Three U.S. senators are raising questions with Pfizer (NYSE: PFE) over its deal making for its megablockbuster cholesterol drug Lipitor as generic drug makers step up to market the drug, most recently Ranbaxy Laboratories, an India-based generic drug developer.

Max Baucus (D-Montana), Chuck Grassley (R-Iowa) and Herb Kohl (D-Wisconsin) are concerned that Pfizer's deals with pharmacy benefit managers will undermine the sale of generic versions of Lipitor. Their letters request that the company, benefit managers and insurance companies provide copies of the Lipitor agreements, documents and communications pertaining to the agreements and presentations describing the agreements no later than Dec. 21, according to Seeking Alpha.

Baucus said it wanted to protect taxpayer dollars and access to medicines.

Among Pfizer's efforts are offering patients $4 co-pay cards for Lipitor at a local participating pharmacy or direct delivery of their prescription, an effort it is promoting through physician practices, advertising and through the website,

Lipitor had sales of more than $10 billion last year.

Last month, the company told reporters in New York that one-third of people taking Lipitor want to continue taking the branded drug, so it was working with drugstores and mail-order providers to provide discounts on Lipitor. Medco Health Solutions, for example, a pharmacy benefit manager, is supplying Lipitor for 180 days through its direct mail service, according to The Wall Street Journal. In Pennsylvania and New Jersey, where laws instruct pharmacies to use cheaper generic drugs when available, physicians will have to specify that their patients get Lipitor if they are to receive the branded drug.

Ranbaxy gained approval to make atorvastatin calcium tablets in doses running from 10 milligrams to 80 milligrams. The drug will be manufactured by Ohm Laboratories in New Brunswick, New Jersey, according to a statement from the U.S. Food and Drug Administration.

Additionally, Ranbaxy has an agreement with Teva Pharmaceuticals' U.S. arm for a portion of the profits from sales of atorvastatin during Ranbaxy's 180-day, first-to-file exclusivity period, but the terms were not disclosed.

Watson Pharmaceuticals (NYSE: WPI), the Parsippany, New Jersey manufacturer, secured the authorized generic version of Lipitor. In a supply and distribution agreement with Pfizer, the New York pharmaceutical company manufactures and supplies Watson with all dosage strengths of the authorized generic product.

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