What is carvedilol? How does it work (mechanism of action)?
Carvedilol is used for treating high blood pressure and congestive heart failure. It is related to labetalol (Normodyne, Trandate). Carvedilol blocks receptors of the adrenergic nervous system, the system of nerves in which adrenalin (epinephrine) is active. Nerves from the adrenergic system enter the heart and release an adrenergic chemical (norepinephrine) that attaches to receptors on the heart's muscle and stimulates the muscle to beat more rapidly and forcefully. By blocking the receptors, carvedilol reduces the heart's rate and force of contraction and thereby reduces the work of the heart. Carvedilol also blocks adrenergic receptors on arteries and causes the arteries to relax and the blood pressure to fall. The drop in blood pressure further reduces the work of the heart since it is easier to pump blood against a lower pressure.
The FDA first approved carvedilol in 1995.
What are the uses for carvedilol?
- Carvedilol is a diuretic or "water pill" used to control high blood pressure (hypertension). In addition to treating high blood pressure, carvedolil is prescribed to treat:
- Carvedilol may be used in combination with other drugs to manage mild or moderate congestive heart failure. When it is combined with other treatments for heart disease among patients with recent heart attacks, carvedilol can reduce the risk of a second heart attack by 40% and increase survival among patients with congestive heart failure.
- Carvedilol is also used for treating angina (chest pain from heart disease).
What are the side effects of carvedilol?
The most common side effects of carvedilol are:
- Dizziness
- Edema (fluid accumulation)
- Decreased heart rate
- Low blood pressure
- Weight gain
- increased blood glucose levels (hyperglycemia)
- Diarrhea
Postural hypotension (a rapid decrease in blood pressure when going from the seated to the standing position that causes lightheadedness and/or fainting). Taking carvedilol with food minimizes the risk of postural hypotension.
Other common side effects of carvedilol are an irregular heart rhythm and vision abnormalities.
Carvedilol should be used cautiously in patients who use diuretics or who are elderly or that have:
- Cirrhosis
- Asthma
- Peripheral vascular disease
- Hyperthyroidism
- Prinzmetal's variant angina (angina at rest)
- Kidney disease.
What is the dosage for carvedilol?
- Carvedilol tablets are usually given twice daily. For high blood pressure, the dose is 6.25 mg twice daily to a maximum of 25 mg twice daily.
- For congestive heart failure, the dose is 3.25 mg twice daily to a maximum of 25 mg twice daily. A maximum dose of 50 mg twice daily has been used in persons weighing more than 85 kg (187 pounds).
- Carvedilol should be taken with food to slow its absorption and reduce the occurrence of low blood pressure when rising from a sitting or sleeping position (orthostatic hypotension). Stopping and changing doses of carvedilol should be done under the direction of a doctor because sudden changes in dose can result in serious cardiac complications such as arrhythmias.
- The dose range for treating heart failure or high blood pressure with extended-release capsules is 10 to 80 mg once daily.
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Which drugs or supplements interact with carvedilol?
Carvedilol can mask early warning symptoms of low blood sugar (hypoglycemia) such as tremors and increased heart rate. (These symptoms are caused by activation of the adrenergic nervous system that are blocked by the carvedilol.) Therefore, patients with diabetes taking medications that lower blood sugar such as insulin or oral anti-diabetic medications may need to monitor their blood sugar more often.
Carvedilol taken with calcium channel blockers (CCBs) such as diltiazem (Cardizem) or verapamil (Calan) may trigger an irregular heart rhythm or an increase in blood pressure.
Reserpine, monoamine oxidase inhibitors (phenelzine or isocarboxazid) and clonidine (Catapres), because they have similar mechanisms of action as carvedilol, may greatly accentuate the effects of carvedilol and cause a steep decline in blood pressure and/or heart rate. Close monitoring of blood pressure and heart rate may be needed.
Carvedilol may cause an increase in digoxin (Lanoxin) blood levels. Therefore, in patients receiving digoxin, the digoxin blood level should be monitored if carvedilol is started, adjusted, or discontinued.
Rifampin (Rifadin) can sharply decrease the carvedilol blood level. Therefore, in patients taking rifampin, the dose of carvedilol may need to be increased.
Carvedilol shares a common pathway for elimination by the liver with several other drugs such as quinidine (Quinaglute), fluoxetine (Prozac), paroxetine (Paxil), or propafenone (Rythmol). Use of these drugs may block the elimination of carvedilol. No studies have been done to confirm these effects on the elimination of carvedilol; however, carvedilol blood levels may be increased (along with the risk for carvedilol's side effects) if patients are taking any of these drugs.
Carvedilol may increase cyclosporin (Sandimmune, Neoral) blood levels. The dose of cyclosporin may need to be adjusted when the two drugs are used together.
Amiodarone (Cordarone) may increase carvedilol levels in the blood, increasing the effects and potential for toxicity of carvedilol.
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Is carvedilol safe to take if I’m pregnant or breastfeeding?
- Safe use of carvedilol during pregnancy has not been established.
- No studies with carvedilol are available in nursing mothers; however, use is not recommended due to the risk of a slow heart rate in the infant.
What else should I know about carvedilol?
Carvedilol:
- Is available in generic form.
- Needs a prescription from your doctor.
- Is available as:
- Tablets of 3.125, 6.25, 12.5, and 25 mg.
- Capsules (Extended Release) of 10, 20, 40, 80 mg
- Tablets should be stored at room temperature, 15 C and 30 C (59 F and 86 F).
Brand names available for carvedilol in the US are Coreg and Coreg CR (extended release).