Stimulants are largely opposite to that of depressants, as they increase the activity of the brain and hence the person's state of mental alertness. They are used to prevent excessive drowsiness through the day and so allow greater concentration.
- They help facilitate breathing by causing relaxation of the air passages and are used in the treatment of respiratory infections such as severe bronchitis
- They may reduce appetite and so have been used as part of treatment for obesity
- They may cause palpitation or tremors to occur
- When used in excess, they can cause restlessness, sleeplessness, fits, delusions and hallucinations.
D.5.2 Compare amphetamines and epinephrine (adrenaline)
Adrenaline is a hormone that is released in times of stress and enables the body to cope with sudden demands such as those imposed by pain, shock, fear and cold. It is called the "fight or flight" reaction.
- increase the heart rate and blood pressure
- increase the blood flow to the brain and the muscle
- increase the air flow to the lungs
- increase mental awareness
The amphetamines are called sympathomimetic drugs. In small doses, amphetamines increase mental alertness and physical energy. Side-effects include dilation of the pupils and decreased appetite, as well as possible blurred vision and dizziness. Regular use of these drugs leads to the rapid development of both tolerance and dependence, coupled with serious long-term effects such as severe depression and reduce resistance to infection.
Modification to the amphetamine structure have produced some drugs that are very powerful and dangerously addictive. These include methamphetamine, known as speed and crystal meth, and the drug ecstasy.
D.5.3 Discuss the short- and long-term effects of nicotine consumption
Nicotine is one of the most widespread and abused stimulants. It is obtained from tobacco plants but is also found at low concentrations in tomato, potato, eggplant and green pepper plants. Usually it is taken in by inhalation of smoke from cigarette, cigars and pipe tobacco, but it can also be taken by chewing.
Short-term effects
- Increases concentration
- Relieves tension and boredom
- Helps to counter fatigue
- Increases heart rate and blood pressure
- Decreases urine output
Long-term effects
- High blood pressure
- Increases risk of heart disease including angina
- Coronary thrombosis
- Increases the level of fatty acids in the blood which can lead to atherosclerosis and stroke
- Over-stimulation of stomach acids which can lead to increased risk of peptic ulcers
D.5.4 Describe the effects of caffeine and compare its structure with that of nicotine
Caffeine acts as a respirator stimulant increasing the rate of energy release within cells. It also intensifies and prolongs the effects of adrenaline. As with other drugs, higher consumption may lead to some negative effects.
Consumption of caffeine in small amounts
- Enhancement of mental energy alertness and ability to concentrate
- Acts as a diuretic, increasing volume of urine; can cause dehydration
Consumption of caffeine in large amounts
- Can cause anxiety, irritability and insomnia
- Can cause dependence; side-effects on withdrawal include headaches and nausea
In general, an intake of more than four cups of coffee per day may be considered non-beneficial. Pregnant woman are advised to limit their caffeine intake
Like, nicotine, caffeine contains heterocyclic rings (containing both carbon and nitrogen) and a tertiary amine group. In addition, caffeine contains two amide groups.
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