My Son Will Run Out Of His Rx For Vallium

My son will run out of his Rx for Vallium in three days. He takes 10 mg at night and 1 mg in the morning. I don't have an appointment to see his new psychiatrist until Nov. 13. What will his side effects be, if he has to stop his medication this week? He is 17 years old, 195 lbs. and 5' 7'' tall.