Common side effects (occurring in 5 or more out of 100 patients and less than 10 in 100 patients) include: herpes simplex (cold sores), sinus infection (sinusitis), viral infection, stomach flu (gastroenteritis), lung infection, insomnia, cough, sore throat, bloody nose, abdominal pain, constipation, vomiting, upper abdominal pain, itchy skin, rash, muscle aches, pain in the limbs (arms and legs), muscle cramp, fatigue, and influenza-like illness.