Valeant Pharmaceuticals International Inc (VRX.TO)(VRX.N) on Monday said a group of company executives will immediately take over for its chief executive officer until he returns from medical leave, news that sent its shares tumbling 10 percent. The Canadian company said CEO Michael Pearson, 56, was being treated for severe pneumonia. A spokeswoman for Valeant, based in Laval, Quebec, declined to comment on the decision to appoint a trio to take over for Pearson.