Pharmacokinetic evaluation of haemoperfusion in phenobarbital poisoning

Charcoal haemoperfusion was performed for 5-12 h in three patients with maximal plasma phenobarbital concentrations of 600, 946 and 1044 mumol/l (138, 217 and 240 micrograms/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 1.1-1.21/kg. This is clear evidence for recommending haemoperfusion in cases of serious poisoning with phenobarbital.