nac

N-acetylcysteine (NAC) is a supplement form of the amino acid cysteine. According to the NIH Office of Dietary Supplements, it works as an antioxidant and helps thin and clear mucus along the airways, including the mouth, nose, throat, and lungs. ODS adds that NAC may also support the immune system, help the body fight viruses, and ease inflammation, though these effects are described as possibilities rather than established facts.

The NIH Office of Dietary Supplements states that NAC may help ease the severity of symptoms in bronchitis, chronic obstructive pulmonary disease (COPD), and related conditions that affect breathing, but it notes that NAC's effects on COVID-19 remain unclear. ODS cites one small study in which hospitalized patients with moderate or severe COVID-19 took 600 mg of oral NAC twice daily for two weeks and had a lower chance of needing a ventilator or dying. In a separate trial, intravenous NAC (which ODS classifies as a drug rather than a supplement) did not reduce ICU admissions, time spent in the ICU, ventilator use, or deaths. More broadly, both ODS and NCCIH state that research has not clearly shown that any dietary supplement can prevent COVID-19 or reduce the severity of its symptoms. These are preliminary findings, not proof that NAC treats any of these conditions.

There is no official Recommended Dietary Allowance for NAC as a supplement, and NIH does not provide a general recommended dose. The single COVID-19 study cited by ODS used 600 mg twice daily for two weeks in hospitalized patients, but that is a research dose in a specific clinical setting and does not establish a safe or effective dose for everyday use. Because NAC may affect blood clotting and blood pressure and can interact with medications, talk with your doctor or pharmacist before starting it, especially if you take prescription drugs or have a health condition.

The NIH Office of Dietary Supplements notes that NAC may interfere with blood clotting and may lower blood pressure, so extra caution is warranted for people with bleeding concerns or those taking medications that affect clotting or blood pressure. As with any supplement, let all of your health care providers know you are using NAC, and do not rely on it as a substitute for medical care for a breathing problem or any other condition.

According to NIH ODS, reported side effects of NAC can include nausea, vomiting, stomach pain, diarrhea, indigestion, and heartburn.

NIH ODS notes that combining NAC with nitroglycerine (a medication used to treat chest pain) may cause low blood pressure and severe headaches. Because NAC may also affect blood clotting and lower blood pressure, discuss possible interactions with your clinician, particularly if you take blood thinners or blood pressure medications.