In chronic alcoholics, while they consume ethanol, an increase in the oxidative hepatic metabolism is produced by means of an increment of microsomal enzymes induced by ethanol. In our study we have appraised this hepatic metabolism during the period of acute ethilic abstinence. This study has been performed in 20 chronic alcoholics without clinical symptoms, after five days free of ethanol drinks. The assessment of oxidative hepatic metabolism was realized by means of the measuring of corporal antipyrine clearance (by saliva elimination), being compared to those performed in a control group of ten healthy adults. Antipyrine clearance (5.5 +/- 2 l/h) is increased significatively in chronic alcoholics respect to the control group value (3.4 +/- 1 l/h) (p < 0.01). Elimination half-life of antipyrine in chronic alcoholic groups (7.6 +/- 3 h) is decreased significatively respect to the control group value (11.2 +/- 2 h) (p < 0.01). During the period of acute abstinence, the oxidative hepatic metabolism persists increased. In these patients, when we administer drugs with hepatic metabolism following the same metabolic way that antipyrine, it will be necessary to readjust the maintenance dose to attain its therapeutic effect.