Chemical nature and mechanism of action
By its chemical structure, the drug is N-acetyl-L-cysteine. In medical practice, it is known under such trade names as ACC, Mucosolvin, and Mucobene.
The main pharmacological property of the drug is mucolytic action. It is implemented in two ways:
- Direct effect on sputum structure. The molecule contains free sulfhydryl groups (-SH). They are able to cleave disulfide bonds in the proteoglycans of the bronchial secretion. As a result, depolymerization of macromolecules occurs, leading to a sharp decrease in the viscosity and adhesiveness of sputum.
- Additional effects. The drug stimulates the secretion of mucous cells, increasing the total volume of secretion. In addition, it causes lysis of fibrin, which is especially important in the presence of purulent or fibrinous sputum.
Systemic effects: antioxidant and antidote
In addition to its effect on the respiratory tract, the drug has important systemic properties:
- Antioxidant and anti-inflammatory action. The compound actively suppresses the formation of free radicals. Due to this mechanism, the severity of the inflammatory reaction directly in the bronchial tree is significantly reduced.
- Detoxifying action. The substance stimulates the synthesis of glutathione, the most important factor in the body's endogenous detoxification. That is why it is used in toxicology as an antidote for paracetamol (acetaminophen) overdose, acting as a glutathione donor for the prevention of severe hepatotoxicity.
Pharmacokinetics and routes of administration
The drug is available in various dosage forms, which determines the variety of its routes of administration:
- Enteral: orally in the form of effervescent tablets or granules.
- Parenteral: intramuscularly and intravenously.
- Topical and inhalation: in the form of inhalations or intratracheal instillation.
When taken orally, absorption is rapid and complete. However, the final bioavailability remains low (does not exceed 10%). This is due to the pronounced "first-pass" effect through the liver, where deacetylation of the molecule to ordinary cysteine occurs.
Indications, contraindications, and safety
Main indications for use:
- Inflammatory respiratory diseases (chronic bronchitis, tracheobronchitis, pneumonia).
- Bronchial asthma and chronic obstructive pulmonary disease (COPD).
- Paracetamol poisoning.
Safety profile and side effects: Dyspeptic disorders (nausea and vomiting), allergic reactions in the form of urticaria, as well as tinnitus may occur during therapy.
Absolute contraindications:
- Peptic ulcer of the stomach and duodenum.
- Predisposition to pulmonary hemorrhage.
- Liver and kidney diseases, adrenal dysfunction.
- Periods of pregnancy and lactation.
Drug interactions
When prescribing, it is important to consider pharmaceutical and pharmacological compatibility:
- Pharmaceutical incompatibility. It is strictly forbidden to mix the drug in the same syringe or solution with antibiotics and proteolytic enzymes, as this leads to their inactivation. Contact with rubber and metals (copper, iron) causes the formation of sulfides and the appearance of a specific odor.
- Pharmacokinetic interaction. The agent reduces the absorption of a number of antibiotics (penicillins, cephalosporins, tetracyclines). An interval of at least two hours must be observed between their administration.
- Pharmacodynamic interaction. The drug is able to enhance the vasodilating effect of nitroglycerin.
Briefly: answers to topical questions
What is the dosing regimen for acetylcysteine in acute paracetamol poisoning?
For drug-induced liver injury, including paracetamol overdose, a stepped intravenous infusion scheme of the antidote is used.
The dosing protocol includes the following stages:
- Loading dose — 150 mg/kg/h (administered over 1 hour).
- Intermediate dose — 12.5 mg/kg/h (administered over 4 hours).
- Maintenance dose — 6.25 mg/kg (administered over 67 hours).
This administration regimen significantly improves patient survival without liver transplantation and reduces overall hospitalization times.
What metabolites are formed during the biotransformation of acetylcysteine in the liver?
When taken orally, acetylcysteine undergoes deacetylation in the liver to form cysteine. The bioavailability of the drug is low, accounting for no more than 10% due to the hepatic "first-pass" effect.
To easily remember the mechanism of action, imagine "SH-scissors": the free sulfhydryl (-SH) groups of acetylcysteine literally "cut" the disulfide bridges in thick sputum, turning it into a liquid.
Class and exam questions
Why does acetylcysteine save lives in paracetamol poisoning?
It acts as a donor for glutathione synthesis. Glutathione is essential for the endogenous detoxification of paracetamol metabolites, preventing severe liver damage (hepatotoxicity).
Can you wash down antibiotics with a solution of this mucolytic?
No, it significantly reduces the absorption of penicillins, cephalosporins, and tetracyclines. There must be an interval of at least two hours between taking these drugs.
Why does the drug solution sometimes acquire an unpleasant odor?
When the solution comes into contact with metals (e.g., iron or copper) or rubber, a chemical reaction occurs with the formation of sulfides, which produce the characteristic odor.
What else to study on this topic
- Biochemical bases of glutathione synthesis and the role of cysteine
- Mechanism of paracetamol (acetaminophen) hepatotoxicity
- The hepatic "first-pass" effect using mucolytics as an example
- Features of the use of mucolytics in purulent and fibrinous sputum
- Pathogenesis of bronchospasm during intravenous drug administration
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