As nicotine enters the body, it is distributed quickly through the bloodstream and can cross the blood-brain barrier. On average it takes about seven seconds for the substance to reach the brain. The half life of nicotine in the body is around 2 hours. The amount of nicotine inhaled with tobacco smoke is a fraction of the amount contained in the tobacco leaves as heat destroys the substance. The amount of nicotine absorbed by the body from smoking depends on many factors, including the type of tobacco, whether the smoke is inhaled, and whether a filter is used. For chewing tobacco, often called dip, or snuff, which is held in the mouth between the lip and gum, the amount released into the body tends to be much greater than smoked tobacco.
Nicotine increases the activity of nicotinic acetylcholine receptors, leading to an increased flow of adrenaline, a stimulating hormone. The release of adrenaline causes an increase in heart rate, blood pressure and respiration, as well as higher glucose levels in the blood. Cotinine is a break-down product of nicotine which remains in the blood for up to 48 hours and can be used as an indicator of a person’s exposure to smoke. In high doses, nicotine will cause a blocking of the nicotinic acetylcholine receptor, which is the reason for its toxicity and its effectiveness as an insecticide.
It has been noted that the majority of people diagnosed with schizophrenia smoke tobacco. 75% to 90% of schizophrenics smoke it is estimated. It is argued that the increased level of smoking in schizophrenia may be due to a desire to self-medicate with nicotine. More recent research has found the reverse, that it is a risk factor without long-term benefit, used only for its short term effects. Research on nicotine as administered through a patch or gum is ongoing.
