Acetylcysteine

GoodRx

Acetylcysteine 5%, 10%, 20% · oral solution

Dry Eye/OSD

Approved uses

Abnormal, viscid, or inspissated mucous secretions in acute and chronic bronchopulmonary disease, cystic fibrosis, and tracheostomy care

Nebulized 3 to 5 mL of the 20% solution 3 to 4 times daily (range 1 to 10 mL every 2 to 6 hours), or 1 to 2 mL by direct instillation every 1 to 4 hours

Acetaminophen overdose, to prevent or lessen hepatic injury

140 mg/kg PO loading dose diluted to 5% with a diet soft drink, first maintenance dose of 70 mg/kg 4 hours later, 17 doses total; start within 24 hours of ingestion

OFF-LABELNot in the FDA label for this product

Filamentary keratitis, refractory

Compounded topical solution 5% to 10% QID, the most commonly reported ocular regimen; the cited case report used 10%

Case report · uncontrolled

Weak and uncontrolled. A single case report of recurrent filamentary keratitis refractory to lubricants, punctal plugs, steroids, and lid hygiene showed complete filament resolution and symptom relief sustained at 10 months on a compounded 10% solution given with preservative-free ointment and oral doxycycline, and a systematic review of 106 ocular studies found 5% to 10% four times daily the most common regimen with rare corneal necrosis at higher concentrations.

Crist AJ. Case Report: Management of Refractory Filamentary Keratitis with N-acetylcysteine. Optom Vis Sci. 2021;98(6):547-551. Concentration and frequency range from Eghtedari Y, Oh LJ, Di Girolamo N, Watson SL. The role of topical N-acetylcysteine in ocular therapeutics. Surv Ophthalmol. 2022;67(2):608-622 (doi 10.1016/j.survophthal.2021.07.008).

Mucus fishing syndrome

Compounded 5% topical solution. The two-case report states no frequency; the commonly reported ocular regimen for this drug is 5% to 10% QID.

2 case reports · confounded

Very weak. Two case reports used topical 5% inside a multimodal regimen of topical corticosteroid, lid hygiene, and low-level light therapy, and the authors state the contribution of the light therapy cannot be determined from these findings alone, and the acetylcysteine contribution is likewise unisolated.

Mancini A, Carnovale-Scalzo G, Mancini M, et al. Low-Level Light Therapy as a Potential Adjunctive Approach in Mucus Fishing Syndrome: Report of Two Clinical Cases. Int Med Case Rep J. 2025;18:1679-1684.

Contraindications

Hypersensitivity to acetylcysteine.
None for oral use in acetaminophen overdose.

Available Forms

Oral solution, 20% (200 mg/mL), 30 mL rubber-stoppered glass vials, cartons of three

Mechanism of Action

The free sulfhydryl group opens disulfide linkages in mucus glycoproteins and lowers viscosity; activity is pH dependent, occurring between pH 7 and 9, and is unaltered by DNA content. Applied topically it thins and loosens adherent corneal mucus filaments, with reviews also crediting hydroxyl radical scavenging and modulation of inflammatory cascades on the ocular surface.

Warnings & Precautions

No ophthalmic formulation: This label covers a 20% solution for inhalation and oral use; every ocular application is off-label and requires compounding.
Unpreserved solution: No antimicrobial agent is present; refrigerate the remainder of an opened vial and discard after 96 hours.
Solution color change: A light purple color in an opened container is a chemical reaction and does not significantly affect safety or mucolytic potency.
Bronchospasm: Asthmatics require close observation; most cases are relieved quickly by a nebulized bronchodilator, and progression warrants immediate discontinuation.
Airway secretion volume: Liquefied bronchial secretions increase after administration, and inadequate cough requires mechanical suction to keep the airway open.
Generalized urticaria: Reported rarely with oral use for acetaminophen overdose; discontinue unless treatment is essential and the allergic symptoms can be otherwise controlled.

Common Side Effects

Ocular: Corneal necrosis is rare and has been reported at higher topical concentrations; this label lists no ocular adverse effects.
Systemic, inhalation: Bronchospasm, chest tightness, stomatitis, rhinorrhea, nausea, vomiting, fever, drowsiness, clamminess; overt bronchospasm is infrequent and unpredictable, even in patients with asthmatic bronchitis.
Systemic, oral: Nausea, vomiting, and other GI symptoms, especially at the large doses used for overdose; rash with or without mild fever, rare.
Hypersensitivity: Acquired sensitization reported rarely, confirmed in inhalation therapists with frequent extended dermal exposure.

Pregnancy & Lactation

Pregnancy: Rat and rabbit reproduction studies at up to 2.6 times the human mucolytic dose showed no teratogenicity and no evidence of impaired fertility or fetal harm; there are no adequate and well-controlled studies in pregnant women.

Lactation: Excretion in human milk is unknown.

Pediatric Use

No studies