By Sneha Banerjee and Carl O'Donnell (Reuters) - Valeant Pharmaceuticals International Inc will appoint an interim chief executive officer to replace Michael Pearson who is hospitalized, a source familiar with the matter told Reuters, news that sent shares down 7 percent on Tuesday. The source did not clarify whether the CEO would be temporary or would permanently replace Pearson, 56, who is recovering from a severe case of pneumonia. Pearson's hospitalization, disclosed on Dec. 25, is the latest challenge for the Canadian drugmaker whose shares have fallen nearly 60 percent since late August in the face of questions from Congress, investors and customers about how it prices and sells drugs.