How long does Ambien stay in your system?? Answer this Question I seem to have no effect to ambien or Xanax. Rx 10mg ambien or 2mg. How long does Ambien stay in your system. Ambien is quick-acting, and with a normal dosage of 20mg its effects last up to four hours, but begins winding down. Variables that influence how long Ambien stays in your system to the dosage of Ambien they're taking) can affect systemic clearance. Usually.