Acetylcysteine is a prescription medication that helps thin and loosen mucus in the lungs, making it easier to clear through coughing or suction. It is often used as adjuvant therapy for lung conditions with thick or sticky mucus, such as bronchitis, pneumonia, or cystic fibrosis.

In hospitals, acetylcysteine is also used as an antidote to prevent or lessen liver injury caused by acetaminophen overdose. It works by restoring levels of glutathione, a natural antioxidant that protects liver cells from damage.

Treatment with acetylcysteine may involve inhalation therapy for mucus clearance or intravenous infusion for acetaminophen toxicity. A doctor will determine the best dosage and duration, and medical attention is essential if symptoms such as difficulty breathing, chest tightness, or allergic reactions occur.

Common uses

Acetylcysteine may be prescribed as adjuvant therapy to help remove thick or sticky mucus from the airways in conditions such as:

Acute or chronic bronchitis
Emphysema
Pneumonia
Cystic fibrosis
Tracheostomy care or post-surgical mucus obstruction
Diagnostic bronchial studies requiring mucus clearance

It is also prescribed in hospitals to prevent or reduce liver damage caused by acetaminophen overdose.

Is acetylcysteine an antibiotic?

Acetylcysteine is not an antibiotic. It is classified as a mucolytic, which means it helps break down thick, sticky mucus in the airways, making it easier to remove through coughing or suction.

Recommended dosage

Acetylcysteine must be administered exactly as prescribed by the doctor. Dosing, frequency, and treatment duration depend on the condition being treated and the person’s response to therapy.

1. Inhalation solution (for mucus clearance)

Acetylcysteine inhalation solution is available in 10% (100 mg/mL) and 20% (200 mg/mL) strengths.
The usual adult and pediatric dosage is:

3 to 5 mL of the 20% solution, or
6 to 10 mL of the 10% solution

administered by nebulization 3 to 4 times daily, or as often as every 2 to 6 hours, depending on medical advice.
Treatment continues until the mucus is adequately cleared or symptoms improve. During use, an increase in loosened secretions may occur, and airway suction may be needed if coughing is insufficient.

2. Intravenous (IV) infusion for acetaminophen overdose

For suspected or confirmed acetaminophen overdose, acetylcysteine is given intravenously in the hospital. The standard U.S. regimen (21-hour protocol) is:

Loading dose: 150 mg/kg over 1 hour
Second dose: 50 mg/kg over 4 hours
Third dose: 100 mg/kg over 16 hours

Treatment timing and duration are determined by the healthcare team based on blood acetaminophen levels, liver function tests, and clinical response. An oral regimen may be used in limited cases when IV access is not available.

Possible side effects

The most common side effects of acetylcysteine include nausea, vomiting, stomatitis (mouth irritation), runny nose, and chest tightness. Bronchospasm (airway narrowing) can occur with inhalation, especially in people with asthma or reactive airway disease. Rarely, hemoptysis (coughing up blood) may occur, usually in people with underlying lung conditions.

Serious allergic or anaphylactoid reactions may occur, particularly with intravenous use. Treatment should be stopped and immediate medical care sought if symptoms such as difficulty breathing, wheezing, rash, hives, facial swelling, or severe dizziness occur.

Does acetylcysteine make you sleepy?

Acetylcysteine does not typically cause drowsiness. Fatigue or lightheadedness are uncommon and usually related to individual sensitivity or underlying illness rather than the medication itself.

Who should not use it

Acetylcysteine should not be used by anyone with a known allergy to acetylcysteine or to any ingredient in its formulation.

It should be used with caution in people with asthma or reactive airway disease, as bronchospasm can occur. In such cases, pre-treatment with a bronchodilator and close medical supervision are recommended.

Use during pregnancy or breastfeeding should occur only if clearly needed and after discussing the potential risks and benefits with a healthcare provider.

Formulations, strengths and U.S. brands

In the United States, acetylcysteine is available as:

Mucomyst® – acetylcysteine solution for inhalation (10% or 20% concentrations)
Acetadote® – intravenous injection used in hospitals for acetaminophen overdose

Generic acetylcysteine formulations are also available. These products are not for over-the-counter use and must be prescribed by a healthcare professional.

Acetylcysteine: Uses (Inhalation & IV), Dosing & Side Effects