Merck’s Cordaptive, an extended-release niacin combined with a flushing inhibitor, has been filed for approval with the FDA, the firm said.

Cordaptive could represent Merck’s latest entrée into the $18-billion market for cholesterol drugs. Its statin Zocor (simvastatin) went off patent last year, but another cholesterol-lowering drug Vytorin, which Merck co-markets with Schering-Plough, has sold well.

Drugs that raise HDL, or “good,” cholesterol are considered a new direction for treatment. Flushing is the only known side effect of niacin, and analysts believe a more tolerable form could be a significant advance.

Back in March, Lehman Bros. analyst Tony Butler told MM&M that Cordaptive, then known as MK-524A, could earn between $800 million and $1 billion “or substantially more, if the clinical outcomes suggests a mortality benefit.”

Merck expects to present Phase III data at next month’s European Society of Cardiology meeting and in November at a gathering of the American Heart Association.

The drug is designed to be used alone or in combination with a statin. MK-524B, Merck’s combination of Cordaptive plus simvastatin (Zocor), is in Phase III trials.

An FDA decision for Cordaptive is anticipated in the second quarter of 2008, Merck said in a statement yesterday. It also plans to file for approval outside the US.

Niaspan, a branded, extended-release form of niacin sold by Kos, had US sales of $473.8 million last year, a 24% increase over 2005. Kos was bought by Abbott Labs in 2006.