Impact of menthol on oral nicotine consumption in female and male Sprague Dawley rats.

Introduction: One of the most preferable flavors in oral nicotine delivery systems is menthol which masks the harshness of tobacco. However, possible interactions between oral menthol and nicotine on intake and preference remain unclear. Therefore, we aimed to determine the impact of menthol on oral nicotine consumption.

Methods: Adult Sprague Dawley female and male rats (n=8/per group) were given a choice of water or drug solution by using two-bottle free choice paradigm for two weeks: vehicle (5% ethanol), nicotine (20 mg/l), menthol (1 g/l) and mentholated nicotine groups. At the end of the study, plasma nicotine levels were determined.

Results: When rats were given a choice of nicotine or water, nicotine intake was similar between female and male rats. Menthol addition to nicotine solution significantly increased nicotine intake and preference in male but not female rats without a considerable effect on total fluid intake and body weight change in either sex. The average nicotine intake in male rats was 0.5 ± 0.05 and 1.4 ± 0.12 mg/kg/day for nicotine and menthol-nicotine combination (p<0.05), respectively. The average nicotine intake in female rats was 0.6 ± 0.05 and 0.6 ± 0.03 mg/kg/day for nicotine and menthol-nicotine combination (p>0.05), respectively. Plasma nicotine levels were not significantly different between the groups in either male (nicotine group: 20.8 ± 4.9, mentholated nicotine group: 31.9 ± 3.2 ng/ml) or female (nicotine group: 24.0 ± 3.3, mentholated nicotine group: 17.8 ± 2.9 ng/ml) rats (p>0.05).

Conclusions: Menthol increases oral nicotine consumption in male, but not female, rats.

Implications: This study may provide data on the co-use of menthol and nicotine in the smokeless tobacco, particularly oral dissolvable tobacco products.