7. ANALEPTICS

Analeptics are common CNS stimulants. They either enhance the excitation process, or inhibit the braking mechanisms. Analeptics operate at almost all levels of the CNS. So, some substances have a predominant effect on the centers of the medulla oblongata (corazol, bemegride, cordiamine), others on the spinal cord (strychnine). In caffeine, which can also be seen in the analeptic group, a psychostimulant effect prevails, due to its effect on the cerebral cortex.

An increase in the dose of analeptics leads to the generalization of excitation processes, accompanied by an increase in reflex excitability. In toxic doses, analeptics cause convulsions, which is why they are sometimes called convulsive poisons. There are analeptics, stimulating and convulsive effects which are caused by inhibition of the inhibitory processes. Thus, picrotoxin blocks the chlorine channels associated with GABA receptors. In this way, the postsynaptic inhibitory effect of GABA is eliminated. Strychnine also weakens the postsynaptic inhibition, which mediator is glycine (due to the block of glycine receptors). The inhibitory effect of GABA strychnine is not affected.

The most common analeptics in practice:

Alkylated acid amides

Cordiamin (niketamide, coramin)

Bicyclic ketones

Camphor

Glutarimides

Bemegride (megimide)

Of greatest interest is the stimulatory effect of analeptics on the vital centers of the medulla oblongata - the respiratory and vasomotor, which is especially when they are inhibited.

Analeptics increase the excitability of the respiratory center: its sensitivity to humoral stimuli (CO ₂ ) and nerve stimuli increases. A number of drugs (bemegride, camphor) have a direct stimulating effect on the center of respiration.

Analeptics stimulate the vasomotor center, leading to increased blood pressure. Blood circulation is generally improving. This is manifested mainly in low blood pressure. They do not have a direct effect on the heart, with the exception of camphor and caffeine.

It should be borne in mind that the range between the doses of analeptics (bemegride, cordiamine, camphor) required to stimulate the respiratory and vasomotor centers, and the doses in which they cause seizures is insignificant.

For analeptic activity, drugs can be placed in the following row: bemegride> cordiamine> camphor.

Analeptics are functional antagonists of narcotic-type substances and may contribute to the removal from anesthesia (the so-called "awakening effect" analeptics). However, this effect is observed with the introduction of analeptics in significant doses, in which they can cause seizures. At the same time, CNS stimulants can be used to accelerate the recovery of psychomotor reactions in the post-anesthetic period (analeptic is administered at the "exit" from anesthesia).

For analeptic action, drugs are usually injected parenterally.

Analeptics are used for mild degrees of poisoning with anesthetic agents, narcotic type 1 sleeping pills, ethyl alcohol, and also for external respiratory disorders of a different etiology, for example, asphyxia of the newborn. Cordiamin and camphor are also used in cardiovascular insufficiency, although their effectiveness in this pathology is not universally recognized.

The stimulators of the central nervous system also include corazol, securinine, vinca hydrochloride. A peculiar pharmacodynamics has a respiratory stimulator etyfizol.