* Net Q2 adjusted EPS $1.44 vs Street $1.31
* Sales up 11 pct to $539 mln
* Shares down about 4 pct (Adds analyst comments, expectations, sales details, share move)
By Bill Berkrot
NEW YORK, Aug 4 (Reuters) - Cephalon Inc CEPH.O posted a better-than-expected second quarter profit on Tuesday on increased sales of its flagship sleep disorder drug and newer medicines, but issued a third-quarter earnings forecast that disappointed investors and its shares fell about 4 percent.
Cephalon maintained its full-year sales forecast of $2.18 billion to $2.23 billion. For the third quarter it expects sales of $540 million to $560 million, with adjusted earnings of $1.45 to $1.55 per basic share.
"It's a little light on Q3 EPS," said Jefferies & Co analyst David Windley.
The company's shares, which closed at $59.95 on Nasdaq, fell to $57.65 in extended trading.
Cephalon posted second-quarter net profit of $84.8 million, or $1.11 per share, compared with a profit of $51.9 million, or 69 cents per share, a year ago.
Excluding items, the Frazer, Pennsylvania-based company had adjusted earnings of $1.44 per share, exceeding analysts' average expectations by 13 cents, according to Reuters Estimates.
Sales rose 11 percent to $539 million, with total revenue of $547.8 million topping Wall Street estimates of $541 million.
Worldwide sales of the sleep disorder drug Provigil rose 12 percent to $262.1 million, while the just launched Provigil follow-up drug Nuvigil had sales of $16.8 million.
"For all the hoopla that people have raised about what's going to happen when Provigil goes generic three years from now, I'd say we've got a long time to worry about that and they've got all the pieces in place to reduce the reliance on Provigil," said Natixis Bleichroeder analyst Corey Davis.
"In the meantime, you can rest assured you're going to get 20 to 25 percent growth for the next three years," he added.
Cephalon's new cancer drug Treanda saw sales climb to $55.8 million, up from $50.2 million in the previous quarter.
Sales of Actiq for cancer pain fell 27 percent to $37.9 million in the face of generic competition. That was partially offset by $30.9 million in sales from the new muscle relaxer Amrix, up 80 percent from a year ago and 18 percent from the first quarter.
Davis said Treanda sales appear to have taken a pause from their rapid growth, but he does not expect that to last.
"The feedback I've been getting from the field is people are very, very happy with its performance," he said. (Reporting by Bill Berkrot; editing by Andre Grenon, Bernard Orr)