The effects of gender and menopause on serum lidocaine levels in smokers.

It has been established that human cytochrome P450 (CYP) enzymatic activity is affected by gender, or by hormonal factors such as the menopause in women. Gender differences have a more pronounced effect on cytochrome (CYP) 3A4 isoenzyme activity, whereas cytochrome (CYP) 1A2 isoenzyme activity is mainly induced by chronic smoking. Lidocaine is frequently used in the treatment of hemodynamic changes following laryngoscopy and tracheal intubation during general anesthesia, and is metabolized by CYP3A4 and CYP1A2 isoenzymes in the liver. The aim of this study was investigate the effects of gender and menopause on serum lidocaine levels in smokers under general anesthesia. Six men, six premenopausal women and six postmenopausal women were enrolled in the study and received i.v. lidocaine (1 mg/kg) 1 minute before they underwent general anesthesia. Serum lidocaine concentrations were measured using the EMIT method at 1, 5, 10, 20, 40 and 60 minutes post-administration. Statistical analyses were performed using the Mann-Whitney U-test. No statistically significant differences were found regarding the area under curve (AUC(0-60) microg/mL/min), elimination half-life (t1/2 [min]) of lidocaine and in the measured levels of serum lidocaine at any time point between the study groups (p > 0.05). These results suggest that gender and menopause may have no significant effect on serum lidocaine levels in smokers.