, migraine, and essential tremor.

Metoprolol, on the other hand, primarily acts as a beta blocker and does not have significant effects on other neurotransmitters or inflammation.


Pharmacokinetics refers to the study of how drugs are absorbed, distributed, metabolized, and eliminated by the body. Understanding the pharmacokinetics of a drug is essential for determining its efficacy and safety.


Both propranolol and metoprolol are well absorbed after oral administration. However, propranolol has a higher bioavailability compared to metoprolol, meaning that a larger proportion of the administered dose reaches the systemic circulation.

Propranolol is rapidly absorbed, with peak plasma concentrations occurring within 1 to 2 hours after oral administration. It undergoes extensive first-pass metabolism in the liver, resulting in a lower systemic bioavailability. The absorption of propranolol can be affected by food, with higher peak plasma concentrations observed when taken on an empty stomach.

Metoprolol is also rapidly absorbed, with peak plasma concentrations occurring within 1 to 2 hours after oral administration. It undergoes significant first-pass metabolism in the liver as well, resulting in a lower systemic bioavailability. However, the absorption of metoprolol is not significantly affected by food.


Both propranolol and metoprolol have a high volume of distribution, indicating that they distribute widely throughout the body. They are extensively bound to plasma proteins, with propranolol being approximately 90% bound and metoprolol being approximately 5% bound.

Propranolol has a higher lipophilicity compared to metoprolol, which may contribute to its higher tissue distribution. It is able to cross the blood-brain barrier, allowing it to exert its effects in the central nervous system.

Metabolism and Elimination

Propranolol is extensively metabolized in the liver by the enzyme CYP2D6. It undergoes both oxidative and conjugative metabolism, resulting in the formation of several metabolites. These metabolites are primarily excreted in the urine, with a small portion excreted in the feces.

Metoprolol is also metabolized in the liver, primarily by the enzyme CYP2D6. It undergoes oxidative metabolism, resulting in the formation of several metabolites. These metabolites are primarily excreted in the urine.

The elimination half-life of propranolol is approximately 3 to 6 hours, while the elimination half-life of metoprolol is approximately 3 to 7 hours. Both drugs are primarily eliminated through hepatic metabolism.

It is important to note that both propranolol and metoprolol can be affected by genetic polymorphisms in the enzymes involved in their metabolism, which may lead to interindividual variability in drug response and pharmacokinetics.


Both propranolol and metoprolol are commonly used beta-blockers that are indicated for various cardiovascular conditions.

Propranolol is primarily indicated for:

  • Hypertension (high blood pressure)
  • Angina (chest pain)
  • Arrhythmias (irregular heart rhythms)
  • Migraine prophylaxis (prevention of migraines)
  • Essential tremor (uncontrollable shaking)
  • Performance anxiety
  • Post-traumatic stress disorder (PTSD)
  • Hyperthyroidism (overactive thyroid)

Metoprolol is indicated for:

  • Hypertension (high blood pressure)
  • Angina (chest pain)
  • Heart failure
  • Myocardial infarction (heart attack)
  • Arrhythmias (irregular heart rhythms)

It is important to note that while propranolol and metoprolol have some overlapping indications, they may differ in their specific uses and dosages depending on the individual patient’s condition and response to treatment. Therefore, it is crucial to consult with a healthcare professional for appropriate prescribing and dosage recommendations.

Side effects

Both propranolol and metoprolol can cause side effects, although the specific side effects may vary between individuals. It is important to note that not everyone will experience these side effects, and some individuals may experience different side effects than others.

Common side effects

  • Dizziness
  • Fatigue
  • Nausea
  • Vomiting
  • Diarrhea
  • Headache
  • Insomnia
  • Cold hands or feet

Less common side effects

  • Depression
  • Confusion
  • Nervousness
  • Slow heart rate
  • Low blood pressure
  • Shortness of breath
  • Unusual weight gain
  • Swelling of the hands, feet, or ankles

If you experience any severe or persistent side effects while taking propranolol or metoprolol, it is important to contact your healthcare provider immediately. They can provide guidance and determine if any adjustments to your medication are necessary.

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