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SHOP FOR RELATED PRODUCTS
Cysteine is a sulfur-containing, water-soluble amino acid that
is found in many proteins. Cysteine is considered a non-essential
amino acid because it is formed from methionine in the body.
Cysteine is very unstable and is readily oxidized to the amino
acid cystine. Cystine contains two cysteines linked with a disulfide
bond. It is thought that both amino acids probably undergo similar
reactions in the body.
Cysteine may be metabolized by several routes to yield pyruvate,
taurine, or sulfide and sulfate. Insulin, CoA, glutathione (GSH),
and vasopressin are other important sulfur-containing compounds
derived from cysteine and cystine.
Cysteine helps to detoxify harmful toxins and protect the body
from radiation damage. It is one of the best radical destroyers,
and works best when taken with vitamin E and selenium.
Since Cysteine is more soluble than cystine, it is used more readily
in the body and is usually best for treating most illnesses. Vitamin
B6, vitamin B12 and folate are necessary for cysteine synthesis,
which may not take place ias it should in people with chronic illnesses.
People with chronic illnessess may need higher doses, as much as
1,000 mg three times daily for a month at a time.
Cysteine is also a precursor to gultathione, a substance that detoxifies
the liver by binding with potentially harmful substances there.
It helps to protect the liver and brain from damge due to alcohol,
drugs, and toxic compounds in cigarette smoke. It is a generally
accepted treatment for a type of liver failure that sometimes results
from acetaminophen (Tylenol) poisoning. This ability to detoxify
some chemicals makes it a lifesaver against certain drug overdoses
and toxic metal poisoning.
The cysteine derivative N-acetyl-L-cysteine (NAC) helps prevent
cellular oxidative damage in two ways: first, as an antioxidant
capable of scavenging non-peroxyl radicals and, secondly, as a substrate
for GSH synthesis. NAC has been used for a number of therapeutic
purposes including treating respiratory diseases, acetaminophen
poisoning, angina pectoris, and glutathione/antioxidant replenishment
in HIV/AIDS. Newer research suggests an additional benefit in helping
prevent cardiovascular disease and treating ocular symptoms in Sjogren's
syndrome. Preliminary research indicates that N-acetylcysteine may
have a therapeutic benefit on ocular symptoms, such as ocular soreness
and irritability, associated with Sjogren's syndrome.
NAC may be used in place of L-cysteine. NAC has been shown to be
more effective at boosting glutahione levels than supplements of
cystine or even of glutathione itself.
NAC helps with respiratory impairment in several ways. Conventional
medicine uses it widely in inhalants to ward off asthma attacks.
It is effective against simple colds and bronchial infections, by
working to break up mucus. In a dosage of 1.8 grams a day, NAC was
shown to help people with pulmonary fibrosis. It may be the treatment
of choice in the often fatal adult respiratory distress syndrome
(ARDS).
The lack of sulfur in low-fat diets can cause hair loss, particularly
in women. NAC is one of the best sulfur-containing supplements,
and dosages as high as 5 grams per day can stop hair from falling
out. Sometimes the hair may even grow back.
As a heart supplement NAC is indispensable. It eliminates the cardiovascular
threat posed by lipoprotein (a), a product of cholesterol metabolism
recognized only within the last few years as an independent risk
factor in heart diseases. In doses of 2-4 grams a day, NAC brings
lipoprotein(a) down to a less threatening level.
Deficiency: Hair loss in women, among older people
lower levels are closely associated with risks of heart diseases,
diabetes, and arthritis.
Sources: Wheat germ, granola, oat flakes, ricotta,
cottage cheese, yogurt, pork, sausage meat, chicken, turkey, duck
and luncheon meat.
Precautions: Taking high doses (over 7 g) of cysteine
may be harmful and should be avoided.
Oral NAC treatment may cause nausea, vomiting, and diarrhea.
NAC infusion in acetaminophen poisoning may cause anaphylactoid
reactions including angioedema, bronchospasm, flushing, hypotension,
nausea/vomiting, rash, tachycardia, and respiratory distress.
Intravenous nitroglycerin combined with intravenous NAC may cause
symptomatic hypotension.
Fatalities have occurred from intravenous overdosage of NAC.
Oral NAC treatment, for acetaminophen poisoning, is contraindicated
in the presence of coma or vomiting or if activated charcoal has
been given by mouth.
Individuals with cystinuria should avoid, or limit, their intake
of cysteine supplements.
