** Canadian Drugmaker's U.S.-listed shares up 6 pct at $116.50
** Shares rise after sliding 38 pct for four straight days that wiped out about $23 bln from the company's market cap
** The stock lost more than a quarter of its value on Wednesday after Citron Research alleged the company used specialty pharmacies to inflate revenue
** Valeant moved to reassure investors on Thursday by saying it would respond to allegations on an investor call on Monday.
** The company is under federal investigation for major price hikes on some drugs