N-acetylcysteine Side Effects, Interactions and Health Warnings

There are few N-acetylcysteine side effects to be concerned about and this supplement is usually well-tolerated when used appropriately.

N-acetylcysteine (N-acetyl cysteine, NAC) is a derivative of the amino acid L-cysteine. It is the most important constituent needed for the production of glutathione, the body’s master antioxidant-controlling substance.

Eating cysteine rich foods and/or supplementing with oral tablets may help to elevate glutathione levels somewhat. However oral and intravenous administration of NAC produces greater increases in the liver’s production of glutathione.

As a natural health supplement, it is taken to support the health of the liver and to combat the aging process. It is used by doctors to counteract the poisonous effects of acetaminophen toxicity, as well as for numerous other therapeutic purposes.

The most common N-acetylcysteine side effects include headaches, nausea, vomiting and/or diarrhea. In rare cases of heavy dosing, other side effects have been noted.

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Dosage:

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N-Acetylcysteine Side Effects

N-acetyl cysteine is a natural compound that is produced in the body from the cysteine content in foods that we eat. Our bodies are also capable of synthesizing cysteine on their own.

For these reasons, N-acetylcysteine is quite safe to take at low dosages. Almost no side effects are reported when using this supplement at low dosages. This compound has also been approved by the FDA.

However, in certain individuals or when taken at high doses, adverse effects may occur. Concerning N-acetylcysteine side effects that affect the cardiovascular system, the following has been reported:

• In a single case, two daily oral NAC doses at 600 mg per caused heart palpitations.
• In one study involving 11 human subjects, diastolic and systolic blood pressure levels increased significantly in a treatment group receiving NAC daily over a placebo group.
• Tachycardia has been noted in two trials.
• In a single case, transient, severe sinus bradycardia was observed.
• In two randomized, placebo-controlled trials, chest tightness was noted with doses of 600 mg daily, divided into three equal doses. Angina was also noted in one study at the same dosing schedule.

Side Effects for Skin

Cysteine forms an important component of healthy skin. However, in rare cases, taking N-acetylcysteine has been linked with the following dermatological side effects:

• Urticarial exanthema and facial edema;
• Flushing and rashes;
• Erythematous flare and facial muscle fatigue;
• Facial erythema and palmar erythema;
• Sweating and pruritus;
• Inflammation, pain and excoriation of the skin.

Gastrointestinal Side Effects

Randomized, controlled clinical trials have reported the occurrence of the following gastrointestinal side effects associated with N-acetylcysteine administration. These side effects are more likely when taking high dosages of this supplement intended for specific therapeutic targets.

• Epigastralgia in roughly 3% of patients;
• Flatulence;
• Bad (metallic) tastes in mouth;
• Loss of appetite;
• Constipation and diarrhea;
• Heartburn, nausea and vomiting;
• Intolerance to certain odors and/or tastes;
• Dry mouth and dyspepsia;
• Hemorrhages in bowel mucosa.

Additional Side Effects of NAC

Concerning the hematological side effects of NAC, decreased prothrombin times, decreased platelet aggregation capacities, lengthened coagulation times and increased bleeding have been noted.

In the musculoskeletal system, N-acetylcysteine side effects may include pains in the legs, and increases in pre-existing joint pains.

Possible CNS and neurological side effects of NAC administration include dizziness, tiredness and encephalopathy (decreased brain functioning). Also, some randomized, double-blind crossover trials have shown NAC to cause an inability to focus and disorientation.

Further, dystonic reactions have been noted in patients receiving NAC intravenously. Finally, cyanosis (skin lacking oxygen) has been observed in two cases involving premature infants. Increased degradation of bulbar functioning has also been noted in patients being treated for amyotrophic lateral sclerosis.

Concerning possible ocular/otic side effects, blurred vision has been noted in one open-label study. Additionally, cortical blindness and status epilepticus have been noted in a single case involving a 2-year old female. Notably, her vision had nearly recovered completely by her 18-month follow-up analysis.

Possible, but unlikely N-acetylcysteine side effects concerning psychiatry include dysphoria (generalized dissatisfaction with living) and psychosomatic chronic fatigue.

In the respiratory/pulmonary system, NAC side effects may include wheezing, bronchospasms and increased sputum levels. This is especially true in cases involving treatment for fibrosing alveolitis. Coughing has also been noted in various studies.

During treatment for chronic bronchitis, NAC has also caused dyspnea (difficulties breathing). One sixteen year old female experienced respiratory arrest during intravenous administration of NAC for acetaminophen toxicity treatment. Decreased tolerance to exercise, sore throat, chest pains and common cold symptoms have also been noted.

Deficient magnesium levels have also been associated as possible N-acetylcysteine side effects. Also, injection site burning in intravenous applications of NAC, and fever have been reported.

Again, the most common N-acetylcysteine side effects are nausea, vomiting, headache and/or diarrhea. Other possible side effects of NAC occur very infrequently.

Conclusions

Except for when taken in highly excessive dosages, NAC administration is accepted as likely safe. Physicians use N-acetylcysteine to rapidly increase the synthesis of glutathione, and improve the body’s protection from cases of excessive toxicity. When side effects are experienced in association with NAC administration, they are almost always mild and pass quickly.

There are possible negative interactions between NAC and other drugs. Also, NAC may not mix well with certain herbal agents. N-acetylcysteine administration is not recommended for women who are pregnant or nursing.

Further, there are certain other groups of patients who are not recommended for use. Speak with your doctor about possible benefits and N-acetylcysteine side effects that may pertain to your specific healthcare scenario.

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