CIGARETTE-SMOKING DOES NOT AFFECT THIOPENTONE PHARMACODYNAMIC OR PHARMACOKINETIC BEHAVIOR

Purpose: Smoking affects the pharmacodynamic and pharmacokinetic behav iour of several drugs, in smokers, induction of anaesthesia is often s tormy. in this study we have determined whether cigarette smoking affe cted thiopentone tone pharmacodynamic or pharmacokinetic behaviour dur ing induction of anaesthesia. Methods: Fifteen smokers and 15 non-smok ers, scheduled for elective surgery, were studied. Heart rate, invasiv e arterial pressures and middle latency auditory evoked potentials wer e recorded awake and during thiopentone induction (9 mg.kg(-1) lean bo dy mass), before and after tracheal intubation. Blood was sampled up t o 24 hr after induction to measure thiopentone plasma concentrations a nd to calculate pharmacokinetic parameters. Results: Anaesthesia was a dequate in all patients, although haemodynamic intubation response was not blunted, Latencies or amplitudes of middle latency auditory evoke d potentials (MLAEP)did not differ between the groups, The postintubat ion latencies of Nb waves were 48.9 +/- 8.1 msec (mean +/- SD) in smok ers and 48.1 +/- 8.5 msec in nonsmokers. Pharmacokinetic data showed n o differences between smokers and non-smokers, Clearance of thiopenton e was 2.9 +/- 1.1 ml/min(-1).kg(-1) in smokers and 3.3 +/- 1.0 ml.min( -1) kg(-1) 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, respectiv ely. 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 1 89 +/- 20 mmHg and mean postintubation heart rates were 103 +/- 12 vs 102 +/- 17 beat per minute (bpm) in smokers and non-smokers, respectiv ely, Conclusion: We conclude, that cigarette smoking does not affect t he pharmacodynamic or pharmacokinetic behaviour of thiopentone.