For the last year, Pfizer has been laying the groundwork to combat the looming competition against Lipitor, forging deals with insurers, pharmacy benefit managers and patients to meet or beat the price of its generic replacements.

As it loses its patent for Lipitor, the top-selling cholesterol drug, on Wednesday, Pfizer is completing relationships and shoring up discounts — like a reduced co-payment of $4 a month versus the $10 customers would pay for many generic prescriptions.

Some deals require pharmacies to reject prescriptions for low-cost generics, starting Thursday, and substitute a discounted name-brand Lipitor. Some deals have blocked generic makers from mail-order services that account for an estimated 40 percent of all Lipitor prescriptions.

The company’s aggressive strategy may offer lessons for drug makers facing similar losses of patent protection for other blockbuster drugs over the next few years, and may chart a new path for shifts between the big pharmaceutical companies and generic rivals.

Lipitor was the first drug to exceed $10 billion a year in sales, and accounted for almost one-quarter of Pfizer’s revenue in the last decade.

With Pfizer’s plans to try to maintain brand loyalty for the next six months becoming public, industry analysts have raised the company’s earnings outlook by 2 to 4 percent, and now estimate that it could retain 40 percent of the market through next year. Pfizer officials declined to comment on that estimate.

Aiding its chances is a stumbling start-up by generic competitors. Ranbaxy Laboratories, the Indian subsidiary of the Japanese drug company Daiichi Sankyo, won the right to bring the first generic version to market. But Ranbaxy has disclosed it is under federal investigation. It has not yet received Food and Drug Administration approval. Ranbaxy’s president has said it will be ready by Thursday.

Watson Pharmaceuticals of Parsippany, N.J., is a second competitor with a generic version of the drug authorized and manufactured by Pfizer. But Watson has to give about 70 percent of its profits to Pfizer, according to the investment house Sanford C. Bernstein & Company. And Pfizer’s own deals are undercutting both Watson and Ranbaxy on price.

“Pfizer’s tactic of dressing up as a generics company is pulling the rug under the incentive system created to foster the development of generic drugs,” David A. Balto, a lawyer for some generic makers and a former policy director for the Federal Trade Commission, said Tuesday.

Pfizer’s strategy so far is limited to the first 180 days after Lipitor goes off patent. During that period, under law, generic competition is limited and the first entries have historically charged fairly high prices to recoup their costs. After the first six months, any company can enter the generic market, and prices plunge.

Although Ranbaxy and Watson have not yet announced their prices, one top Pfizer official said on Tuesday that its new discounts could be adjusted to beat any tit-for-tat reduction in the expected generic pricing.

“They are a set contract but they could change,” said David S. Simmons, president and general manager of Pfizer’s established products unit. “I mean, it’s at the discretion of two parties. They could change.”

Mr. Simmons said the intention of Pfizer’s discount was to keep Lipitor “at or below generics’ cost to the health care system.”

The discount is also extending to many Medicare prescription drug plans that will dispense Lipitor even if patients ask for generics, according to a memo released by an advocacy group called Pharmacists United for Truth and Transparency.

The memo, from CVS/Caremark, a pharmacy benefit management company, and dated Monday, notified pharmacies that the generic form of Lipitor would not be covered for 29 prescription drug plans it managed for Medicare Part D. Instead, any prescription claims for generic atorvastatin will be rejected with a notice saying: “Brand Lipitor will pay at generic co-pay.”

The company’s memo did not disclose the financial terms.

The government may receive the rebates that drug manufacturers pay to benefit managers and insurers if they are fully disclosed and characterized as rebates, not fees, according to a March report by the Office of the Inspector General for the Department of Health and Human Services. But benefit managers’ records may not be accessible or auditable, it added.

Express Scripts, another large pharmacy benefit manager, is recommending that its clients not accept Pfizer’s deals under the reasoning that it could cost more in the long run, according to F. Everett Neville, vice president for pharmaceutical strategy. “They’re 180-day deals but no one knows what the price of the generic may be if they lower their prices in a month or two,” he said.

Medco Health Solutions, another giant benefit manager, is also recommending that customers switch to the generic version of Lipitor. Medco is sending faxes to tens of thousands of physicians and letters to some of the million people who buy Lipitor through the company, saying they should use generic atorvastatin to save money, said Timothy C. Wentworth, Medco’s group president for employer and key accounts.

At the same time, both Express Scripts and Medco say their own mail-order services will use Lipitor as a “house generic” because Pfizer has guaranteed to match the price and assured a supply.

With mail order increasingly dominant — accounting for an estimated 30 percent of Lipitor sales — those deals are important. Timothy Anderson of Bernstein Research estimated that Pfizer would maintain 90 percent of the mail order market.

Aetna is not taking Pfizer’s offer. “We decided not to participate in the rebate program because it doesn’t support our generic-first philosophy,” an Aetna spokesman, Matt Wiggin, said.

Kevin Hooks, managing partner of the Virtuous Group, a benefits consultant in Las Vegas, also said: “We don’t know what the generic is going to be priced yet. He added, “Right now we think it’ll be a better deal for members to get Lipitor for the first six months, with discount, and then kill the deals.”

Consumers will certainly benefit from generic prices. And Pfizer is making sure of that with a program called Lipitor for You, offering the $4 co-payment card and direct delivery of Lipitor. The program is limited to privately insured people, though, because government programs like Medicare say such discounts could violate antikickback laws and lead to higher health spending.

It’s unclear how taxpayers will fare through the Medicare Part D drug benefits program, administered by private companies. Tony Salters, a spokesman for Medicare, said he could not comment.

Christine K. Cramer, a spokeswoman for CVS/Caremark, said its drug plans had already included the Lipitor rebates in its 2012 Medicare bids, thus lowering premiums for the government and Lipitor users.

Even at the lower price, Pfizer has a huge margin because of the relatively low cost of materials for Lipitor, Bernstein Research estimated. Pfizer, the benefit managers and some insurers insist all of the new discount will be passed along to consumers, companies and other payers.

“Who knows who it’s good for?” said Dr. John Santa, director of health ratings for the independent nonprofit Consumer Reports. With all the companies involved, “and they say consumers are going to be good here, I’d be skeptical,” he added.

Adam J. Fein, a pharmaceutical consultant and blogger, said: “It’s kind of a forerunner of what’s going to happen over the next two years as everyone battles for the incremental profit in the generic wave.” He added: “You have over $80 billion in drugs that are going to go generic. Say $80 billion settles to $10 billion eventually. That’s $70 billion savings. But during that period going from 80 to 10 there’s going to be a lot of money made by the various channel intermediaries, and they all want a piece of that pie.”