This video presents information on
the biological and psychological characteristics
of tobacco dependence and nicotine
addiction and withdrawal.
Tobacco dependence is not just a habit.
It's a chronic medical condition that
requires treatment, similar to alcohol or drug addiction.
Tobacco use can lead to tobacco dependence, which
is characterized by a physiological dependence
due to nicotine addiction, and a behavioral pattern of using
tobacco.
Nicotine is the drug in cigarettes and other tobacco
products that causes them to be addictive.
The repeated use of tobacco products over time
causes a person to become a physically
and psychologically dependent on them.
Nicotine is a natural ingredient in tobacco.
The amount of nicotine in a tobacco product
varies widely, depending on the type of tobacco product,
as well as where it's produced.
For example, a typical cigarette manufactured
in the United States contains about 10 milligrams
of nicotine.
However, cigarettes in India contain
around 15 milligrams of nicotine,
and bidis contain around 27 milligrams.
When tobacco is burned, tar droplets
are produced and inhaled into the lungs.
Nicotine travels into the lungs on the tar droplets,
enters the alveoli, and is absorbed
across the respiratory epithelial cells
to enter the pulmonary venous circulation,
moving into the systemic arterial circulation.
About one milligram of nicotine is ultimately
absorbed from one cigarette.
It's estimated that five milligrams of nicotine per day
can facilitate an addiction to tobacco products.
When smokeless tobacco is placed in the mouth
or inhaled through the nose, the nicotine
is absorbed and delivered into the bloodstream.
Nicotine levels in smokeless tobacco products
vary widely by brand and by country,
based on a number of factors including moisture and pH
levels of the product, how it's manufactured,
and storage practices.
Once in the bloodstream, nicotine
travels through the arterial circulation towards the brain.
It readily penetrates the blood-brain barrier,
allowing the brain to be exposed to nicotine.
If inhaling, it takes about 10 to 20 seconds for nicotine
to reach the brain.
In contrast, oral nicotine products
such as smokeless tobacco result in a more gradual rate
of nicotine absorption and more sustained nicotine levels.
With any smokeless tobacco product,
the amount of nicotine absorbed will depend
on the amount of product used.
Most of the nicotine in the blood
is metabolized to cotinine and other inactive compounds
in the liver, and then excreted by the kidneys.
Nicotine also accumulates in breast milk and amniotic fluid,
and can be detected in the blood and urine of nursing infants
whose mothers use tobacco.
The half life of nicotine is around two hours.
Nicotine binds to receptors in the brain
and other body systems such as the cardiovascular system,
gastrointestinal system, and peripheral nervous system.
In the brain, it binds to ligand-gated ion channels
receptors called nicotine acetylcholine receptors.
When nicotine binds to these receptors,
it opens the channel to allow sodium and calcium
into the neurons, which causes reactions within the neurons
and allows them to release various neurotransmitters
into the brain.
One of these neurotransmitters, dopamine,
causes the experience of pleasure
through the dopamine reward pathway, which contributes
to tobacco addiction.
This pathway is located in the middle of the brain
where nicotine binds to neurons at the ventral tegmental area,
causing a release of dopamine at the nucleus accumbens
and prefrontal cortex.
While being responsible for the sensation of pleasure,
dopamine also suppresses appetite.
Quitting tobacco can cause physical and psychological
withdrawal symptoms.
Most symptoms occur within the first one to two days,
peak within the first week, and subside
within two to four weeks.
These symptoms can be alleviated by smoking or using
smokeless tobacco products, which
is a major reason why people attempting to quit relapse.
Symptoms can include cravings, increased appetite,
weight gain, irritability, anxiety,
difficulty concentrating, depressed mood, and insomnia.
A person's behavioral patterns associated
with using tobacco throughout the day
also reinforce addiction.
For example, behavioral patterns include the habit of smoking
when waking in the morning, eating, finishing a meal,
drinking coffee or other beverages,
and watching television.
These patterns can complicate a user's quit attempt
and can trigger strong urges to use tobacco.
For a daily tobacco smoker, their first cigarette
of the day causes the concentration
of nicotine in their blood to spike to a level that
signals pleasure in the brain.
After a smoker is finished with their cigarette,
the level of nicotine in their blood
begins to decline until the next cigarette is smoked.
Often, that next cigarette is smoked
when the level of nicotine in their blood
falls below a certain threshold, causing the smoker
to feel symptoms of nicotine withdrawal, which
include cravings.
As a daily smoker smokes throughout the day,
the level of nicotine required to maintain their usual level
of pleasure increases, meaning that it takes more nicotine
to get the same effects.
This phenomenon is called tolerance.
Cessation of smoking overnight resensitizes the body
to the effects of nicotine.
Most smokers who are dependent on cigarettes
tend to consume 10 to 40 milligrams of nicotine per day
to achieve the desired effects of smoking.
These effects involve maintaining
pleasure and arousal, mood control during times
of stress and anxiety, and prevention
of withdrawal symptoms.
In closing, tobacco use involves a physiological addiction
to nicotine, as well as patterns of behavior.
Both are critical to address when
treating a patient for tobacco dependence.
It's important to understand the interaction
of external and internal factors that contribute to tobacco use.
The next video will discuss the health consequences
of tobacco use and the benefits of quitting in more detail.