Pharmacokinetic evaluation of haemoperfusion in phenobarbital poisoning

Abstract

Charcoal haemoperfusion was performed for 5–12 h in three patients with maximal plasma phenobarbital concentrations of 600, 946 and 1044 µmol/l (138, 217 and 240 µg/ml). During haemoperfusion with constant blood flow phenobarbital elimination followed first order kinetics with half-lives of 11.1, 10.0 and 7.2 h, respectively. After termination of the haemoperfusion there was no rebound effect in plasma phenobarbital concentration and the elimination was first order with half-lives of 51, 82 and 48 h, respectively. Thus, the plasma phenobarbital half-life was reduced by 78–88% during haemoperfusion. In the same period 76–86% of the total body clearance of phenobarbital was due to the haemoperfusion column at a calculated volume of distribution of phenobarbital of 1.1–1.2 l/kg. This is clear evidence for recommending haemoperfusion in cases of serious poisoning with phenobarbital.