Main indications for respiratory agents
Clinical pharmacology distinguishes several groups of pathological conditions that require the administration of drugs affecting the respiratory system. The choice of a specific drug class strictly depends on the nature of the developed pathology:
- For respiratory depression, respiratory stimulants proper are used, as well as specific antagonists of depressant agents.
- If the patient is troubled by a cough, physicians prescribe expectorants (to improve sputum clearance) and antitussives.
- In bronchial asthma, therapy is based on the use of bronchodilators, as well as anti-inflammatory and antiallergic drugs.
- In the event of respiratory failure and distress syndrome, the primary indication is the administration of surfactant preparations.
Classification of respiratory stimulants
Drugs that restore depressed breathing are classified into three main groups. This pharmacological division is based on their mechanism of action on nervous system structures:
- Central action. This group includes bemegride (Bemegridum) and caffeine (Coffeinum). Pharmacologically, they are analeptics.
- Reflex action. The main representatives are lobeline (Lobelinum) and cytisine (Cytisinum). According to their group affiliation, they are nicotinic receptor agonists.
- Mixed mechanism of action. This category includes nikethamide (Nikethamidum), which is also widely known in clinical practice under the trade name Cordiamine.
Pharmacology of analeptics (central and mixed action)
Drugs such as nikethamide, bemegride, and caffeine provide direct stimulation of the respiratory center. Their key pharmacodynamic effect is that they are able to effectively reduce the depressing influence exerted on the respiratory center by hypnotics and anesthetics.
Main indications for use:
- Mild poisoning with hypnotic drugs or narcotic analgesics.
- Postoperative period (drugs are administered for rapid recovery of adequate breathing after general anesthesia).
The route of administration for these medicines is exclusively parenteral (intravenous or intramuscular).
Important aspect: contraindications and limitations Analeptics are strictly contraindicated in severe poisoning. The pathogenesis of this complication is rooted in the following physiological mechanism: in severe nervous system depression, breathing is not restored under the influence of the drugs. However, the stimulation of neurons leads to a sharp increase in the brain's demand for oxygen. Under conditions of inadequate breathing, this only exacerbates hypoxia and significantly worsens the prognosis for the patient.
Features of reflex-acting stimulants
The drugs lobeline and cytisine work via a completely different pharmacological principle. The localization of their main action is the sinocarotid zone, specifically the carotid bodies.
The mechanism of action unfolds in three consecutive stages:
- Activation of nicotinic acetylcholine receptors located in the carotid bodies occurs.
- This causes a sharp increase in afferent impulses, which are directed via nerve fibers to the medulla oblongata.
- As a result, secondary (indirect) excitation of the respiratory center occurs.
Efficacy profile: Based on the strict logic of their mechanism of action, these drugs have clear limitations. They will be completely ineffective in two clinical situations: if the patient's reflex arc is physically disrupted, or if the respiratory center is profoundly depressed and incapable of adequately responding to incoming afferent impulses.
Briefly: answers to topical questions
Which specific drugs act as antagonists in respiratory depression?
Specific antagonists in drug-induced respiratory depression include antidotes to opioid and benzodiazepine receptors. The following drugs are used in clinical practice:
- Naloxone — administered intravenously, acts for up to 1 hour, displaces opioids from their binding sites with the respiratory center.
- Naltrexone — administered orally, duration of action is up to 36 hours.
- Flumazenil — administered via intravenous drip, is a competitive antagonist of benzodiazepine receptors, effective in overdoses of classical benzodiazepines and Z-drugs.
What side effects are characteristic of analeptics in overdose?
Analeptic overdose leads to dyspeptic and neurological disorders, as well as more severe complications from the central nervous system. The following side effects are characteristic of this group of respiratory stimulants:
- Dyspeptic disorders — manifest as nausea and vomiting.
- Neurological disorders — accompanied by muscle twitching.
- Severe complications — include the development of seizure activity (convulsions).
Which pharmacological groups of drugs are used to treat bronchial asthma?
Bronchodilators, anti-inflammatory, and antiallergic drugs are used to treat bronchial asthma. The main pharmacological groups include:
- Bronchodilators — M-anticholinergics, beta-2 agonists, and myotropic agents (phosphodiesterase inhibitors) for relieving bronchospasm.
- Glucocorticoid drugs — agents for basic anti-inflammatory therapy (including inhaled forms).
- Mast cell stabilizers — cromones used exclusively for the prevention of attacks.
- Leukotriene receptor antagonists — antileukotriene drugs for baseline therapy.
- Genetically engineered biological products — used as an adjunct to baseline therapy in severe disease.
For quick memorization of the classification, use the mnemonic based on initial letters: Central — Bemegride, Caffeine (CBC). Reflex — Lobeline, Cytisine (RLC). Mixed — Nikethamide (MN).
Class and exam questions
Why are analeptics deadly in severe sleeping pill poisoning?
In profound depression, they cannot trigger spontaneous breathing, yet they force neurons to consume more oxygen. This inevitably leads to severe cerebral hypoxia.
To which pharmacological group do lobeline and cytisine belong?
According to their classification, they are nicotinic receptor agonists. They stimulate respiration not directly, but reflexively by acting on the receptors of the carotid bodies.
In which cases do reflex-acting drugs fail to work?
They will have no effect if the patient's reflex arc is damaged or if the respiratory center is in a state of depression so profound that it does not perceive impulses.
What else to study on this topic
- Antagonists of respiratory depressants (specific antidotes and principles of their administration).
- Pharmacology of expectorants and antitussives.
- Bronchodilators and anti-inflammatory agents in the combination therapy of bronchial asthma.
- Surfactant preparations in respiratory failure and distress syndrome.
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