D-cysteine, D-cystine and 5-methyl cysteine are toxic forms that
should not be used.
Dosage Ranges and Duration of Administration:
- Acetaminophen poisoning: The typical oral dosage of NAC is 140
mg/kg body weight, followed four hours later by 70 mg/kg every
four hours for an additional 17 doses. Oral treatment must be
started within eight hours of an acetaminophen overdose to prevent
hepatoxicity. Oral NAC is typically administered for 72 hours;
intravenous NAC for 20 to 52 hours. It is recommended to give
the intravenous loading dose over 60 minutes, instead of 15 minutes,
to reduce the risk of adverse reactions.
- Bronchial disease: 200 mg bid
- HDL cholesterol: 1,200 to 3,600 mg per day
- Antioxidant protection/general health: 500 mg/day to start.
Individuals may increase the dose to 3 to 4 g/day as tolerated.
INTERACTIONS
Angiotensin-Converting Enzyme (ACE) Inhibitors
N-Acetylcysteine (NAC) may potentiate the antihypertensive effect
of ACE inhibitors via a nitric oxide-dependent mechanism (Suárez
et al. 1995). NAC (1200 mg/day) potentiated the reduction in systolic
and diastolic blood pressure induced by lisinopril (10 to 30 mg/day)
in six patients with essential hypertension. In spontaneously hypertensive
rats, NAC (300 mg/kg IV) potentiated the blood-pressure lowering
effects of captopril and enalaprilat (Ruiz et al. 1994).
Azathioprine; Cyclophosphamide; Predinisolone; Prednisone
Treatment with NAC infusions (4 to 10 d/day) combined with prednisone
(1 mg/kg) reversed cholestatic jaundice and pure red cell aplasia
in a patient receiving gold sodium thiomalate (160 mg IM) for progressive
psoriatic arthritis (Hansen et al. 1991). It is not known if these
effects were attributable to NAC combined with prednisone or NAC
therapy alone.
Adjunctive treatment with high dose NAC (600 mg po tid) in patients
on maintenance immunosuppressive therapy for fibrosing alveolitis
positively affected clinical course and pulmonary function (Behr
et al. 1997). These findings may warrant further investigation in
controlled clinical trials.
Cisplatin; Doxorubicin
In one in vitro study, NAC (1 mM) significantly inhibited cisplatin-induced
reactive oxygen species, an indicator of cytotoxicity, in bladder
cancer cells (Miyajima et al. 1999). The reduction was attributed
to the ability of NAC to enhance glutathione levels.
In vitro and in vivo studies have established that NAC protects
against doxorubicin-induced cardiotoxicity (D'Agostini et al. 1998;
Doroshow et al. 1981). NAC interacted synergistically with doxorubicin
to prevent tumorigenicity, metastasis, and alopecia in mice (D'Agostini
et al. 1998). In addition, NAC, alone and in combination with doxorubicin,
enhanced survival in mice injected with melanoma cells (D'Agostini
et al. 1998; De Flora et al. 1996). Clinical trials are needed to
confirm these effects in humans.
Isosorbide Mononitrate; Nitroglycerin
In vitro, NAC potentiated the antiplatelet effects of nitroglycerin
(Chirkov and Horowitz 1996).
Clinically, the combination of NAC (bolus dose of 2 g) and nitroglycerin
(1.5 µg/kg/min) prolonged vasodilation and minimized the development
of tolerance in patients with angina pectoris and normal left ventricular
function (Pizzulli, et al. 1997). Positive results were also obtained
in a double blind, placebo-controlled study of 200 patients with
unstable angina taking transdermal nitroglycerin either alone or
in combination with NAC; the combination of NAC and nitroglycerin
resulted in fewer deaths and myocardial infarctions (Ardissino et
al. 1997). In another randomized, double blind, placebo-controlled
study, NAC (2400 mg bid) potentiated the effects of isosorbide-5-mononitrate
(60 mg po) and increased exercise capacity in 10 patients with angina
pectoris, both without nitrate tolerance (Svendsen et al. 1989).
Although NAC may prevent nitrate tolerance, the high incidence of
side effects, particularly intolerable headache, may preclude its
clinical use (Ardissino et al. 1997; Iversen 1992).
Oxiconazole
In one study, topical application of NAC (15% w/v lotion) and oxiconazole
prolonged the mean residence time of oxiconazole in the upper nail
layers (51 to 100 mm) by as much as 73% (van Hoogdalem et al. 1997).
NAC may increase binding of oxiconazole to nails. |
