Acetylcysteine Side Effects

Medically reviewed by Drugs.com. Last updated on Jan 24, 2025.

Applies to acetylcysteine: oral capsule, oral solution, oral tablet.

Other dosage forms:

• inhalation solution
• intravenous solution

Precautions

Your doctor will check your progress closely while you are receiving this medicine. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to receive it. Blood and urine tests may be needed to check for unwanted effects.

Serious allergic reactions may occur after receiving this medicine. Tell your doctor right away if you have difficulty with breathing or swallowing, fever, hives, itching skin, rash, nausea, reddening of the skin, especially around the ears, swelling of the eyes, face, or inside of the nose, or unusual tiredness or weakness.

This medicine may increase risk of bleeding in your esophagus and stomach. Tell your doctor if you have severe or ongoing vomiting after taking this medicine.

Common side effects of acetylcysteine

Some side effects of acetylcysteine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Serious side effects of acetylcysteine

Along with its needed effects, acetylcysteine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur while taking acetylcysteine:

For healthcare professionals

Applies to acetylcysteine: compounding powder, inhalation solution, intravenous solution, oral capsule, oral powder for reconstitution, oral tablet, oral tablet effervescent.

General adverse events

The most common adverse events were anaphylactoid reaction, nausea, vomiting, flushing, and skin rash.^[Ref]

Hypersensitivity

• Very common (10% or more): Anaphylactoid reaction (18%)
• Uncommon (0.1% to 1%): Anaphylaxis
• Rare (less than 0.1%): Acquired sensitization
• Frequency not reported: Dermal eruptions^[Ref]

Anaphylactoid symptoms include airway obstruction (bronchospasm), angioedema, dyspnea, hypotension, shock, tachycardia, urticaria, and injection site reaction (including rash). These are most common either during, or at the end of the loading dose infusion, and may be dose related. Careful monitoring is recommended.^[Ref]

Gastrointestinal

• Very common (10% or more): Vomiting NOS (12%)
• Common (1% to 10%): Nausea
• Frequency not reported: Stomatitis^[Ref]

Respiratory

• Common (1% to 10%): Respiratory symptoms, pharyngitis, rhinorrhea, rhonchi, throat tightness
• Frequency not reported: Bronchoconstriction, bronchospasm, irritation to tracheal and bronchial tract (inhalation route), hemoptysis, dyspnea, respiratory arrest, coughing, stridor^[Ref]

Respiratory symptoms were defined as presence of any of the following: cough, wheezing, stridor, shortness of breath, chest tightness, respiratory distress, or bronchospasm.^[Ref]

Cardiovascular

• Common (1% to 10%): Tachycardia
• Uncommon (0.1% to 1%): Hypotension
• Frequency not reported: Cyanosis, tachycardia, bradycardia, cardiac arrest, extrasystoles, flushing, hypertension, vasodilation, ECG changes^[Ref]

Dermatologic

• Common (1% to 10%): Urticaria/facial flushing, rash NOS, pruritus, flushing
• Frequency not reported: Angioedema, sweating, edema periorbital, clamminess^[Ref]

Metabolic

• Common (1% to 10%): Edema
• Frequency not reported: Acidosis, hypokalemia^[Ref]

Other

• Rare (less than 0.1%): Death
• Frequency not reported: Fever, malaise, rigors, chest pain, facial pain, facial edema, raised temperature^[Ref]

Nervous system

• Frequency not reported: Syncope, generalized seizure, drowsiness^[Ref]

Local

• Frequency not reported: Injection site reaction^[Ref]

Musculoskeletal

• Frequency not reported: Arthralgia, arthropathy^[Ref]

Hepatic

• Frequency not reported: Deterioration of liver function^[Ref]

Hematologic

• Frequency not reported: Thrombocytopenia^[Ref]

Ocular

• Frequency not reported: Blurred vision, eye pain, puffy eyes, itching/redness/irritation in eyes (ophthalmic formulation)^[Ref]

Psychiatric

• Frequency not reported: Anxiety^[Ref]

See also:

Frequently asked questions

• What is Fluimucil used for?
• What is NAC and how can it benefit your health?

Further information

Acetylcysteine side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer