For Patients & Caregivers
How It Works
N-acetylcysteine is used as a drug for acetaminophen overdose and to help break up mucus. It has not been proven to be an effective treatment for cancer.
N-acetylcysteine (NAC) is a dietary supplement derived from the amino acid L-cysteine. It is used as an antidote for acetaminophen overdose. As an antioxidant, it is thought to reduce DNA damage. NAC is also marketed for its liver-protective properties and to support healthy immune functioning.
In humans, NAC can dissolve and loosen mucus caused by some respiratory disorders. It has also been studied for several psychiatric disorders with limited success. Small trials suggest potential to reduce cancer-treatment toxicities, but it has not been shown to treat cancer. Additional studies are needed to determine safety and efficacy of NAC for various conditions.
To treat drug-induced liver toxicity
NAC is an effective treatment for acetaminophen poisoning, which can be life-threatening. If liver toxicity is suspected, seek immediate medical attention for proper treatment.
To treat chronic lung disease
Study results are mixed. Some trials suggest it may reduce inflammation, flare-ups, or improve lung function, but benefits were not observed in other trials.
To treat HIV and AIDS
A few trials suggest that NAC can raise cysteine and glutathione levels in HIV+ patients, but whether it improves survival or immune function is not known.
To treat depression
Results with NAC as add-on therapy for depression are mixed. Additional studies are needed.
To prevent and treat cancer
A few clinical trials suggest that this supplement can prevent certain pre-cancerous damage, but there is no proof that it can prevent cancer.
To reduce cancer treatment side-effects
A few initial studies suggest possible benefit to reduce some toxicities and symptoms, but more studies are needed to determine safety and effectiveness.
Do Not Take If
- Stomach upset
- Eye irritation
- Skin rash
Less common: Low blood pressure, anaphylactic shock, asthma attacks, headache
Light sensitivity: Occurred in pulmonary fibrosis patients taking NAC in combination with pirfenidone. The reaction could not be explained by other variables such as location, season, or other medications taken at the same time.
- It is controversial whether antioxidants like NAC can lessen or negate cancer treatment effects. Because some cancer therapies work by creating free radicals that kill cancer cells, high levels of antioxidants may neutralize these effects and protect cancer cells from these therapies. So what protects healthy cells may protect cancer cells as well. Patients who are interested in taking antioxidants during therapy should consult with their oncologist.
For Healthcare Professionals
N-acetylcysteine (NAC) is an antioxidant that is used as a prescription drug and as a dietary supplement. As a drug, it is given parenterally or orally to treat acetaminophen overdose. The inhalant and oral solution forms have a mucolytic effect, and are used to relieve obstructions in bronchial diseases and in tracheotomy procedures. The oral capsule is marketed as a dietary supplement for its liver-protective properties and to support healthy immune functioning.
Clinical studies show that NAC can treat drug-induced hepatotoxicity (1) (2). Preliminary data suggest it can also improve antioxidant levels in patients with HIV/AIDS (3) and preserve renal function in hemodialysis patients (40) (41).
Results with NAC for chronic lung disease are mixed. Some studies indicate that it may reduce exacerbations (5) (44), inflammation (45), and help improve or maintain lung function (6) (38), but such benefits were not observed in other trials (7) (8) (37) (39). In addition, a meta-analysis suggests it is not the most effective mucolytic agent for chronic obstructive pulmonary disease (COPD) (46).
There has also been interest in NAC to improve psychiatric conditions, with preliminary benefit shown for addiction, substance abuse, and compulsive disorders (11) (12) (13) (14), but effects of adjunctive NAC on depressive symptoms are mixed (47) (48) (49).
Although small studies suggest that NAC may inhibit cancer biomarker development (15) (16), a large trial found it did not inhibit formation of secondary head and neck or lung tumors (17). Preliminary findings suggest possible benefit with NAC for cancer-treatment toxicities such as reduced liver toxicity (4), neuropathy (18), and mucositis (43) (50), although it did not reduce oxidative stress (42) or cisplatin toxicities (51).
Gastrointestinal side effects have been reported following use of NAC (19). Due to its antioxidant activity, it may also accelerate the progression of some cancers evidenced by accelerated lung cancer growth in an animal model (36). Additional studies are therefore needed to determine safety and efficacy.
Mechanism of Action
NAC is a precursor to glutathione (GSH). It is used as both an antidote for acetaminophen-induced hepatotoxicity, and as a mucolytic agent for respiratory diseases. NAC reduces disulphide bonds to sulfhydryl bonds to reduce mucus formation (20). Its hepatoprotective action may occur by cytokine-mediated mechanisms as well as GSH replenishment (21). NAC crosses the blood-brain barrier, increases brain GSH levels, and acts as a glutamine modulator (11).
In vitro, NAC improved ifosfamide benefits by decreasing nephrotoxicity without reducing antitumor effects (26). NAC altered doxorubicin-induced NF-κB activity via concentration-dependent anti- and pro-oxidant mechanisms (27). This biphasic effect was also time-dependent (28). In androgen-independent human prostate cancer PC-3 cells, antiproliferative effects were attributed to upregulated Cyr61 protein expression (28).
NAC amide can increase bioavailability and reduce oxidative stress, but it does not decrease doxorubicin-induced cell death in H9c2 cardiomyocytes (29). In an animal model, NAC increased lung cancer cell proliferation due to its antioxidant activity by reducing ROS, DNA damage, and p53 expression (36).
Photosensitivity not attributable to location, season, or concomitant medication: Occurred among pulmonary fibrosis patients more frequently with acetylcysteine than placebo in combination with pirfenidone (39).