<prompt> The shoest acting opioid is:-FentanylSulfentanilRemifentanilAlfentanyl  <response>: Fentanyl : Supplemental doses are to be given after 30 min only Analogues of feentanyl Sulfentanyl Alfentanyl Remifentanil Onset of Action : within 1-2 min IV injection Fades in : 10-15 min Sho action is due to rapid metabolism Metabolized by : Non specific esterases Extra hepatic,Extra renal Safe in fetus, can be used in labour as analgesic 