Background: Carbamazepine poisoning can be life threatening. The role and efficacy of extracorporeal drug clearance is not clearly defined.
Case report: A 16-year-old male ingested 34g of slow-release carbamazepine. His course was complicated by seizures, recurrent cardiac arrests, and renalfailure. Intestinal ileus at the time of presentation prevented effective gastrointestinal decontamination. His carbamazepine concentration peaked at 93.8 mg/L (397micromol/L) 106 hours after ingestion. There was evidence suggesting ongoing absorption for 120 hours. He underwent seven episodes of charcoal hemoperfusion for a total of 109.25 hours. He subsequently made a full recovery.
Methods: The efficacy of charcoal hemoperfusion was evaluated by measuring the carbamazepine concentrations in the afferent and efferent loops of the hemoperfusion cartridge using 17 paired convenience samples. Extraction ratios were calculated and plotted against timefor each individual episode of charcoal hemoperfusion.
Conclusion: The extraction ratio was linearly related to time, and ranged 0.46-0.02. The peak clearance was 69 mL/min. Cartridge saturation was defined as a clearance that was equal to an estimate of the patient's intrinsic clearance. In our patient, this was equivalent to an extraction ratio of 0.2 at a flow rate of 150 mL/min. By this definition, cartridge saturation appeared to occur at 7 hours. Charcoal hemoperfusion was associated with a significant reduction in the apparent half-life, which is most easily explained by clearance from the central vascular compartment, during a prolonged absorptive phase. The patient made full recovery without evidence of neurological deficit.