General characteristics and pharmacological effects
The pharmacological group of psychostimulants combines compounds that affect the central nervous system. Their key action consists in stimulating brain functions and facilitating interneuronal transmission.
Main clinical and physiological effects of administration:
- Increased mental performance and concentration.
- Increased reflex speed and physical endurance.
- Reduced feeling of fatigue and decreased need for sleep.
- Appetite suppression (anorexigenic effect).
An important property of these substances is dose-dependency: in high doses, they can exhibit analeptic (awakening) action, but this also provokes anxiety, nervousness, and physical tension.
Classification of psychostimulants
The grouping of drugs is based on their chemical structure and the characteristics of their mechanism of action. Modern pharmacology distinguishes three main groups:
- Phenylalkylamine derivatives — a prominent representative is amphetamine (phenamine). The drug is a racemic mixture of isomers, with the dextrorotatory isomer carrying the main activity.
- Sydnonimine derivatives — these include mesocarb (sydnocarb).
- Methylxanthine derivatives — a classic example is caffeine.
Mechanism of action and effects on the central nervous system
The action of phenylalkylamine derivatives at the neurochemical level is associated with their effect on catecholamines. The drugs cause active release of norepinephrine and dopamine from presynaptic terminals, block their neuronal reuptake, and also possess inhibitory activity against the enzyme monoamine oxidase (MAO).
At the organism level, this is manifested as central and peripheral effects:
- Psychostimulating action: euphoria, elimination of fatigue, increased performance. Notably, at high working speeds, accuracy may decrease.
- Autonomic manifestations: increased blood pressure, tachycardia, and increased myocardial oxygen demand due to adrenoceptor stimulation.
- Age characteristics: psychostimulation is observed in adults, whereas the same drugs may cause a sedative (calming) effect in children.
Energy balance and body characteristics
The use of psychostimulants is accompanied by a serious mobilization of internal forces. Regular administration of the drugs leads to rapid depletion of the body's energy resources, as they expend existing reserves rather than creating new energy. In addition, constant stimulation of the hunger center in the hypothalamus leads to a persistent decrease in the need for food.
Briefly: answers to topical questions
Which drugs belong to the methylxanthine derivative group?
The methylxanthine derivative group includes caffeine, theobromine, theophylline, and aminophylline.
- Caffeine — an alkaloid with the most pronounced effect on the central nervous system; blocks purine receptors and inhibits phosphodiesterase.
- Theobromine — a plant-derived alkaloid.
- Theophylline — an alkaloid that blocks purine receptors.
- Aminophylline — a drug with a cholecystospasmolytic effect (reduces the tone of the smooth muscles of the bile ducts).
What side effects are characteristic of psychostimulants when used in high doses and for prolonged periods?
When psychostimulants are used in high doses and during prolonged administration, anxiety, nervousness, physical tension, psychotic disorders, fatigue, depletion of the body's energy resources, insomnia, and dependence are possible.
- At high doses: anxiety, nervousness, and physical tension occur. In case of overdose, tremor and convergence insufficiency are possible. With dose escalation, the development of hallucinatory-paranoid psychosis is possible, including persecutory delusions, auditory and tactile hallucinations.
- With prolonged administration: rapid fatigue and depletion of the body's energy resources, insomnia, tolerance, and a high risk of pathological craving are possible. For caffeine, sources indicate the possibility of developing tolerance and drug dependence (theism).
What are the main medical indications for prescribing psychostimulants?
The main medical indications for prescribing psychostimulants are conditions accompanied by decreased activity and specific syndromes.
- Psychiatry and neurology: mild negative, depressive, and apathetic-abulic disorders in schizophrenia, subdepressive states.
- Asthenia: general weakness and asthenic states.
- Sleep disorders: hypersomnia (narcolepsy).
- Pediatrics: attention deficit hyperactivity disorder (ADHD).
- Therapy correction: elimination of side effects of sedatives and anticonvulsants.
- Other: obesity (occasionally, due to the anorexigenic effect).
What absolute and relative contraindications exist for the use of psychostimulants?
Sources do not provide a clear division of contraindications for psychostimulants into absolute and relative. The following contraindications are indicated for caffeine:
- pronounced arterial hypertension;
- atherosclerosis;
- glaucoma;
- insomnia.
How does the mechanism of action and spectrum of effects of mesocarb (sydnocarb) differ from amphetamine?
Mesocarb differs from amphetamine by a milder action, the absence of initial euphoria, and a lesser effect on autonomic functions.
| Characteristic | Mesocarb (Sydnocarb) | Amphetamine |
|---|---|---|
| Mechanism of action | Displaces norepinephrine from presynaptic vesicles into the synaptic cleft, activating noradrenergic transmission | Causes the release of catecholamines from presynaptic terminals; blocks the neuronal reuptake of norepinephrine and dopamine and inhibits MAO |
| Onset of effect | Gradual, "milder", without initial euphoria | Characterized by a psychostimulating action and the development of euphoria |
| Energy balance | Does not cause subsequent depletion of the body's energy resources | Regular intake leads to rapid depletion of the body's energy resources |
| Autonomic effects | Peripheral sympathomimetic action is negligible; less likely to provoke an increase in blood pressure | Increases blood pressure and causes tachycardia |
| Dependence | Develops significantly slower than with phenylalkylamine derivatives | Psychostimulants are characterized by a high risk of drug addiction |
Psychostimulants boost tone and speed up reflexes, but remember the rule: they work the body to exhaustion, consuming its internal resources.
Class and exam questions
What are the main neurotransmitters targeted by amphetamine?
The main target neurotransmitters are norepinephrine and dopamine. The drug stimulates their release from presynaptic terminals and blocks reuptake.
What are the age-related differences in the action of psychostimulants?
In adults, these substances cause a pronounced psychostimulatory effect, whereas in children, a paradoxical sedative (calming) action is observed.
How do psychostimulants affect the cardiovascular system?
They cause an increase in blood pressure, tachycardia, and increase myocardial oxygen demand due to enhanced norepinephrine release and adrenoceptor stimulation.
What else to study on this topic
- Pharmacology of sydnnoneimine derivatives (mesocarb)
- Features of the action of methylxanthine derivatives (caffeine)
- Effect of amphetamine on the hypothalamus and hunger center
- Development of tolerance and energy resource depletion with psychostimulant use
- Comparative analysis of central and peripheral effects of sympathomimetics
Master the entire topic in the «Pharmacology» course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Psychostimulants" and 5,304 more subject pages
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 116 video lessons on the subject
Other topics in the section "Agents Used in Psychiatry and Neurology"
Free video lessons: pharmacologyShort lessons with study notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.