Pharmacokinetics of rectal tramadol in postoperative paediatric patients.

Postoperative analgesia in children may be improved by using tramadol. The pharmacokinetics of rectal tramadol in young children were therefore investigated.The pharmacokinetics of rectal tramadol and its active metabolite were studied in 12 young children (age: 1-6 yr) postoperatively. On the basis of these data, a population model was constructed. Using this model, the pharmacokinetics of different doses of tramadol were calculated.The pharmacokinetics of rectal tramadol could be adequately described by a one-compartment model. The pharmacokinetic parameters derived from the model indicate that a low variability was present. Elimination half-life was 4.3 (0.2) h (sem) and the apparent clearance was 16.4 (1.5) litre h(-1) (sem).The study showed that after rectal administration, tramadol is absorbed at a reasonable rate and with a low inter-individual variability in small children. The data also suggested that a rectal dose of tramadol 1.5-2.0 mg kg(-1) is therapeutic.