Nicotine Fact Sheet 

Nicotine is a toxic, dependence-producing psychoactive drug found exclusively in the plant "Nicotiana tobacum". First isolated in 1828, nicotine is but one of thousands of constituents of the plant. In concentrated form, it is toxic; a few drops placed on the tongue can kill a person by paralysing the breathing process.

Pipes were initially the main instruments for tobacco smoking, followed by cigars. Other methods of use were inhalation of snuff (a fermented, fine tobacco powder) and tobacco chewing. In the mid-nineteenth century, new varieties of tobacco, changes in technology of curing the leaf, and machinery for mass production, facilitated the spread of a new product - the cigarette. Cheaper and neater than cigars, the cigarette yielded a milder smoke that could be inhaled.
 

Nicotine is absorbed through the mucous membrane of the nose and mouth when tobacco is chewed or snuffed and absorbed through the lung alveoli when smoked (the most common form of use). When a smoker inhales, the temperature at the tip of the cigarette rises to approximately 926oC. At this temperature, more than 4000 compounds are released. Tobacco smoke can be broken down into both gases and particulates. Gases include carbon monoxide, carbon dioxide, ammonia, volatile nitrosamines, hydrogen cyanide, and volatile hydrocarbons. The particulates are nicotine, water, and tar.

Most cigarettes contain between 0.5 and 2.0 mg of nicotine. Approximately 20% of this amount is inhaled and reaches the bloodstream. It has been estimated that a pack-a-day smoker delivers 73,000 puffs or doses of nicotine to the brain each year.

The effects of nicotine on the Central Nervous System (CNS) are complex. One of the actions involves the triggering of the release of brain chemicals which results in CNS stimulation. Dopamine, one of these chemicals, activates the reward or pleasure centre in the brain and may be responsible for the effects which reinforce continued use (and dependency).

Short-term physical effects of nicotine intake are:

• increased heart-rate

• constriction of blood vessels

• increased blood pressure

• drop in skin temperature

• reduction of circulation to legs and arms

• decrease in skeletal muscle tone

• stimulation of the brain stem's vomiting centre (a problem mainly for beginning smokers)

Include pleasure, increased alertness, improved mental function and task performance, decreased anxiety, and decreased appetite.

Long-term or chronic effects include:

• increased incidence of cancer of the lungs, throat and mouth (and some types of lung cancer are almost exclusive to smokers)

• increase in respiratory problems (allergy, infection) in non-smokers exposed to tobacco smoke

• increase in chronic lung diseases such as asthma and emphysema

• development of smoker's cough, bronchitis, inflammation of the airways, and more severe infections

• increase in blood lipid levels especially low density lipoprotein, LDL ("bad" cholesterol)

• increased blood thickness and greater probability of blockages

• babies of smoking women are smaller at all stages of development than babies of non-smokers

• increased incidence of premature delivery of babies by smoking mothers

• in females, earlier menopause resulting in greater risk of bone thinning

Nicotine withdrawal involves physiological, behavioural, and subjective changes. It is characterized by reports of:

• craving

• anxiety

• irritability

• hunger

• restlessness

• decreased concentration

• drowsiness

• sleep disturbance

• other symptoms reported include nervousness, lightheadedness, headaches, tremors, and nausea

These self-reported withdrawal symptoms peak during the first 1-2 weeks after smoking cessation. Most of the symptoms disappear within a month. Craving can continue for a longer period. The severity of the withdrawal may be associated with the level of previous nicotine intake but at present, evidence of that relationship is considered unreliable and weak.

Drug Dependency Services, Central Region, 1999