Amphetamines are indirectly acting. They act more powerfully on the CNS because in addition to noradrenaline, other biogenic amines are also produced including dopamine and serotonin.
In the periphery, effects are produced by noradreanline.
Amphetamines produce euphoria, alertness, increase the ability of a person to concentrate and reduce sleepiness because of action on cerebral cortex as well as the ascending reticular activating system. The effects are much more potent than that of ephedrine.
Action on the lateral hypothalamus (feeding center) suppresses the appetite producing anorexia. In the older days, amphetamines were used for obesity. Certain variants are still used.
Amphetamines have a mild analgesic action, when combined with morphine, its activity is enhanced.
Amphetamines stimulate the respiratory center. Produce increase in respiratory rate and depth because of central effect.
- In periphery noradrenaline increases the contractility.
- Increase in heart rate
- Increase in blood pressure
- Sometimes reflex bradycardia is also seen
1. Depression –not indicated any more (selective serotonin reuptake inhibitors available now)
2. ADHD (Attention Deficit Hyperactivity Disorder)
This is a disorder in which the child cannot stay still and is hyperkinetic. Attention span is shorter and performance is not up to the mark. If diagnosed earlier, amphetamines may be used to improve the attention and performance (methyl phenedate and atmoxiline also used). This disease is not confined to childhood only.
Increased sleepiness especially in environment not suitable for sleep. Amphetamines might be given
Phenmetrazine, sibuteramine (Reductil) suppress appetite.
It is abused by athletes for performance enhancement.
Insomnia, restlessness and in toxic doses convulsions
Once the levels of drug in blood fall, fatigue sets in and the person sleeps for a little longer than usual.
Tachycardia, palpitations, hypertension, has ability to produce tolerance and addictive potential.