NACSYS Uses, Dosage, Side Effects, Food Interaction and all others data.

NACSYS has a mucolytic activity through its free sulfhydryl group. It acts directly on the mucoproteins to open the disulfide bonds and thus lowers the viscosity of the mucous and facilitates its removal by the muco-cillary action and expectoration. NACSYS improves the phagocytic capacity of the alveolar macrophages, thus protecting lungs from a variety of insults. NACSYS is a precursor to glutathione, the most important intra & extra-cellular antioxidant (the safest & most convenient)

NACSYS is indicated for mucolytic therapy and in the management of acetaminophen overdose. It has a short duration of action as it is given every 1-8 hours depending on route of administration, and has a wide therapeutic window. Patients should be counselled regarding diluting oral solutions in cola for taste masking, the risk of hypersensitivity, and the risk of upper gastrointestinal hemorrhage.

Trade Name NACSYS
Availability Rx and/or OTC
Generic Acetylcysteine
Acetylcysteine Other Names (R)-mercapturic acid, Acetilcisteina, Acetylcysteine, Acetylcysteinum, L-acetylcysteine, Mercapturic acid, N-acetylcysteine
Related Drugs biotin, Vitamin C, ascorbic acid, multivitamin, Zinc, Fish Oil, Mucinex DM, Robitussin Cough + Chest Congestion DM, dextromethorphan / guaifenesin, Tussin DM
Formula C5H9NO3S
Weight Average: 163.195
Monoisotopic: 163.030313849
Protein binding

Acetylcysteine is 66-97% protein bound in serum, usually to albumin.

Groups Approved, Investigational
Therapeutic Class Antidote preparations, Cough expectorants & mucolytics
Manufacturer Alturix Limited
Available Country United Kingdom
Last Updated: September 19, 2023 at 7:00 am


NACSYS is used for an adjunctive treatment for patients with abnormal, viscid or inspissated mucus secretions associated with conditions such as-

Acute and chronic bronchopulmonary disorders (e.g. pneumonia, bronchitis, emphysema, tracheobronchitis, chronic asthmatic bronchitis, tuberculosis, bronchiectasis, primary amyloidosis of the lung) Atelectasis caused by mucus obstruction Pulmonary complications of cystic fibrosis Pulmonary complications of thoracic and cardiovascular surgery Post-traumatic chest conditions.

It is effective in all respiratory airways disease causing formation of a dense secretion that cannot be or can only partially be expectorated such as acute and chronic bronchitis, laryngitis, sinusitis, tracheitis, infuenza & bronchial asthma. NACSYS is also used for the treatment of Paracetamol overdose. Treatment option is optimal if given within 8 hours of Paracetamol ingestion.

NACSYS is also used to associated treatment for these conditions: Acetaminophen Overdose, Chronic Rhinitis, Corneal Diseases, Corneal ulceration, Crusting Rhinitis, Keratopathy, Rhinitis, Sinusitis, Vasomotor Rhinitis, Acute Rhinitis, Subacute Rhinitis, Airway secretion clearance therapy

How NACSYS works

A number of possible mechanisms for the mucolytic activity of acetylcysteine have been proposed. NACSYS's sulfhydryl groups may hydrolize disulfide bonds within mucin, breaking down the oligomers, and making the mucin less viscous. NACSYS has also been shown to reduce mucin secretion in rat models. It is an antioxidant in its own right but is also deacetylated to cysteine, which participates in the synthesis of the antioxidant glutathione. The antioxidant activity may also alter intracellular redox reactions, decreasing phosphorylation of EGFR and MAPK, which decrease transcription of the gene MUC5AC which produces mucin.

In the case of acetaminophen overdoses, a portion of the drug is metabolized by CYP2E1 to form the potentially toxic metabolite N-acetyl-p-benzoquinone imine (NAPQI). The amount of NAPQI produced in an overdose saturates and depletes glutathione stores. The free NAPQI promiscuously binds to proteins in hepatocytes, leading to cellular necrosis. NACSYS can directly conjugate NAPQI or provide cysteine for glutathione production and NAPQI conjugation.


