6. PSYCHOSTIMULATORS classification, purpose, side effects

Psychostimulants increase mood, the ability to perceive external stimuli, psychomotor activity. They reduce the feeling of tiredness, increase physical and mental performance (especially with fatigue), temporarily reduce the need for sleep.

By chemical structure belong to the following groups.

Phenylalkylamines

Phenamine

Piperidine derivatives

Pyridrol Meridil

Derivatives of Sidnonimine

Sydnokarb

Methylxanthines

Caffeine

Typical is phenamine (amphetamine sulfate). Similar in structure to adrenaline and norepinephrine. The mechanism of excitatory action of phenamine is explained by its ability to release norepinephrine and dopamine from presynaptic endings. In addition, phenamine, apparently, somewhat reduces the neuronal uptake of norepinephrine and dopamine.

The excitatory effect of phenamine is associated mainly with its stimulating effect on the ascending activating reticular formation of the brain stem. On the EEG, this is manifested by the desynchronization of bioelectric activity. However, it is possible that phenamine excites neurons of the cerebral cortex and directly. In addition, it stimulates the individual formations of the limbic system and inhibits the neostriatum.

Phenamine in small doses has a beneficial effect on the development and realization of conditioned reflexes, and inhibits them in large doses. At the same time, the type of the nervous system is important.

For phenamine is characterized by its effect on the food center, located in the hypothalamus, which leads to the suppression of hunger.

Phenamine has a direct stimulating effect on the center of respiration. In this case, phenamine acts as an analeptic (depressing breathing).

Phenamine acts not only on the central nervous system, but also on peripheral innervation. It has an indirect stimulating effect on the α- and α-adrenoreceptors. Sympathetic and adrenomimetic properties of phenamine are manifested mainly in the increase in blood pressure: adrenaline is 100–150 times lower in activity, but the pressure effect is much longer.

The drug is absorbed well, penetrates the blood-brain barrier. To reduce its plasma concentration by 50%, it takes about 12 hours.

With prolonged use of phenamine cumulates, addictive to it and drug dependence (mental and physical) develop.

Phenamin is used for neurotic subdepression, as well as for narcolepsy and similar conditions accompanied by drowsiness. In addition, sometimes it is used to improve performance with fatigue. The stimulating effect of phenamine is accompanied by a large expenditure of energy resources of the body, so the subsequent full rest for restoring strength is absolutely necessary.

Phenamine is sometimes prescribed as an analeptic in case of poisoning with substances of a narcotic type of action.

In case of overdose, excitement, anxiety, insomnia, tachycardia, and sometimes heart rhythm disturbances are noted. Phenamine is contraindicated in atherosclerosis, hypertension, insomnia, in old age.

Currently, phenamine is rarely used (due to its ability to cause drug dependence).

Similar to phenamine, piperidine derivatives pyridrol (pipradol) and meridyl (methylphenidate hydrochloride, centedrin). The undoubted advantage of pyridrol and meridyl is the absence of unwanted peripheral adrenomimetic effects.

Sydnokarb belongs to the group of sydnonimine. The psychostimulating effect of sydnocarb develops gradually and persists for a long time. Euphoria and motor excitation is not observed. The mechanism is associated with the activation of the noradrenergic system. Sydnocarb lacks a pronounced peripheral sympathomimetic effect. In case of overdose, excitement, anxiety, insomnia, a slight increase in blood pressure are possible. Sydnocarb should not be taken in the evening as it may disturb sleep.

Caffeine (a compound from the group of methylxanthines) also belongs to the group of psychostimulants. It is an alkaloid found in tea leaves, coffee , cocoa , cola, and other plants. Caffeine combines psychostimulant and analeptic properties. Especially pronounced direct excitatory effect on the cerebral cortex. Caffeine stimulates mental activity, increases mental and physical performance, physical activity, shortens the reaction time. After taking it, vigor appears, fatigue, drowsiness are temporarily eliminated or reduced.

The effect on higher nervous activity depends on the dose of caffeine and the type of nervous system. In small doses, caffeine has a stimulating effect, and in large doses it is depressing. For a weak type of nervous system, the excitation effect is achieved by administering small doses of caffeine, whereas a strong type requires significantly larger doses.

Analeptic activity is associated with the effect of caffeine on the centers of the prolonged brain. It has a direct stimulating effect on the respiratory and vasomotor centers (increased and increased breathing). Caffeine excites the centers of the vagus nerves. The drug acts on the spinal cord only in large doses, it enhances the spinal reflexes.

A significant place is occupied by its effect on the cardiovascular system: a direct stimulating effect on the myocardium, while the centers of the vagus nerves are excited, the final effect depends on the predominance of one or another effect. In large doses, caffeine causes tachycardia (ie, its peripheral action prevails), sometimes arrhythmias.

Stimulating the vasomotor center, caffeine increases vascular tone, and with a direct effect on vascular smooth muscle, reduces their tone.

Caffeine has an ambiguous effect on different vascular areas: the coronary vessels dilate, the cerebral vessels somewhat toned. Caffeine has a moderate myotropic antispasmodic effect on other gadal organs (bronchi, bile ducts), stimulating (central and direct) on skeletal muscles.

Blood pressure is difficult to change, as it depends on the cardiotropic and vascular effects of caffeine. Usually, if the initial blood pressure is normal, caffeine does not change or very slightly increases it. If the drug is introduced on the background of hypotension, blood pressure rises (normalizes).

Caffeine increases basal metabolism. The change in metabolism is associated with the accumulation of cAMP.

Under the influence of caffeine, the secretion of the gastric glands increases, and this can be used for diagnostic purposes. The use of caffeine in the pathology of the gastric (gastritis, peptic ulcer, tumors) helps to differentiate functional disorders from organic.

Caffeine increases diuresis to a small extent.

With prolonged use of caffeine develops slightly addictive. Psychic addiction is possible (theism).

Caffeine is used to stimulate mental activity, with fatigue, migraine, hypotension. It is a part of many combined drugs in combination with non-narcotic analgesics (tablets "Citramon", "Piramein", etc.) and ergot alkaloids (tablets "Cofetamine").

Side effects are manifested in the form of nausea, vomiting, anxiety, agitation, insomnia, tachycardia, cardiac arrhythmias.

Caffeine is contraindicated in severe hypertension, atherosclerosis, sleep disorders, glaucoma.