Nicotine

Nicotine is derived from tobacco, which is one of the family of plants nicotiana, which includes tomatoes, belladonna, and petunias.

After several voyages, Columbus and others introduced tobacco to Europe and it was listed as a cure for every known disease at the time.

Cigarettes account for 95% of all tobacco use in the US. In the 1800's, people might smoke 40 cigarettes a year...now heavy smokers smoke that many in a day.

Each cigarette delivers around 1 mg of nicotine...70 mg is fatal. Chewable tobacco delivers about 4.5 mg of nicotine and a pinch of snuff between the cheek and gums gives you 4.5 mg.

Many smokers report a sense of relaxation when they smoke a cigarette. This isn't the cigarette. They are relieving their withdrawal symptoms.

Metabolism

Cigarette smoke can interact with psychotropic medications via the P450 system. Nicotine itself is metabolized primarily through 2A6. There are a number of unsavory ingredients in cigarette ★smoke.

Neurochemical

Remember that nicotine causes upregulation of nicotinic acetylcholine receptors and when these aren't occupied, one feels irritable and restless. In addition, nicotine causes a release of endorphins and dopamine, which makes it quite addictive. Nicotine also appears to decrease appetite and increase metabolism, which is why smokers tend to weigh less than nonsmokers.

Tolerance to nicotine develops rapidly, more rapidly than heroin or cocaine.