['To study the toxicokinetics in severe chloroquine poisoning, and to evaluate the efficacy of hemoperfusion.', 'Case report on one observation.', 'Medical intensive care unit (ICU) of the University Medical Center Utrecht, The Netherlands.', 'A previously healthy, 52-yr-old woman ingested 100 tablets containing 100 mg chloroquine base 1 hr before admission. At admission, she was drowsy, agitated, hypotensive, and in respiratory distress. Shortly thereafter, she was resuscitated from cardiac arrest. After hemodynamic and respiratory stabilization, the patient was transferred to the medical ICU. TOXICOKINETICS EVALUATION: During the course of her stay at the ICU, blood samples were taken for the determination of chloroquine and the metabolite desethylchloroquine concentration. Hemoperfusion was started 3.5 hrs after ingestion of the chloroquine tablets.', 'The following toxicokinetics data during this severe chloroquine poisoning were calculated: apparent volume of the central compartment 181 L, apparent volume of distribution 1137 L, half-life in the distribution phase 6.4 hrs, half-life in the elimination phase 392.8 hrs, and total body clearance 2.01 L/hour. The average extraction ratio during hemoperfusion was 0.07, 0.28, and 0.25, in plasma, erythrocytes and whole blood, respectively. The total amount of chloroquine removed by hemoperfusion was only 480 mg (5.3% of the amount ingested). Simulation of a hemoperfusion session over 5 hrs by using a column with an optimal extraction ratio of 1.0 would have removed 1,816 mg chloroquine, only 18.2% of the amount ingested. This limited contribution of hemoperfusion to the total clearance makes it ineffective.'] Is hemoperfusion ineffectual in severe chloroquine poisoning?