Hello Jana,   Short answer, yes, it can.    Vytorin is a combination pill of simvistatin and ezetimibe.  Ezetimibe is a cholesterol binding agent in your intestines.  When this happens, it can increase in some people the amount of cholesterol and water that remain in your stool.  Diarrhea is a common side effect in patient taken ezetimibe alone, so it makes sense that the combination pill would have the same effect.   If your loose stool persist or worsten, you should discuss with your doctor this unpleasant side effect.  He will likely change you to a pure statin medication.   To your health, Neil MD