Nicotine pharmacodynamics: some unresolved issues

This paper focuses on some issues in the field of nicotine pharmacodynamics in which widely held suppositions have outstripped the supporting evidence. It considers how far the view that nicotine acts as a stimulant in low doses and as a sedative in higher doses is supported by the data and concludes that within the range of doses ingested by cigarette smokers, only stimulant actions have been reliably observed. It examines evidence for the view that nicotine improves ability to sustain attention and concludes that a positive effect of nicotine not attributable to relief of a withdrawal deficit has yet to be demonstrated. Finally, it considers the issue of physiological tolerance and argues that ideas concerning a role for chronic tolerance in nicotine dependence have yet to be supported empirically. Despite advances in our understanding of nicotine's effects in recent years there is still much work to be carried out before fundamental issues underlying its addictive potential can be resolved.