PHARMACOKINETICS OF FENTANYL DURING CONSTANT RATE I.V. INFUSION FOR THE RELIEF OF PAIN AFTER SURGERY

Forty-five patients in four groups undergoing orthopaedic, upper abdominal, prolonged or cardiac surgery received a constant rate i.v. infusion of fentanyl 100 μg h −1 for 24 h starting 2 h before surgery. A single bolus dose was given i.v. at the induction of anaesthesia. Plasma fentanyl concentrations, measured by radio-immunoassay were between 1 and 3 ng ml −1 until the infusions were discontinued. Clearance of fentanyl was decreased in the cardiac surgery group only. The elimination half-life was 7.3–9.7 This simple regimen produced effective analgesia.