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Acetylcysteine (NAC) Uses: Toxicity Antidote & Mucus Relief for Pets

Published on September 10, 2024
Updated on November 5, 2025
Reviewed by Petco's Veterinarian Team
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Acetylcysteine is generally utilized when treating toxicity due to oxidative stress, tissue damage and may be nebulized to break down mucus buildup.

Summary

Used For:

Acetaminophen toxicity, phenol toxicity, mucus buildup

Brands:

Mucomyst

Species:

Dogs and cats

Other names:

N-acetylcysteine, N-acetyl-L-cysteine, NAC, Acetadote, ACC

Drug type:

Antidote

Prescription required:

Yes

Pregnancy and lactation:

Should be safe during pregnancy, unknown if drug is transferred to milk

Side effects:

GI upset, hives, chest tightness, bronchoconstriction, bronchial or tracheal irritation

General description

Acetylcysteine may be used as an antidote to acetaminophen, xylitol and phenol toxicities. It can also be nebulized to break down mucus buildup.

While many medications are often administered for ‘off-label’ or 'extra-label' use in veterinary medicine, it is important to know that off- or extra- label use of a medication can only be done by a veterinarian when there are no other more appropriate medications for a particular pet's circumstances. Your veterinarian must also know all vitamins, supplements, medications etc. your pet is taking to help avoid complications. You must also be sure to follow all instructions provided by your vet carefully and consult your veterinarian with any questions or concerns if they arise.

Uses

Acetaminophen toxicity, phenol toxicity, mucus buildup.

How it works

Acetylcysteine may reduce the extent of liver injury or methemoglobinemia after ingestion of acetaminophen by providing an alternate substrate for metabolization. When administered into the pulmonary tree, acetylcysteine reduces the viscosity of mucoid secretions and expedites their removal through coughing.

Dosage

Dogs and cats, for acetaminophen toxicity: oral loading dose of 140 milligrams per kilogram (diluted to 5% solution) followed by 70 milligrams per kilogram by mouth every 6 hours for 7 treatments; should be spaced from activated charcoal administration by 2-3 hours.

Dogs and cats, for respiratory use: 50 milliliters per hour for 30-60 minutes every 12 hours by nebulization.

  • Information provided above outlines what a typical dose might look like. Always consult your veterinarian on the appropriate dose for your specific animal when using any vitamin, supplement, off-label or prescription products. Some vets may prescribe outside of these ranges based on specific needs of the patient.

Forms

Available in a 10% and 20% solution in 4, 10, 30 and 100 milliliter vials.

Storage information & handling

Review label for detailed instructions specific to the product. When unopened, store at room temperature. After opening, vials should be kept refrigerated and used within 96 hours. Products labeled for IV use should be discarded after 24 hours.

What results can I expect?

When used for toxicities, results will often depend on the amount time between toxic exposure and treatment, condition of the animal and may not be immediately evident. When used for mucus buildup, results should be expected with the first couple of doses.

Missed Dosage

If a dose is missed, continue with the next dosage at the scheduled time. Never administer doses back-to-back, if it is nearly time for the next dose skip the missed dose and continue with the scheduled timing provided by your veterinarian.

Overdose / acute toxicity

Other than the common side effects, the drug is considered safe in most overdose situations.

Side effects

Oral administration:

  • GI effects (nausea and vomiting
  • Urticaria (hives)

Inhaled administration:

  • Chest tightness
  • Bronchoconstriction
  • Bronchial or tracheal irritation

Contraindications

*Do not use in cases of a known hypersensitivity.

Drug interactions

Acetylcysteine may be inactivated by activated charcoal. Use caution with nitroglycerin.

Precaution

Do not delay administration of acetylcysteine in cats with acetaminophen ingestion due to their rapid development of methemoglobinemia after acetaminophen ingestion.

Should be administered by gastric or duodenal tube in toxicity treatments. Use with caution in pets with liver or kidney disease.

Sources

Plumb’s Veterinary Drug Handbook

Pfizer - Acetylcysteine

Disclaimer
The information contained on this page is for educational purposes only. This medication should only be given under the advice of a veterinarian who has examined your pet under the laws applicable to your state of residence.

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