Omthera Pharmaceuticals, Parametric Sound, Valeant Pharmaceuticals, Green Mountain Coffee Roasters, Seadrill, Citigroup, Ford Motor, DRDGOL, Royal Caribbean Cruises and Exelon Corp. are among the companies whose shares are moving in pre-market trading on Tuesday.

Omthera Pharmaceuticals Inc. (NASDAQ:OMTH) stock rallied 87.59 percent to $12.70 in pre-market trading. AstraZeneca announced on Tuesday that it has entered into a definitive agreement to acquire Omthera Pharma for approximately $443 million.

Parametric Sound Corp. (NASDAQ:PAMT) stock rallied 17.98 percent to $21.00 in pre-market trading. The stock has a 52-week low of $3.49, a 52-week high of $22.39 and $118.83 million in market capitalization.

Valeant Pharmaceuticals Intl Inc. (NYSE:VRX) stock climbed 7.73 percent to $91.00 in pre-market trading. Valeant Pharma and Bausch & Lomb Holdings Inc announced on Monday that they have entered into a definitive agreement under which Valeant will acquire Bausch & Lomb for $8.7 billion in cash.

Green Mountain Coffee Roasters Inc. (NASDAQ:GMCR) stock surged 3.96 percent to $74.75 in pre-market trading. The stock has a 52-week low of $17.11, a 52-week high of $81.70 and $10.73 billion in market capitalization.

Seadrill Ltd. (NYSE:SDRL) stock gained 2.96 percent to $41.10 in pre-market trading. The company reported first quarter net profit of $440 million or $0.88 per share, above Reuters' estimate of $0.58 per share for the quarter.

Citigroup Inc. (NYSE:C) stock gained 1.54 percent to $51.30 in pre-market trading. The stock has a 52-week low of $24.61, a 52-week high of $52.89 and $153.73 billion in market capitalization.

Ford Motor Co. (NYSE:F) stock advanced 1.35 percent to $14.99 in pre-market trading. The stock has a 52-week low of $8.82, a 52-week high of $15.32 and $58.14 billion in market capitalization.

DRDGOLD Ltd. (NYSE:DRD) stock declined 2.17 percent to $5.40 in pre-market trading. The stock has a 52-week low of $5.05, a 52-week high of $8.59 and $209.31 million in market capitalization.

Royal Caribbean Cruises Ltd. (NYSE:RCL) stock declined 1.74 percent to $35.50 in pre-market trading. The company announced that the May 31, 2013 sailing of Grandeur of the Seas from Baltimore, Maryland, will be cancelled to allow for repairs to damages sustained as a result of a fire. 

Exelon Corp. (NYSE:EXC) stock declined 1.30 percent to $34.20 in pre-market trading. The company stock was downgraded to “hold” rating from “buy” rating by Deutsche Bank with a new price target of $34.00.