N-Acetyl-L-Cysteine (NAC) is the acetylated derivative of amino acid cysteine.
NAC is also known as acetyl cysteine, acetylcysteine, N-acetyl-B-cysteine, N-acetyl-cysteine, and N-acetylcysteine.
NAC is available as a prescription and as a supplement. The prescription forms of NAC are used as a mucolytic drug and to treat acetaminophen overdose.
Once in the body, NAC is rapidly hydrolyzed to cysteine. NAC does not accumulate in the body but its oxidized forms and metabolites are found in the body.
Studies in mice have demonstrated that radiolabeled NAC is able to cross the blood-brain barrier.5 It is thought that NAC is also able to cross the blood-brain barrier in humans.
N-Acetyl-L-Cysteine can be a precursor to intracellular glutathione. Glutathione is an antioxidant tripeptide that protects cells from reactive oxygen species.
Animal studies suggest that NAC can help protect cognitive function, possibly through activity of NAC as an antioxidant or maintenance of neurotransmitter concentrations.5,6
Common adverse reactions to NAC include gastrointestinal complaints, diarrhea, nausea, vomiting, fatigue, conjunctival irritation, and skin rash. Hypotension, anaphylaxis, asthma attacks, and headache have been rarely reported.
N-Acetyl-L-Cysteine should not be taken by anyone who is pregnant or breast-feeding, allergic to acetylcysteine, or who has asthma.
Nitroglycerin: Consumption of NAC and nitroglycerin can increase hypotension, headache, and worsen temporal artery dilation. NAC should not be taken by people who are taking nitroglycerin.
Information on the relationship between substances and disease is provided for general information, in order to convey a balanced review of the scientific literature. In many cases the relationship between a substance and a disease is tentative and additional research is needed to confirm such a relationship.
Controlled trial of N-acetylcysteine for patients with probable Alzheimer's disease.
A randomized, double-blind, placebo-controlled trial investigated the affects of N-acetyl-L-cysteine (NAC) in people with prabable Alzheimer's disease. Forty-three people who met the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria 8 for probable AD; Mini-Mental State Examination (MMSE) scores for potential participants fell between 12 and 26. Participants took a series of psychometric tests at baseline, 12 weeks, and 24 weeks. Participants were randomly assigned to receive 50 mg/kg NAC daily or a placebo for the duration of the trial. Although no significant affects on the primary outcome measure (6-month change scores on the MMSE and a scale that assessed basic and instrumental activities of daily living) were detected, significant affects on the secondary outcome measures were identified. Participants receiving NAC showed significantly better performance on the letter fluency task compared to placebo; for those in the NAC group, scores on the Wechsler Memory Scale immediate figure recall showed a trend toward improvement (p=0.067). The results of this small trial suggest that NAC may have beneficial effects for people with probable Alzheimer's disease. These results support initiation of a larger trial to further evaluate these outcomes.3
N-acetyl cysteine for depressive symptoms in bipolar disorder--a double-blind randomized placebo-controlled trial.
A randomized, placebo-controlled, double-blind trial investigated the efficacy of N-acetyl-L-cysteine with normal drug treatment for depressive symptoms of bipolar disorder. Seventy-five people with bipolar disorder participated in the 24 week trial followed by a 4 week washout. Participants were randomly assigned to receive either 2 g NAC or a placebo daily. After 8 weeks of supplememt use, benefits were evident for the NAC group on the Global Assessment of Functioning Scale and Social and Occupational Functioning Assessment Scale. A significant improvement on the Montgomery Asberg Depression Rating Scale (MADRS) was noted in the NAC group (least squares mean difference [95% confidence interval], -8.05 [-13.16, -2.95], p=0.002). NAC supplements had no effect on time to a mood episode (log-rank test, p=0.968). This preliminary trial suggests that further study of the effects of NAC on bipolar disorder symptoms are warranted.1
Effects of folic acid and N-acetylcysteine on plasma homocysteine levels and endothelial function in patients with coronary artery disease.
A randomized, placebo-controlled, blinded study investigated the effects of folic acid or N-acetyl-L-cysteine on plasma homocysteine and endothelial function. Sixty people with coronary artery disease participated in the 8 week trial. Participants were randomized to receive 5 mg folic acid, 600 mg NAC, or placebo daily. Both folic acid and NAC reduced plasma homocysteine concentrations compared to placebo (from 21.7±8.7 umol/L to 12.5±2.5 umol/L, P<0.001; from 20.9±7.6 umol/L to 15.6±4.3 umol/L, P=0.03, respectively). Endothelium-dependent dilation was increased by folic acid and NAC (6.7±6.1% P=0.002, 4.4±2.6% P<0.001, respectively); the difference between folic acid and NAC for EDD was not statistically significant. This study indicates that folic and NAC are effective at lowering homocysteine concentrations and may be useful for people with high homocysteine and coronary artery disease. Further studies are warranted.2
Urinary and plasma homocysteine and cysteine levels during prolonged oral N-acetylcysteine therapy.
A small trial investigated the affects of N-acetyl-L-cysteine supplements on plasma homocysteine and cysteine levels. The trial consisted of a one-month supplemented period, a one-month washout period; and a two-month supplemented period. Forty healthy female volunteers participated in the trial. During the one-month supplemented period, participants were divided into three groups: no supplement (group A; n=13), 600 mg NAC/day (group B; n=14), and 1800 mg NAC/day (group C; n=14). After one month, group A showed no difference in plasma total homocysteine and total cysteine from baseline. Group B showed a significant decrease in plasma total homocysteine after one month of supplementation with 600 mg NAC daily (about -10% from baseline; p<0.05 compared to baseline). Group C showed a greater decrease in plasma total homocysteine versus placebo after supplementation with 1800 mg NAC daily for one month (about -21% from baseline; p<0.01). After supplementation was discounted, values returned to baseline. When all groups were supplemented with 1800 mg NAC/day, plasma total homocysteine decreased significantly (about 20-25% with respect to baseline), whereas free homocysteine and reduced homocysteine showed both an absolute and a relative increase. Total cysteine tended to increase over time (+10-15% versus baseline; p<0.01). The results of this study suggest that NAC be effective for moderating homocysteine levels in healthy women. Further studies are warranted.4
The dietary supplement information contained on this site has been compiled from published sources thought to be reliable, but it cannot be guaranteed. Efforts have been made to assure this information is accurate and current. However, some of this information may be purported or outdated due to ongoing research or discoveries. The authors, editors and publishers cannot accept responsibility for errors or omissions or for any consequences from applications of the information in this site and make no warranty, expressed or implied, with respect to the contents herein.
Print this page
Contact an Expert
Herbs
