Application of a new method for measurement of plasma methadone levels to the use of epidural methadone for relief of postoperative pain.
A method is described for measurement of plasma methadone concentrations using a gas chromatic technique that is rapid and specific and enables the detection of concentrations of less than 1 ng/ml in plasma samples of only 1 ml. The method, when used to determine the plasma methadone levels in patients given continuous epidural infusions of methadone plus on-demand supplementation for relief of postoperative pain, showed plasma methadone plateaus of around 10 ng/ml (starting at 15 min and lasting over 2 hr) and 20 ng/ml (starting at 3 hr and lasting over the period of treatment) (P less than 0.001) after an initial 2-mg methadone epidural bolus and with continuous epidural methadone. Mean plasma methadone levels of around 10 ng/ml were associated with pain relief. Analgesia could be safely maintained for 24 hr.
Magora
F
F
Department of Anesthesiology at Hadassah University Hospital, En Karem, Jerusalem, Israel.
Chrubasik
J
J
Damm
D
D
Schulte-Mönting
J
J
Shir
Y
Y
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002849:Chromatography, Gas / Q000379:methods; D005260:Female; D006801:Humans; D007268:Injections, Epidural; D008297:Male; D008691:Methadone / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D008875:Middle Aged; D010149:Postoperative Pain / Q000188:drug therapy*
D008691:Methadone