By Laura Mandaro

SAN FRANCISCO (Dow Jones) -- After a long dry spell, the stock market once again is about to drink from the well of initial public offerings, with a $680 million debut from the maker of Enfamil infant-formula headlining four deals on tap this week.

In keeping with the skittish tone of stocks, the largest and oldest name among the crop is generating the most buzz, as Mead Johnson Nutrition Co., a spin-off of Bristol-Myers Squibb Co. (BMY), priced its offering Tuesday evening at $24 a share, and is expected to begin trading on Wednesday.

"Institutions that do the bulk of the IPO deals and receive allocations are interested in high- quality companies that have excellent financials and experienced management," said Scott Sweet, principal researcher at advisory firm IPOBoutique.com in Tampa, Fla.

"They are reluctant to do start-up IPOs," he said.

Mead Johnson said in a statement that it increased its IPO to 30 million shares from an initial size of 25 million. The shares are expected to begin trading Wednesday on the New York Stock Exchange, under the ticker symbol "MJN."

Mead Johnson said it expects to use the roughly $680 million in proceeds to "repay intercompany obligations."

Citi (C), Morgan Stanley (MS), Banc of America Securities LLC (BAC), Credit Suisse (CS) and J.P. Morgan (JPM) are acting as joint book-running managers for the IPO, Mead Johnson said.

Mead Johnson will be the first initial U.S. stock offering since November, when Grand Canyon Education (LOPE) broke the last drought with a $144.5 million offering, according to Dealogic.

It will also rank as the largest U.S. market debut since April, when American Water Works (AWK) came out for $1.4 billion.

Bristol-Myers Squibb is expected to retain a majority stake in the Evansville, Ind., company, which has been selling baby formula and other nutritional products since 1905. It recorded $2.6 billion in sales last year and competes with Abbott Laboratories' (ABT) Similac brand.

"The numbers plus its association with Bristol Myers make it a fairly easy sale," said IPOBoutique's Sweet, who had predicted that heavy demand for shares would prompt underwriters to expand the size of the deal.

The four deals coming to market this week are expected to raise more than $940 million in combined new capital even as the major stock indexes remain mired in bear territory. But the offerings highlight the fact that some companies, particularly more mature names, are starting to test investors' appetite to turn their cash hoards into new debt and stocks.

"The ones that are sitting in the pipeline tend to be a bit larger companies on average," said Jackie Kelley, America's IPO leader for Ernst & Young. "That's what we're thinking leads us to a stronger IPO market."

The week's other initial offerings include Madison Square Capital Inc., a newly established real estate investment trust that plans to raise an estimated $200 million; vehicle-armor maker O'Gara Group, with a $144 million deal; and renewable energy firm Changing World Technologies Inc., which hopes to raise about $36 million.

Since the Grand Canyon offering, plenty of companies have aspired to tap the stock market for capital. But with the major indexes headed south, many pulled those plans or let them languish.

The number of companies remaining in the IPO pipeline dropped to 57 by year-end, or a 30% decrease from the end of the third quarter, according to Ernst & Young. But the average deal size rose to $272.7 million in the fourth quarter from $231.4 million in the third quarter.

The tough climate hasn't prevented start-ups, the traditional candidates for initial public offerings, from attempting offerings.

In a sign some entrepreneurs see riches rising from the ashes of the U.S. financial system, Madison Square Capital, whose offering is expected to price Wednesday, intends to invest on a leveraged basis in mortgage-backed securities guaranteed by a U.S. government agency or issued by Fannie Mae or Freddie Mac.

The gap between these securities' yields and Treasurys has fallen in the past month as the Federal Reserve has bought this debt to drive down interest rates. But these spreads are still three times as high as they were at the start of the credit crunch.

"We believe that the current market disruptions in the U.S. housing industry, residential mortgage sector and overall credit markets have created an exceptional opportunity for us to implement our business plan as a new company," said the company in an SEC filing.

Online restaurant reservation service OpenTable in late January filed plans to offer $40 million in new shares to the public.

But market volatility has caused some companies to withdraw or pare their capital raising plans.

Late last week, independent oil refiner Big West Oil Partners, L.P canceled its IPO plans, citing current market conditions. Traditional energy companies are reeling as oil prices sink below $40 a barrel.

O'Gara, which is expected to go public Wednesday, has cut the price on the shares it plans to sell to a range of $15 to $16 a share from $17 to $19 previously, according to IPOBoutique.com.