Effect of halothane anaesthesia on salivary elimination of paracetamol

The effect of halothane anaesthesia on paracetamol elimination was studied in 6 male patients undergoing short surgical procedures. Seven males operated on for the same indications under epidural anaesthesia served as the control group. Paracetamol concentration in saliva was measured at intervals on the day before and after surgery. Paracetamol t1/2 significantly decreased from 2.1 to 0.96 h and clearance rate (CL) significantly increased from 8.7 to 17.0 ml min-1 kg-1, when compared with the preoperative values. The control group also showed a significant but smaller alteration in the parameters. The results suggest that halothane anaesthesia per se may enhance the hepatic metabolism of paracetamol.