Norepinephrine stimulates the nerves that control the muscles of the heart by binding to the β1- and β2-adrenergic receptors. Carvedilol blocks the binding to those receptors, which both slows the heart rhythm and reduces the force of the heart's pumping. This lowers blood pressure thus reducing the workload of the heart, which is particularly beneficial in heart failure patients.
Norepinephrine also binds to the α1-adrenergic receptors on blood vessels, causing them to constrict and raise blood pressure. Carvedilol blocks this binding to the α1-adrenergic receptors too, which also lowers blood pressure.
Relative to other beta blockers, carvedilol has minimal inverse agonist activity. This suggests that carvedilol has a reduced negative chronotropic and inotropic effect compared to other beta blockers, which may decrease its potential to worsen symptoms of heart failure. However, to date this theoretical benefit has not been established in clinical trials, and the current version of the ACC/AHA guidelines on congestive heart failure management does not give preference to carvedilol over other beta-blockers.
Carvedilol is indicated in the management of congestive heart failure (CHF), as an adjunct to conventional treatments (ACE inhibitors and diuretics). The use of carvedilol has been shown to provide additional morbidity and mortality benefits in severe CHF. Carvedilol (Carvil) is available at the following doses 3.125 mg (smallest), followed by 6.25 mg,12.5 mg, and 25 mg white tablets. Coreg CR is available at the following doses: 10mg(white/green capsules), 20mg(white/yellow capsules), 40mg(yellow/green capsules), and 80mg(white capsules). 
U.S. supply issues
On January 10, 2006 carvedilol supply became limited in the United States, due to changes in documentation procedures at a plant. This was lifted on April 27, 2006 in a Dear Pharmacist letter.
Approval of controlled-release formulation
On October 20, 2006, the FDA approved a controlled release formulation of carvedilol; it is marketed as Coreg CR.
11. Subhashis Chakraborty, Dali Shukla, Brahmeshwar Mishra & Sanjay Singh.Clinical updates on carvedilol: a first choice beta-blocker in the treatment of cardiovascular diseases. Expert Opin Drug Metab Toxicol. 2010 Feb;6(2):237-50. DOI 10.1517/17425250903540220, PMID 20073998