NACSYS dosage

NACSYS Tablet:

The dispersible tablet should be dissolved in 1/2 glass of water before use (preferably in the evening). The duration of treatment should be 5 to 10 days in the acute phase. It may be continued in the chronic state for up to 6 months or according to the advice of the physician.

As a mucolytic:

  • Adults: 600 mg daily as a single dose.
  • In Paracetamol overdose: Initially 140 mg/kg, followed by 70 mg/kg every 4 hours for an additional 17 doses. As an antidote, NACSYS is reported to be very effective when administered within 8 hours of Paracetamol overdose, with the protective effect diminishing after this time. Initiation of treatment after a lapse of 15 hours has previously been thought to be ineffective, but recent studies suggest that beneficial results may still be obtained.

NACSYS Respirator Solution:

The 20% solution may be diluted to a lesser concentration with either Sodium Chloride for injection, Sodium Chloride for inhalation, sterile water for injection, or sterile water for inhalation.

As a mucolytic:


  • 5-10 ml of 10% or 20% solution by nebulizer every 6-8 hr PRN.


  • 1-11 months: 1-2 ml of 20% or 2-4 ml of 10% solution by nebulizer every 6-8 hr PRN.
  • 12 months-11 years: 3-5 ml of 20% or 6-10 ml of 10% solution by nebulizer every 6-8 hr PRN.
  • Below 12 years: 5-10 ml of 10/20% solution by nebulizer every 6-8 hr PRN.

Diagnostic Bronchograms: 1-2 ml of 20% or 2-4 ml of 10% solution 2-3 times by nebulization or by instillation intratracheally prior to procedure.

Nebulization tent or croupette: This form of administration requires very large volumes of the solution, occasionally as much as 300 ml during a single treatment period. If a tent or croupette must be used, the recommended dose is the volume of acetylcysteine (using 20%) that will maintain a very heavy mist in the tent or croupette for the desired period. Administration for intermittent or continuous prolonged periods, including overnight, may be desirable.

Direct Instillation: When used by direct instillation, 1-2 ml of a 20% solution may be given as often as every hour. When used for the routine nursing care of patients with tracheostomy, 1-2 ml of a 20% solution may be given every 1-4 hours by instillation into the tracheostomy.

Side Effects

Generally, NACSYS is well tolerated. However, mild effects such as nausea, headache, tinnitus, urticaria, stomatitis, rhinorrhoea, chills, fever, bronchospasm may be observed. Occasional cases of nausea and dyspepsia, rare cases of urticaria may be observed.


Patients experiencing an overdose may present with vomiting, nausea, bronchospasm, periorbital angioedema, and hypotension. Treat patients with symptomatic and supportive measures. Hemodialysis may remove some acetylcysteine from circulation as it is somewhat protein bound.


NACSYS should be given in caution in asthma patients.


After taking NACSYS orally it increases the bioavailability of Amoxicillin, but shows no effect on Doxycycline and reduces the absorption of Cefalexin. NACSYS seems to increase the effects of Nitroglycerin.

Food Interaction

No interactions found.

Volume of Distribution

The volume of distribution of acetylcysteine is 0.47 L/kg.

Elimination Route

An 11 g dose in the form of an effervescent tablet for solution reaches a mean Cmax of 26.5 µg/mL, with a Tmax of 2 hours, and an AUC of 186 µg*h/mL.

Half Life

The mean terminal half life of acetylcysteine in adults is 5.6 hours and in pre-term neonates is 11 hours.


NACSYS has a mean clearance of 0.11 L/hr/kg.

Elimination Route

An oral dose of radiolabelled acetylcysteine is 13-38% recovered in the urine in the first 24 hours, while 3% is recovered in the feces.

