title: Pharmacokinetics of tramadol in children after i.v. or caudal epidural administration.
abstract: We have studied the pharmacokinetics of a single bolus dose of tramadol 2 mg kg-1 injected either i.v. or into the caudal epidural space in 14 healthy children, aged 1-12 yr, undergoing elective limb, urogenital or thoracic surgery. Serum concentrations of tramadol and its metabolite O-demethyl tramadol (MI) were measured in venous blood samples at various intervals up to 20 h by non-stereoselective gas chromatography with nitrogen-selective detection. All pharmacokinetic variables were evaluated using a non-compartmental model. After a single i.v. injection (n = 9), the mean elimination half-life of tramadol was 6.4 (SD 2.7) h, with a volume of distribution of 3.1 (1.1) litre kg-1 and total plasma clearance of 6.1 (2.5) ml kg-1 min-1. All of these pharmacokinetic variables were similar to those reported previously in adults. After caudal epidural administration (n = 5), mean elimination half-life was 3.7 (0.9) h, volume of distribution was 2.0 (0.4) litre kg-1 and total clearance was 6.6 (1.9) ml kg-1 min-1. The caudal/i.v. quotient of the AUC was 0.83, which confirms that there is extensive systemic absorption of tramadol after caudal administration. Serum concentrations of MI showed a time course typical of a metabolite after both modes of administration. Serum concentrations of MI after caudal administration were lower than those after i.v. injection.
authors.affiliation: Royal Liverpool Children's NHS Trust, UK.
authors.forename: B V
authors.initials: BV
authors.lastname: Murthy
authors.forename: K S
authors.initials: KS
authors.lastname: Pandya
authors.forename: P D
authors.initials: PD
authors.lastname: Booker
authors.forename: A
authors.initials: A
authors.lastname: Murray
authors.forename: W
authors.initials: W
authors.lastname: Lintz
authors.forename: R
authors.initials: R
authors.lastname: Terlinden
mesh_terms: D000698:Analgesia / Q000379:methods*; D015360:Analgesia, Epidural / Q000379:methods; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D002648:Child; D002675:Child, Preschool; D006207:Half-Life; D006801:Humans; D007223:Infant; D007275:Injections, Intravenous; D014147:Tramadol / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000097:blood* / Q000493:pharmacokinetics
chemical_list: D000701:Analgesics, Opioid; C080580:O-demethyltramadol; D014147:Tramadol