Some patients may develop Vytorin^® side effects that include upper respiratory infections, general feeling of weakness, and increased liver enzymes. While most side effects do not require medical attention, if you experience unexplained muscle pain, tenderness, or weakness with a fever or general feeling of sickness, contact your healthcare provider immediately, because it could be a sign of a much more serious problem. Other potential side effects that may require immediate medical attention include trouble breathing, passing brown or dark-colored urine, nausea or vomiting, and unexplained rash.