BACKGROUND:  Few data are available on the stereoselective pharmacokinetics of tramadol in children.

Purpose: was to develop a population pharmacokinetic model for the (+)- and (-)-enantiomers of tramadol and its O-demethyl tramadol metabolite (M1) in children.

METHODS: Twenty-five children (1-8 yr) were included in this study. Tramadol was administered after surgery by continuous infusion (loading dose, 2 mg kg(-1) i.v. over 10 min followed by continuous infusion of 8 mg kg(-1) over 24 h). If pain relief was inadequate, additional 1 mg kg(-1) i.v. bolus doses of tramadol were given over 10 min. A two-compartment structural model was used with NONMEM.

RESULTS: 

CONCLUSIONS:  The results of this study combine relationships between tramadol CL and patient covariates that may be useful for dose adjustment. Polymorphism is likely to contribute to the interpatient variability observed in the AUC M1/AUC tramadol ratios.