Teva Pharmaceutical Industries

(TEVA) - Get Report

said Friday that it has received final approval to sell low-price copies of

Merck's

(MRK) - Get Report

big cholesterol drug Zocor.

The clearance by the Food and Drug Administration gives Teva the exclusive right for six months to sell four dosage strengths of Zocor, whose U.S. patent expires today. Zocor has been Merck's best-selling medication, providing $3.14 billion in U.S. revenue and $1.24 billion in foreign sales last year.

Zocor is the second-biggest seller in the statin class of cholesterol fighters behind

Pfizer's

(PFE) - Get Report

Lipitor, and it's been particularly newsworthy this week, not as much for the patent expiration itself as for the plan Merck has formulated to hold on to at least some of its market share.

Merck has signed an unusual deal with

UnitedHealth Group

(UNH) - Get Report

, a managed care company, that will let Zocor users pay less out-of-pocket for the brand-name drug than they would for Teva's generic version. Normally, generic drugs are priced well below the brand-name product they copy.

Another score for Merck came when health-benefits company

WellPoint

(WLP)

said it would offer name-brand Zocor, and not generics, by way of its mail-order pharmacy, according to

The Wall Street Journal

.

The FDA's endorsement of Teva's drug comes after a federal judge denied a last-minute attempt by another company to block it from selling generic Zocor. The Sandoz unit of Swiss drug giant

Novartis

(NVS) - Get Report

sought a temporary restraining to prevent the FDA from approving Teva's application. Sandoz wanted the temporary restraining order until a federal district court in Washington could rule on its request for a preliminary injunction.

The Sandoz matter is related to a legal battle involving Teva and the FDA over the first-to-file law. The law grants six-months marketing exclusivity to a company that submits the first proper application to the FDA to make a low-priced copy once a brand-name drug's patent expires.

This six-month period is crucial amid the cutthroat pricing of generic drugs, and Sandoz complained that Teva wasn't entitled to the marketing advantage. In October, the FDA determined that the six-month rule didn't apply to Teva, but seven weeks ago, a federal judge issued a decision in favor of the company, ruling that the FDA erred.

The judge sent the case back to the FDA, which subsequently appealed the ruling. The appeal hasn't been argued. Several generic companies have received tentative FDA approval to sell generic Zocor once the six-month exclusivity period expires.

India's

Ranbaxy Laboratories

was first-to-file for a generic version of a fifth dosage strength of Zocor. Teva will sell four dosage strengths ranging from 5 milligrams to 40 milligrams, and Ranbaxy will sell 80-milligram generic Zocor.

"We are obviously pleased to receive final approval of our generic version of Zocor," said Israel Makov, president and CEO of Teva, the Israeli company that is the world's largest seller of generic drugs. Sandoz is the second biggest.

"This approval is another example of our agency's efforts to increase access to safe and effective generic alternatives as soon as the law permits," said Gary Buehler, director of FDA's office of generic drugs, in a prepared statement. He didn't mention the agency's legal fight with Teva.

Despite their victories, Teva and Ranbaxy won't enjoy all the benefits of their six-month exclusivity. Merck has a deal with

Dr. Reddy's Laboratories

(RDY) - Get Report

enabling the company, another generic-drug distributor, to sell low-priced versions of Zocor.

Agreements like the one with Dr. Reddy's, a practice known as authorized generics, are reached when the brand-name company licenses its product to a generic company. The idea is for the brand-name company to recoup some sales after its premium-priced drug goes off-patent.