Laremy asked
I heard carvedilol 25mg is not equivalent to metoprolol 25mg? If you take carvedilol 25mg its like taking 100 mg metoprolol Just wanted to know if this is true. Thank you!
Answer
You are correct in saying that 25mg of carvedilol is not equivalent to 25mg of metoprolol. Rarely is it the case where you can simply convert one drug to another on a milligram per milligram basis, even when they are similar or in the same class of medications. Some drug classes, like opioids, do have conversions between one another based on their analgesic activity but this is certainly not the case for beta blocker medications.
Carvedilol and metoprolol, although both considered "beta-blockers" actually have quite a different mechanism of action. There are multiple 'beta' receptors in the body, with a wide range of effects when activated or antagonized. The 'Beta-1' receptor is mostly expressed in the cardiac tissue. Metoprolol is known as a 'beta-1 selective (cardioselective)" medication. Many beta blockers work on both beta-1 and beta-2, which can have significant effects on the body in addition to the effects on blood pressure, pulse rate etc...
Carvedilol is known as a combined alpha- and nonselective beta-blocker. It actually works on many different receptors in the body and has a much broader range of action when compared to metoprolol. It is non-selective, meaning it works on more than just the 'beta-1' receptor and also work on alpha receptors which has vasodilatory effects.
Couple the information above, with the fact that different drug compounds just have different potencies, then you can see that why there is no accepted conversion ratio between carvedilol and metoprolol.
Aside from the different mechanism of action of both drugs, they are different in terms of their potency as well.
Carvedilol (brand name Coreg) is supplied in 3.125mg, 6.25mg, 12.5mg and 25mg immediate release tablets. Depending on what the carvedilol is being used for, the dose given may vary. For example, if heart failure is the issue, a physician may start the dose of carvedilol at 3.125mg twice a day and increase from there based on response. High blood pressure may yield a carvedilol dose of 6.25mg twice a day to start, and then possibly titrated up to 25mg twice a day.
Metoprolol (brand name Lopressor) is available in 25mg, 37.5mg, 50mg, 75mg, and 100mg immediate release tablets. Metoprolol is frequently used in angina sufferers (chest pain) at a starting dose of 50mg twice daily. Metoprolol is also used after a myocardial infarction (heart attack), dosed at 100mg twice a day to prevent another episode.
Carvedilol is more commonly used in heart failure or high blood pressure (hypertension) whereas metoprolol is used in angina and/or after a heart attack. As you can see by the available strengths of each drug listed, 25mg is the highest available strength of carvedilol vs. the lowest that the metoprolol comes in.
When switching from one beta blocker to another, the physician may choose to cautiously back off on the dose to monitor the effects of a new medication. Always consult your doctor before switching from one prescription medication to another.
