Valeant Pharmaceuticals International Inc shares fell as much as 20 percent on Thursday to a level not seen since 2013, heaping new pressure on Chief Executive Officer Michael Pearson after weeks of steep losses due to concerns about the drugmaker's business practices. The ticker information for Valeant Pharmaceuticals International Inc. is displayed on a screen above the post where it's traded on the floor of the New York Stock Exchange November 4, 2015.