NEW YORK (CNN/MONEY) - Bristol-Myers Squibb stock sank to its lowest level in more than four years Tuesday as investors prepared for the drug maker to cut its earnings guidance, but how big the redution will be remains to be seen.

Bristol-Myers (BMY: down $2.16 to $38.24, Research, Estimates) could be set to cut as much as 20 cents a share off its previous 2002 guidance of $2.25 to $2.35 a share, according to industry analysts, down from the $2.41 a share earned in 2001.

In its annual report filed with the Securities and Exchange Commission Monday, the maker of the cholesterol drug Pravachol and the pain killer Excedrin said it sold too much to wholesalers last year, which will put a dent in this year's sales.

Bristol-Myers said wholesalers now have about four weeks' worth of additional drugs in inventory, and that it was "developing a plan to reduce wholesaler inventory levels," a reduction that "will negatively impact its financial results in future periods."

Analysts said they are reading that as a cue for the company to cut its guidance, probably before it announces first-quarter earnings on April 25.

Mark Striker, drug analyst with Salomon Smith Barney, said in a research note he estimates four weeks of additional inventory equals about earnings of 20 cents a share, but the key question is "how much stocking did [Bristol-Myers'] 2002 EPS guidance include?"

Trevor Polischuk, analyst with Lehman Bros., said there are "a few too many unknown variables" but is estimating a 10 to 14 cent reduction in earnings which his firm still officially has at $2.29 a share.

"There are some that see (the reduction) as high as 20, but we think there will be some mitigating factors that will soften the bottom line," Polischuk said.

He added it is also unclear whether the company would include the reduction in one quarter or spread it out over the entire calendar year.

Tim Anderson, analysts with Prudential Securities, said Bristol-Myers could try and pass off the wholesale inventory reduction as a one-time charge, but doubted that would happen. Anderson is looking for a drop of 10 to 15 cents.

Shares of Bristol-Myers Squibb fell more 5 percent as investors digested the news.

Anderson said it is unlikely the stock would see a further drop from the inventory problem.

"I think it's kind of factored into the price at this point," he said. "It creates uncertainty in the numbers and that keeps the stock in check, in that nobody will want to buy Bristol ahead of a possible cut."

The revelation about wholesales industries follows disappointing news about Bristol-Myers' heart medication Vanlev as well as its joint venture with ImClone Therapeutics (IMCL: down $0.15 to $24.90, Research, Estimates) to develop and market cancer drug Erbitux.

Polischuk said problems with excess wholesale inventories normally rectify themselves in the next quarter and there is a lot of speculation as to why that didn't happen this time with Bristol-Myers.

He noted at the end of last year the company was under a lot of pressure to produce good numbers as well as facing uncertainty about patent expiration for its blockbuster diabetes drug Glucophage.

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Generic versions of Glucophage arrived at the end of January and Polischuk said wholesalers may have been left with a glut of the brand-name drug. But he said the company is in a difficult position about revealing more information since it already knows its first-quarter number and may be concerned about fair disclosure rules.