Cigarette smoking does not affect thiopentone pharmacodynamic or pharmacokinetic behaviour

Smoking affects the pharmacodynamic and pharmacokinetic behaviour of several drugs. In smokers, induction of anaesthesia is often stormy. In this study we have determined whether cigarette smoking affected thiopentone pharmacodynamic or pharmacokinetic behaviour curing induction of anaesthesia.

Fifteen smokers and 15 non-smokers, scheduled for elective surgery, were studied. Heart rate, invasive arterial pressures and middle latency auditory evoked potentials were recorded awake and during thiopentone induction (9 mg.kg-1 lean body mass), before and after tracheal intubation. Blood was sampled up to 24 hr after induction to measure thiopentone plasma concentrations and to calculate pharmacokinetic parameters.

Anaesthesia was adequate in all patients, although haemodynamic intubation response was not blunted. Latencies or amplitudes of middle latency auditory evoked potentials (MLAEP) did not differ between the groups. The postintubation latencies of Nb waves were 48.9 +/- 8.1 msec (mean +/- SD) in smokers and 48.1 +/- 8.5 msec in non-smokers. Pharmacokinetic data showed no differences between smokers and non-smokers. Clearance of thiopentone was 2.9 +/- 1.1 ml.min-1.kg-1 in smokers and 3.3 +/- 1.0 ml.min-1.kg-1 in non-smokers and elimination half life of thiopentone was 12.5 +/- 6.3 hr in smokers and 10.7 +/- 3.1 hr in non-smokers, respectively. The haemodynamic response after the induction dose of thiopentone and after tracheal intubation were similar in smokers and non-smokers. Mean postintubation systolic arterial pressures were 192 +/- 35 vs 189 +/- 20 mmHg and mean postintubation heart rates were 103 +/- 12 vs 102 +/- 17 beat per minute (bpm) in smokers and non-smokers, respectively.

We conclude, that cigarette smoking does not affect the pharmacodynamic or pharmacokinetic behaviour of thiopentone.