Pregnancy & Breastfeeding use

Pregnancy Category B. Caution should be taken in case of pregnancy & lactation while using NACSYS.


Known hypersensitivity to active ingredient. Also contraindicated in patients suffering from phenylketonuria and peptic ulcer.

Acute Overdose

Accidental overdose of NACSYS may cause nausea, vomiting or diarrhea.

Storage Condition

Protect from light & moisture, store below 25° C. Keep all medicines out of the reach of children.

Innovators Monograph

You find simplified version here NACSYS

NACSYS contains Acetylcysteine see full prescribing information from innovator NACSYS Monograph, NACSYS MSDS, NACSYS FDA label


What is NACSYS?

NACSYS (Acetylcysteine) also known as N-acetylcysteine (NAC), is a medication that is used to treat paracetamol (acetaminophen) overdose, and to loosen thick mucus in individuals with chronic bronchopulmonary disorders like pneumonia and bronchitis. It can be taken intravenously, by mouth, or inhaled as a mist.

What is NACSYS used for?

NACSYS inhalation is used along with other treatments to relieve chest congestion due to thick or abnormal mucous secretions in people with lung conditions including asthma, emphysema, bronchitis and cystic fibrosis (an inborn disease that causes problems with breathing, digestion, and reproduction).

What are the side effects of NACSYS?

NACSYS is Likely safe for most adults. It can cause nausea, vomiting, and diarrhea or constipation. Rarely, it can cause rashes, fever, headache, drowsiness, low blood pressure, and liver problems.

Who should not take NACSYS?

If you have asthma or bleeding problems, your doctor may tell you to avoid NACSYS. You will likely be told to stop NACSYS 2 weeks before any elective surgery. If you're pregnant or breastfeeding, you must check with a doctor before using NACSYS supplements.

How long does NACSYS take to work?

The study showed that NACSYS significantly reduced the symptoms of trichotillomania compared to a placebo. 56% of subjects reported "much or very much improved" on NACSYS compared to 16% on placebo (sugar pill or inert substance). Significant improvement was initially noted after 9 weeks of treatment.

When is the best time to take NACSYS?

Single amino acid supplements, like NACSYS, are best taken on an empty stomach. The absorption of amino acids can be affected by the foods you take them with and by other amino acids.

Is NACSYS safe to take daily?

There is no recommended daily allowance for NACSYS, because unlike vitamins, it's not an essential nutrient. The dosage used to prevent radio contrast dye damage is 600 mg to 1200 mg every 12 hours for 48 hours.

What are the benefits of taking NACSYS?

Classic mucolytic drugs such as NACSYS decrease the viscoelastic properties of mucus by reducing disulfide bonds. In contrast, expectorants change mucus consistency and make coughing more productive, mucokinetics improve transportability, and mucoregulators suppress mucus secretion.

Does NACSYS really work?

NACSYS supplements have been used to improve COPD symptoms, exacerbations and lung decline. In a one-year study, 600 mg of NACSYS twice a day significantly improved lung function and symptoms in those with stable COPD. Those with chronic bronchitis can also benefit from NACSYS.

Is NACSYS safe in pregnancy?

Animal studies did not show teratogenicity; slightly decreased fertility was seen at doses above the maximum human dose. Limited case reports did not report any adverse fetal or neonatal outcomes. This drug crosses the placenta and was measurable in the serum of the infant. Pregnant women should be managed the same way as nonpregnant patients for acetaminophen overdose, and that acetylcysteine therapy was protective to both mother and fetus. There are no controlled data in human pregnancy. Use is not recommended unless clearly needed.

Is NACSYS safe during Breastfeeding?

Animal studies did not show adverse effects during lactation. It is unknown in this drug or its metabolites are excreted in milk. Based on the pharmacokinetics, it should be nearly cleared 30 hours after administration. Use is not recommended.

*** Taking medicines without doctor's advice can cause long-term problems.