Because nicotine from smokeless tobacco is absorbed through the mouth, it takes longer to produce an effect than if it were absorbed through the lungs. But using cigarettes and smokeless tobacco really do result in the same amount of nicotine intake.
"Youth and Tobacco: Preventing Tobacco Use among Young People. A Report of the Surgeon General." Department of Health and Human Services. Washington, DC. 33. Web.
Adolescents who use smokeless tobacco are more likely to become cigarette smokers.
"Preventing Tobacco Use Among Young People: A Report of the Surgeon General." U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevetion, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health. 17. Web.
An average of 4.5mg of nicotine is absorbed from 7.9g of chewing tobacco and an average of 3.6mg of nicotine is absorbed from 2.5g moist snuff.
Severson, H.H. "What Have We Learned From 20 Years of Research on Smokeless Tobacco Cessation?" American Journal of Medical Sciences. 326(4). Oct. 2003: 206-211. Web.
Ammonia boosts the impact of nicotine.
"Smoking and Tobacco Control." U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health, National Cancer Institute. Risks Associated with Smoking Cigarettes with Low Machine-Measured Yields of Tar and Nicotine. 19 Nov. 2001: 174.