The news of the Food and Drug Administration's approval of a new heart failure drug by Novartis was met this week with unusually strong enthusiasm from the medical community. Many talked of the drug as a sure-fire "blockbuster" and "breakthrough" that will help millions. Clyde Yancy, a cardiologist, told MedPage Today, "YEAH!" Yancy, chief of the division of cardiology at Northwestern University Feinberg School of Medicine, said he had already received e-mails from patients requesting access to the drug.

Below we answer some frequently asked questions about the new medication.

Why is this such a big deal?

About 26 million people worldwide suffer from heart failure, a condition in which the heart is weakened and unable to pump enough blood and oxygen to a body's organs. It is usually caused by a heart attack or high blood pressure and tends to worsen over time. In its advanced stages, the available interventions are very invasive, involving open-heart surgery or a pacemaker. Patients are also typically treated with drugs like enalapril, an ACE inhibitor that is the standard of care, or beta blockers, which are also used to control blood pressure.

Entresto -- previously known as LCZ696 -- is the first of a new class of drugs, called angiotensin receptor neprilysin inhibitors, for the condition and is a tablet that is taken twice a day. The results of studies of the drug that were published last year have been viewed by many medical professionals as nothing short of remarkable. In one large trial called PARADIGM that involved 8,442 patients, researchers gave half the patients the Novartis drug and half enalpril. They found those on Entresto had a 20 percent reduction in risk of death or hospitalization.

The results were so promising that the FDA granted it fast-track designation. “This is one of those once-in-a-decade kind of breakthroughs, to get a drug that extends life so substantially,” David Epstein, head of Novartis’s pharmaceutical division, told the New York Times in an interview.

Who is eligible for the drug?

Patients with what's known as class II-IV chronic heart failure, with reduced ejection fraction, will be able to get the drug with a prescription. That includes about 2.2 million of the 5.1 million Americans suffering from heart failure. The company is sponsoring other studies to see whether it could be beneficial to those with other forms of heart failure, as well.

How does it work?

Entresto is made up of two components. The first is valsartan, which is the same active ingredient in the already approved drug Diovan, which is used to treat high blood pressure and congestive heart failure. Valsartan is thought to block the harmful effects of the hormone system that regulates blood pressure and fluid balance. The other ingredient, sacubitril, is believed to enhance the body's protective neurohormonal systems.

What are the potential side effects?
The FDA said the most common side effects noted in clinical trial participants were: low blood pressure (hypotension), high blood potassium levels (hyperkalemia), and poor function of the kidneys (renal impairment). Some people also experienced an allergic reaction called angioedema that usually involves swelling of the lips or face.

How much does it cost?

About $4,500 per year, or $12.50 a day for two tablets a day. (Novartis has said it estimates that annual sales could hit $5 billion.)

Will insurance companies pay for it?

That's the big question of the day. The ACE inhibitors currently used to treat heart failure are generics and incredibly cheap. According to Forbes, "So now a new battle faces Novartis: convincing payers to allow access to this drug for patients in their healthcare systems. Despite the fact that Entresto is a drug that will allow heart failure patients to live longer and avoid hospitalizations, Novartis is now in discussions to justify the price of the drug with respect to the overall benefits to patients and the saving of downstream healthcare costs. In other words, it will be awhile before many heart failure patients will get access to this important medicine."

Correction: An earlier version of this post incorrectly described the function of the two active ingredients in the drug. 

This post has been updated.

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