A double blind comparison of alfentanil and fentanyl

Alfentanil and fentanyl were compared as supplements to thiopentone, nitrous oxide, relaxant anaesthesia in a randomised, double blind trial carried out on 55 adult patients undergoing elective surgery. The fentanyl-treated patients resumed spontaneous ventilation more rapidly at the end of anaesthesia (3 minutes) than the alfentanil-treated group (5.1 minutes, p less than 0.02). In other respects the drugs appeared indistinguishable. A computer model is used to explain why, despite the shorter elimination half-life, the alfentanil-treated patients did not awaken more rapidly than those in the fentanyl group.