The drugmaker scrambles to boost Lipitor by signing a deal to have its cholesterol pill placed on the Express Scripts preferred formulary as of Friday. This is a big deal, of course, because Express Scripts is a big pharmacy benefits manager, and Lipitor hasn’t been on its formulary since 2005.

For Pfizer, this couldn’t have happened a moment too soon. Lipitor currently has 34.3 percent of the market for new scrips written, and a 36.3 percent share of all scrips, according to research note issued this morning by Barbara Ryan of Deutsche Bank. However, she points out that Lipitor’s total scrips are down 9.4 percent so far this year, reflecting last June’s introduction of generic Zocor.

What Pfizer had to give up isn’t clear. Terms of the deal weren’t disclosed, although Celebrex and the Xalatan glaucoma drug are also on the formulary. A joint statement says that “the majority of all discounts and related revenue under the program goes to Express Scripts’ clients, with specific amounts determined by individual client contracts.”