title: Pharmacokinetics and postoperative analgesia of epidural tramadol: A prospective, pilot study.
abstract: BACKGROUND
  Tramadol, a centrally acting analgesic drug, can be administered via multiple routes and is generally well tolerated.
  
  
  OBJECTIVE
  This study was designed to assess the pharmacokinetics of epidural tramadol administered preoperatively in Japanese patients undergoing upper abdominal surgery.
  
  
  METHODS
  Japanese patients who were scheduled to undergo upper abdominal surgery in The Kitasato Institute Hospital, Tokyo, Japan, were included. Patients received tramadol 2 mg/kg with 5 mL of 1% mepivacaine epidurally 10 minutes before incision. The serum concentration of tramadol was determined by high-performance liquid chromatography for 21 hours after administration. Serum concentration was determined before tramadol administration and 10, 20, 30, and 60 minutes after tramadol administration, first postoperative night, and first postoperative day. Pain score and adverse events (AEs) were assessed at 1, 3, 6, 12, 18, 24, 36, and 48 hours after surgery by patient interview.
  
  
  RESULTS
  Eleven patients were assessed for enrollment. Seven patients (6 men, 1 woman; mean [SD] age, 61.3 [12.6] years; mean [SD] weight, 59.9 [8.9] kg) provided consent and completed the study. The mean (SD) serum Cmax of tramadol was 1385.5 (390.8) ng/mL, Tmax was 0.33 (0.22) hour, and terminal elimination half-life (t1/2β) was 10.5 (2.3) hours. Four patients complained of nausea; however, only 1 patient was administered an antiemetic. No other AEs were reported.
  
  
  CONCLUSIONS
  This pilot study found that epidural tramadol administered before incision induced a Cmax within 30 minutes of administration. The drug was detected in serum at ∼21 hours after surgery.
authors.affiliation: Division of Clinical Pharmacy, Center for Clinical Pharmacy and Clinical Sciences, School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan.
authors.forename: Rie
authors.initials: R
authors.lastname: Kubota
authors.affiliation: Division of Clinical Pharmacy, Center for Clinical Pharmacy and Clinical Sciences, School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan.
authors.forename: Takako
authors.initials: T
authors.lastname: Komiyama
authors.affiliation: Department of Anaesthesia, The Kitasato Institute Hospital, Tokyo, Japan.
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Miwa
authors.affiliation: Division of Clinical Pharmacy, Center for Clinical Pharmacy and Clinical Sciences, School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ide
authors.affiliation: Department of Surgery, The Kitasato Institute Hospital, Tokyo, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Toyoda
authors.affiliation: Department of Surgery, The Kitasato Institute Hospital, Tokyo, Japan.
authors.forename: Fumiki
authors.initials: F
authors.lastname: Asanuma
authors.affiliation: Department of Surgery, The Kitasato Institute Hospital, Tokyo, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Yamada
keywords: epidural; pharmacokinetics; tramadol