NEW YORK (AP) -- Drugmaker King Pharmaceuticals Inc. said Friday it offered Alpharma Inc. $1.4 billion in cash as part of an unsolicited buyout bid in a move to create a large diverse specialty pharmaceutical company and expand its pain therapy products.

Bristol, Tenn.-based King said it offered $33 per share to Alpharma's board of directors, amounting to a 37 percent premium over the $24.04 closing price of Alpharma's common stock on Thursday. King actually first made the offer to Alpharma in a letter on Aug. 4 and said the offering represents a 49 percent premium, based on the share price that day.

The deal was only publicly disclosed Friday. Alpharma shares surged $10.86, or 45.2 percent, to $34.90 in premarket trading, suggesting the market considers Alpharma more valuable than King's offer.

"We believe this compelling combination would create a strong platform for sustainable long-term growth to better address the changing health care industry and provide meaningful, cost-effective medicines that improve the quality of life for patients," King Pharmaceuticals Chairman, President and Chief Executive Brian A. Markison said in a statement.

Representatives from Bridgewater, N.J.-based Alpharma could not be reached early Friday.

King is the third pharmaceutical company in the past month to propose a billion-dollar unsolicited buyout. On July 21, Roche offered $43.7 billion to buy the remaining shares of its cancer drug partner and biotech giant, Genentech Inc. Switzerland-based Roche already owns a majority stake in the South San Francisco, Calif.-based company. On July 31, New York-based Bristol-Myers Squibb Co. offered $4.5 billion to buy its cancer drug partner ImClone Systems Inc.

Both offers were unsolicited, and both were rejected as too low.

Shares of King Pharma fell 12 cents to $11.12 in premarket trading.