Mechanism of Action and Classification
Analeptics restore body function by exciting vital centers in the medulla oblongata. Depending on how the drugs deliver the stimulating signal, they are divided into three main groups:
- Direct action. Directly activate centers in the brain. This group includes pentetrazole and bemegride.
- Reflex action. Excite N-cholinergic receptors located in the carotid body. From there, nerve impulses are reflexively transmitted to the medulla oblongata. Representatives: cytisine and lobeline.
- Mixed mechanism. Combine both stimulation pathways (both direct and reflex). A typical example is nikethamide.
In addition, drugs differ in their safety profile. For example, caffeine has a relatively wide therapeutic index, whereas strychnine has a narrow one, requiring high caution when prescribing it.
Specific Actions of Individual Agents
Different analeptics have specific "targets" in the nervous system, determining their clinical applications:
- Strychnine — predominantly stimulates the spinal cord.
- Caffeine — exerts a greater effect on the cerebral cortex and subcortical structures.
- Sulfocamphocaine — acts selectively, stimulating only the medulla oblongata.
In order of decreasing CNS stimulating potency, the drugs can be arranged as follows:
- Pentetrazole (Corazole)
- Bemegride
- Strychnine
- Caffeine
- Sulfocamphocaine
- Nikethamide (Cordiamin)
- Etimizole (Methylamide ethylimidazole dicarboxylate)
Pharmacological Effects and Indications
The main outcome of analeptic action is enhanced respiration and circulation. Indirectly, they promote the recovery of renal function and accelerate the biotransformation and elimination of toxic substances with narcotic properties from the body.
In clinical practice, analeptics are used for the following conditions:
- Asphyxia in newborns.
- Shock, collapse, and severe hypotension.
- Depression of vital centers of various etiologies.
- As antagonists in cases of general anesthetic and hypnotic overdose.
Important clinical nuance: the best therapeutic effect is achieved not by increasing the dose of a single drug, but through the combination therapy of various analeptics in low doses.
Side Effects and Contraindications
The use of CNS stimulants is always associated with the risk of adverse reactions. The main side effects of analeptics include:
- Dyspeptic symptoms: nausea and vomiting.
- Neurological disorders: involuntary muscle twitching.
- Severe complications: overdose causes a pronounced convulsive syndrome (seizures).
Bemegride requires special attention. Although analeptics are generally used as hypnotic antagonists, bemegride is contraindicated in severe hypnotic poisonings. This is due to the underlying pathophysiology: the drug sharply increases oxygen consumption by brain neurons. If hypoxia, characteristic of severe poisoning, is not corrected, such metabolic stimulation will only exacerbate nerve cell damage.
Role in Respiratory Therapy
In the general classification of pharmacological agents affecting the respiratory system, there are five main categories. Analeptics act as respiratory stimulants.
To understand their place in therapy, it is important to distinguish them from other groups:
- Antitussives — aim to suppress the cough reflex.
- Expectorants — improve mucus clearance from the airways.
- Bronchodilators — widen the bronchial lumen.
- Surfactant preparations — affect surface tension in the alveoli.