Nicotine
Nicotine is the active ingredient in tobacco.
*JUST FOR INFORMATION* Nicotine remains important because it is second only to caffeine as the most widely used CNS stimulant, and it is second only to alcohol as the most abused drug. In combination with the tars and carbon monoxide found in cigarette smoke, nicotine represents a serious risk factor for lung and cardiovascular disease, various cancers, and other illnesses. Dependency on the drug is not easily overcome. *NOT IMPORTANT*
Mechanism of Action
1. In low doses, nicotine causes ganglionic stimulation by depolarization.
2. At high doses, nicotine causes ganglionic blockade.
Nicotine receptors exist at a number of sites in the CNS, which participate in the stimulant attributes of the drug.
Actions
CNS
Nicotine is highly lipid soluble and readily crosses the blood–brain barrier. Cigarette smoking or administration of low doses of nicotine may cause
• euphoria
• arousal
• relaxation
• improves attention
• learning
• problem solving
• reaction time
High doses of nicotine result in central respiratory paralysis and severe hypotension caused by medullary paralysis
Nicotine is also an appetite suppressant
Peripheral Effects
• At Low Dose
o Due to Stimulation of Sympathetic ganglia and Adrenal Medulla:
o Increase Blood Pressure
o Heart Rate
o Causes Vasoconstriction (affect angina patient)
o Due to Stimulation of Parasympathetic Ganglia
o Increase motor activity of bowel
• At High Dose
o Blood Pressure decreases
o Cessation of GIT and Bladder Musculature (due to blockade of Parasympathetic ganglia)
Pharmacokinetics
➢ Because nicotine is highly lipid soluble, absorption readily occurs via the
o Oral mucosa
o Lungs
o GI mucosa
o Skin
➢ Nicotine crosses the placental membrane and is secreted in the breast milk.
➢ By inhaling tobacco smoke, the average smoker takes in 1 to 2 mg of nicotine per cigarette.
➢ The acute lethal dose is 60 mg.
➢ More than 90% of the nicotine inhaled in smoke is absorbed.
➢ Clearance of nicotine involves metabolism in the lung and the liver and urinary excretion.
➢ Tolerance to the toxic effects of nicotine develops rapidly, often within days.
Adverse Effects
• Irritability
• Tremors
• Cramps
• Diarrhoea
• Increase Heart Rate
• Increase Blood Pressure
• Increase metabolism of many drugs
Withdrawal Syndrome
Severe Physical Dependence can occur due to nicotine, characterized by
• Irritability
• Anxiety
• Restlessness
• Difficulty concentrating
• Headaches
• Insomnia
• Effect on Appetite
• GI upset often occurs
The transdermal patch and chewing gum containing nicotine have been shown to reduce nicotine withdrawal symptoms and to help smokers stop smoking.
Other forms of nicotine replacement used for smoking cessation include the inhaler, nasal spray, and lozenges.
Bupropion, an antidepressant can reduce the craving for cigarettes.
Therapeutic Uses
Although this drug is not currently used therapeutically (except in smoking cessation therapy).
