Mucomyst Side Effects

Generic Name: acetylcysteine

Note: This page contains information about the side effects of acetylcysteine. Some of the dosage forms included on this document may not apply to the brand name Mucomyst.

Not all side effects for Mucomyst may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to acetylcysteine: inhalation solution

In addition to its needed effects, some unwanted effects may be caused by acetylcysteine (the active ingredient contained in Mucomyst). In the event that any of these side effects do occur, they may require medical attention.

If any of the following side effects occur while taking acetylcysteine, check with your doctor or nurse as soon as possible:

Less common
  • Wheezing, tightness in chest, or difficulty in breathing (especially in asthma patients)
  • Skin rash or other irritation

Some of the side effects that can occur with acetylcysteine may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

Less common
  • Clammy skin
  • fever
  • increase in amount of mucus in lungs
  • irritation or soreness of mouth, throat, or lungs
  • nausea or vomiting
  • runny nose

For patients using a face mask for inhalation of acetylcysteine: the mask may leave a stickiness on your face. This can be removed with water.

When you use acetylcysteine, you may notice that the medicine has an unpleasant odor at first. However, this smell will go away soon after you use the medicine.

For Healthcare Professionals

Applies to acetylcysteine: compounding powder, inhalation solution, intravenous solution, oral capsule, oral tablet


Gastrointestinal side effects reported after oral administration have included nausea, vomiting, diarrhea, heartburn, dyspepsia, rectal bleeding, and epigastric pain. Stomatitis, hemoptysis, and rhinorrhea have been associated with the use of nebulized acetylcysteine (the active ingredient contained in Mucomyst) [Ref]


Allergic reactions to intravenous use have occurred. Symptoms have included urticarial rash, pruritus, flushing, a warm feeling of the skin, occasional bronchospasm or hypotension, angioedema, dyspnea, a serum sickness-like reaction, and asthma.[Ref]


Respiratory side effects, including bronchospasm, wheezing, precipitation of asthma, and respiratory arrest, have been reported after respiratory or intravenous administration. Hemoptysis rarely occurs.[Ref]

Nervous system

CNS side effects of dizziness, drowsiness, lightheadedness, and asthenia have occurred with oral use. Headache and increased intracranial pressure have been reported rarely.[Ref]


One case of ST segment depression, chest pain, and T-wave inversion was associated with an anaphylactoid reaction to intravenous acetylcysteine (the active ingredient contained in Mucomyst) [Ref]

Cardiovascular side effects of tachycardia and hypotension have been reported in patients with hypersensitivity to acetylcysteine.[Ref]


Skin rashes and pruritus have been reported. Skin reactions are a common presentation of hypersensitivity to intravenous administration.[Ref]

Rashes seen after intravenous therapy usually consist of transient flushing on the upper trunk, neck and face. Rashes sometimes were urticarial and pruritic.[Ref]


Local reactions to injectable 20% acetylcysteine (the active ingredient contained in Mucomyst) solution extravasation include severe pain and excoriation.[Ref]


Fever is a rarely occurring side effect seen after both inhalation and intravenous administration.[Ref]


Musculoskeletal side effects have rarely included myalgia and arthralgia.[Ref]


Elevated serum transaminase levels were temporally associated with acetylcysteine (the active ingredient contained in Mucomyst) administration in a patient with cystic fibrosis. At the dose used for acetaminophen toxicity, acetylcysteine does not have hepatotoxic effects.[Ref]


Hematologic side effects have included increased blood loss and use of blood products when acetylcysteine (the active ingredient contained in Mucomyst) was used to prevent perioperative inflammation and ischemia-reperfusion injury during cardiac surgery.[Ref]


1. Mann KV "Treatment of acetaminophen overdose when oral acetylcysteine therapy is not tolerated." Clin Pharm 7 (1988): 563-4

2. Jackson IM, Barnes J, Cooksey P "Efficacy and tolerability of oral acetylcysteine (Fabrol) in chronic bronchitis: a double-blind placebo controlled study." J Int Med Res 12 (1984): 198-206

3. Vale JA, Wheeler DC "Anaphylactoid reaction to acetylcysteine ." Lancet 2 (1982): 988

4. Gervais S, Lussier-Labelle F, Beaudet G "Anaphylactoid reaction to acetylcysteine ." Clin Pharm 3 (1984): 586-7

5. Sunman W, Hughes AD, Sever PS "Anaphylactoid response to intravenous acetylcysteine ." Lancet 339 (1992): 1231-2

6. Bateman DN, Woodhouse KW, Rawlins MD "Adverse reactions to N-acetylcysteine ." Lancet 2 (1984): 228

7. Bateman DN, Woodhouse KW, Rawlins MD "Adverse reactions to N-acetylcysteine." Hum Toxicol 3 (1984): 393-8

8. Mant TG, Tempowski JH, Volans GN, Talbot JC "Adverse reactions to acetylcysteine and effects of overdose." Br Med J (Clin Res Ed) 289 (1984): 217-9

9. Dawson AH, Henry DA, McEwen J "Adverse reactions to N-acetylcysteine during treatment for paracetamol poisoning." Med J Aust 150 (1989): 329-31

10. Mohammed S, Jamal AZ, Robison LR "Serum sickness-like illness associated with N-acetylcysteine therapy." Ann Pharmacother 28 (1994): 285

11. Millman M, Grundon W "Use of acetylcysteine in bronchial asthma and emphysema." J Asthma Res 6 (1969): 199-209

12. Vale JA, Buckley BM "Asthma associated with N-acetylcysteine infusion and paracetamol poisoning ." Br Med J (Clin Res Ed) 287 (1983): 1223

13. Ho SW, Beilin LJ "Asthma associated with N-acetylcysteine infusion and paracetamol poisoning: report of two cases." Br Med J (Clin Res Ed) 287 (1983): 876-7

14. Smilkstein MJ, Bronstein AC, Linden C, Augenstein WL, Kulig KW, Rumack BH "Acetaminophen overdose: a 48-hour intravenous N-acetylcysteine treatment protocol." Ann Emerg Med 20 (1991): 1058-63

15. "Mucolytic agent." Br Med J 2 (1966): 603-4

16. Reynard K, Riley A, Walker BE "Respiratory arrest after N-acetylcysteine for paracetamol overdose." Lancet 340 (1992): 675

17. Massey DG, Carpenter GB "Febrile reaction to inhaled acetylcysteine." Chest 89 (1986): 887-8

18. Bonfiglio MF, Traeger SM, Hulisz DT, Martin BR "Anaphylactoid reaction to intravenous acetylcysteine associated with electrocardiographic abnormalities." Ann Pharmacother 26 (1992): 22-5

19. Venturelli J, Tein I, Hollenberg R "Increased intracranial pressure associated with N-acetylcysteine inhalation therapy ." Crit Care Med 12 (1984): 926-7

20. Simpkin DM, Milner R, Snell AP "Continuous subcutaneous apomorphine infusion in Parkinson's disease." Med J Aust 156 (1992): 883-4

21. Casola G, vanSonnenberg E "Skin damage from acetylcysteine leak during percutaneous abscess drainage." Radiology 152 (1984): 233

22. Beckett GJ, Donovan JW, Hussey AJ, Proudfoot AT, Prescott LF "Intravenous N-acetylcysteine, hepatotoxicity and plasma glutathione S- transferase in patients with paracetamol overdosage." Hum Exp Toxicol 9 (1990): 183-6

23. Wijeysundera DN, Karkouti K, Rao V, et al. "N-acetylcysteine is associated with increased blood loss and blood product utilization during cardiac surgery." Crit Care Med 37 (2009): 1929-34

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.