Components of Tobacco Smoke

Inhaled nicotine reaches the brain within 15 seconds and concentrations in brain tissue remain high for about 2 hours

Nicotine is transformed by oxidation in the liver to conitine which is then excreted in the urine where it can be detected by a laboratory test

In the brain, it activates the dopamine reward system and increases certain neurotranmitters and hormones including norepinephrine, epinephrine , endorphins, and acth/cortisol.

Other activators of the dopamine reward system include opiates, amphetamines, and cocaine.

Nicotine is 10 times more potent than heroin in its addictive properties.

Nicotine improves attention, learning, reaction time, problem solving ability, lifts the mood, decreases tension, and lessens depressive feelings

Skeletal muscles: promotes relaxation of muscle tone

Digestive tract: nausea and appetite suppression

Respiratory system: local irritation, impaired ciliary motion which impacts the auto-cleaning mechanisms of the lungs

Cardiovascular effects: increases heart rate and blood pressure, Platelet adherence and vasoconstriction resulting in abnormally active clotting of the blood and accounts for the increased risk for stroke and heart disease

Average dose of nicotine delivered by smoking one cigarette is about 0.5 mg
Fatal dose of nicotine is 60 mg and causes respiratory muscle paralysis

Nausea, vomiting, salivation, pallor, weakness, abdominal pain with diarrhea, dizziness, headache, increased blood pressure and heart rate, tremor, cold sweats, decreased ability to concentrate, confusion and sensory-perceptual disturbances.

Symptoms include nicotine craving, tension, irritability, depressed mood, insomnia, difficulty concentrating, restlessness, decreased heart rate and blood pressure, weight gain and decreased motor performance.

Symptoms can develop within hours of smoking last cigarette and can last for weeks. Withdrawal is often worse in the evening. Weight gain may occur.

Craving may be more intense with nicotine tapering than with cold turkey quitting...

The biochemistry of nicotine is complex mainly because the part of the nervous system called the sympathetic system has receptor sites that interact with nicotine and are called nicotininc receptors. Another subset of receptors are called muscarinic receptors.

Nicotine stimulates the nicotininc receptors and in turn increases alertness, quickens the heart rate, raises the blood pressure etc..

Over time as a smoker keeps giving the body nicotine, the body learns to adapt to the extra stimulation by modifying the number of receptors and by decreasing production of the chemicals the body produces that would naturally stimulate these receptors. This is why new smokers feel ill but then develop tolerance to nicotine.

When a smoker quits, the person is left with an abnormally small number of receptor sites and a diminished supply of the natural neurotransmitters that ordinarily stimulate these receptors. This accounts for the withdrawal effects. Receptors turnover times are slow...3-6 weeks or more with individual variations. Giving nicotine thru a patch or gum or nasal inhaler helps the body maintain the previous status quo where it relied on nicotine to stimulate the receptors. As the dose of nicotine is tapered the body slowly manufactures more receptors and more neurotransmitters and withdrawal effects begin to abate .

Nicotine replacement slows the process of returning the body's natural sympathetic system to normal, yet makes for a generally more comfortable withdrawal...so there are trade offs either way.

Cigarette smoke has both gaseous and particulate phases

Inhaled smoke delivers chemicals to the bloodstream of the smoker and deposits chemicals and particules in the smoker's mouth, bronchial airway passages and in the lungs

Mainstream smoke comes from the mouthpiece during puffing as the smoker exhales

Sidestream smoke is generated between puffs from the burning cone and mouthpiece

Environmental tobacco smoke is pollution from the mainstream and sidestream smoke and is harmful to the smoker and those who inhale it, as is discussed in this article: Environmental Tobacco Smoke by the American Cancer Society

Environmental Tobacco Smoke : Link to a NIH paper discussing effects of passive smoking (i.e. inhaling environmental tobacco smoke). . .

Smoke composition varies with the
. . .type of tobacco
. . .curing method
. . .temperature of combustion (pyrolysis)
. . .length of the cigarette
. . .paper characteristics
. . .additive, contaminants, filters


More than 4000 identified constituents are present in cigarette smoke

nicotine which is a toxic alkaloid and accounts for the addictive properties of tobacco

carbon monoxide

Carcinogens:
polynuclear aromatic hydrocarbons
aromatic amines, nitrosamines
tar
benzo(a)pyrene
vinyl chloride

Cocarcinogens: catechol, phenol, cresol

Ciliotoxins and pulmonary irritants

radioactive compounds


• The Toxicology of Cigarette Smoke and Environmental Tobacco Smoke
  A report by Stephen Mulcahy with all the details of smoke composition.

• Nicotine Addiction
  
  

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