Usage
Acetylcysteine is prescribed for the following medical conditions:
- Mucolytic agent: Used to thin and loosen mucus in the airways, making it easier to cough up. This is beneficial in conditions such as chronic bronchitis, cystic fibrosis, pneumonia, and other respiratory illnesses where thick mucus is a problem. It is also used for diagnostic bronchograms to enhance visibility.
- Acetaminophen (paracetamol) overdose antidote: It helps prevent or reduce liver damage caused by an overdose of acetaminophen.
- Meconium ileus: Given rectally to break down thick meconium in the intestines of newborns.
Pharmacological Classification: Mucolytic agent and antidote.
Mechanism of Action (brief): Acetylcysteine works by breaking disulfide bonds in mucus, reducing its viscosity. In acetaminophen overdose, it replenishes glutathione, a substance that helps detoxify the harmful byproduct of acetaminophen metabolism.
Alternate Names
- N-acetyl-L-cysteine
- N-acetylcysteine (NAC)
Brand Names:
Numerous brand names exist depending upon the region.
How It Works
Pharmacodynamics: Acetylcysteine reduces the viscosity of mucus by disrupting disulfide bonds in mucoproteins. In acetaminophen overdose, it acts as a precursor for glutathione synthesis, thereby enhancing the liver’s capacity to detoxify the toxic metabolite of acetaminophen (N-acetyl-p-benzoquinone imine or NAPQI).
Pharmacokinetics:
- Absorption: Well-absorbed orally, though bioavailability is low due to first-pass metabolism.
- Metabolism: Extensively metabolized in the liver.
- Elimination: Primarily renal excretion.
Mode of Action: Acetylcysteine’s mucolytic action is through the free sulfhydryl group of the molecule, which opens disulfide bonds in mucus glycoproteins, decreasing viscosity. In acetaminophen toxicity, it acts as a substrate for glutathione synthesis and also directly conjugates with NAPQI.
Receptor Binding/Enzyme Inhibition/Neurotransmitter Modulation: Acetylcysteine does not directly bind to receptors, inhibit enzymes (in its mucolytic role), or modulate neurotransmitters. Its action is primarily chemical (disulfide bond breaking).
Dosage
Standard Dosage
Adults:
- Mucolytic:
- Oral: 200-600 mg, two to three times daily.
- Inhalation: 1-10 mL of a 20% solution (or 2-20 mL of a 10% solution) via nebulizer every 2-6 hours.
- Acetaminophen overdose:
- Consult with a poison control center or refer to the specific protocol for intravenous administration. Generally, a loading dose followed by maintenance doses is given intravenously.
Children:
- Mucolytic: Consult a healthcare professional for appropriate dosing based on the child’s age and weight.
- Acetaminophen overdose: Consult with a poison control center or refer to a specialized pediatric protocol. Intravenous administration is typical.
Special Cases:
- Elderly Patients: Dosage adjustments may be necessary based on kidney function.
- Patients with Renal Impairment: Dose reduction may be required.
- Patients with Hepatic Dysfunction: While the half-life may be increased, dose adjustments are not specifically recommended in the literature.
- Patients with Comorbid Conditions: Consider individual patient factors.
Clinical Use Cases
- Intubation/Surgical Procedures/Mechanical Ventilation/ICU Use: Dosage varies widely and should be based on the specific clinical needs. Nebulization is the common route.
- Emergency Situations (Acetaminophen overdose): Intravenous administration based on a specific protocol is essential.
Dosage Adjustments
Adjustments may be required based on renal function, hepatic function, patient response, and other individual factors.
Side Effects
Common Side Effects
- Nausea
- Vomiting
- Stomatitis (oral administration)
- Rhinorrhea
- Bronchospasm (inhalation)
Rare but Serious Side Effects
- Angioedema
- Anaphylaxis
- Hepatic injury (at high doses)
Long-Term Effects
Generally, acetylcysteine is well-tolerated, and long-term effects are uncommon.
Adverse Drug Reactions (ADR)
Severe allergic reactions like angioedema and anaphylaxis require immediate medical attention.
Contraindications
- Hypersensitivity to acetylcysteine.
Drug Interactions
- Nitroglycerin: Concurrent use may potentiate the hypotensive effects of nitroglycerin.
- Activated charcoal: May reduce the effectiveness of oral acetylcysteine in acetaminophen overdose.
Pregnancy and Breastfeeding
Acetylcysteine is generally considered safe during pregnancy. While it is excreted in breast milk, it is considered compatible with breastfeeding, though some sources suggest discarding breast milk for a period after administration.
Drug Profile Summary
- Mechanism of Action: Mucolytic via disulfide bond breaking; antidote in acetaminophen overdose by replenishing glutathione.
- Side Effects: Nausea, vomiting, stomatitis, rhinorrhea, bronchospasm (rarely, severe allergic reactions).
- Contraindications: Hypersensitivity.
- Drug Interactions: Nitroglycerin, activated charcoal.
- Pregnancy & Breastfeeding: Generally safe.
- Dosage: Varies depending on indication and route of administration. Refer to specific sections above.
- Monitoring Parameters: Liver function tests (in acetaminophen overdose), respiratory status (inhalation).
Popular Combinations
Acetylcysteine is often used in combination with bronchodilators in respiratory conditions to improve airway clearance.
Precautions
- Close monitoring of patients with asthma for bronchospasm.
- Caution in patients with a history of gastrointestinal bleeding (oral administration).
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Acetylcysteine?
A: The dosage varies depending on the indication, route of administration, patient’s age, and other individual factors. See detailed dosage guidelines above.
Q2: How should Acetylcysteine be administered for acetaminophen overdose?
A: Intravenously, following a specific protocol based on the time since ingestion and the patient’s condition. Consult a poison control center for guidance.
Q3: What are the common side effects of Acetylcysteine inhalation?
A: Nausea, vomiting, stomatitis, rhinorrhea, and bronchospasm.
Q4: Can Acetylcysteine be used during pregnancy?
A: Yes, it’s generally considered safe.
Q5: Are there any significant drug interactions with Acetylcysteine?
A: Nitroglycerin and activated charcoal are among the noted interactions.
Q6: How does Acetylcysteine work as a mucolytic?
A: It breaks disulfide bonds in mucus, decreasing its viscosity.
Q7: What is the role of Acetylcysteine in treating meconium ileus?
A: Administered rectally, it helps dissolve the thick meconium obstruction.
Q8: How should Acetylcysteine solution be prepared for nebulization?
A: Refer to the manufacturer’s instructions for the specific product. Standard concentrations are 10% and 20%.
Q9: What is the duration of treatment with Acetylcysteine for respiratory conditions?
A: It depends on the nature and severity of the condition. Consult a healthcare professional for guidance.
