N-acetylcysteine

N-acetylcysteine

a mucolytic agent used to reduce the viscosity of secretions of the respiratory tract. The principal method of administration is by aerosol, which in animals requires the use of a face mask or aerosol chamber. Also used parenterally in the treatment of acetaminophen poisoning in cats where it aids in detoxification of the drug and enhances its elimination, and topically in the treatment of collagenase-associated corneal ulcers.

---

acetylcysteine (N-acetylcysteine)

Acetadote, Mucomyst (CA), Mucomyst 10, Mucosil-10, Mucosil-20, Parovelex (UK) (CA)

Pharmacologic class: N-acetyl derivative of naturally occurring amino acid (L-cysteine)

Therapeutic class: Mucolytic, acetaminophen antidote

Pregnancy risk category B

Action

Decreases viscosity of secretions, promoting secretion removal through coughing, postural drainage, and mechanical means. In acetaminophen overdose, maintains and restores hepatic glutathione, needed to inactivate toxic metabolites.

Availability

Injection: 200 mg/ml

Solution: 10%, 20%

⊘Indications and dosages

➣ Mucolytic agent in adjunctive treatment of acute and chronic bronchopulmonary disease (bronchitis, bronchiectasis, chronic asthmatic bronchitis, emphysema, pneumonia, primary amyloidism of lungs, tuberculosis, tracheobronchitis), pulmonary complications of cystic fibrosis, atelectasis, or pulmonary complications related to surgery, posttraumatic chest conditions, tracheostomy care, or use during anesthesia

Adults and children: Nebulization (face mask, mouthpiece, tracheostomy) - 6 to 10 ml of 10% solution or 3 to 5 ml of 20% solution three or four times daily. Dosage range is 2 to 20 ml of 10% solution or 1 to 10 ml of 20% solution q 2 to 6 hours.

Nebulization (tent or croupette) - Volume of 10% or 20% solution that will maintain heavy mist for desired period

Instillation (direct) - 1 to 2 ml of 10% to 20% solution q 1 hour p.r.n.

Instillation via syringe attached to percutaneous intratracheal catheter - 2 to 4 ml of 10% solution or 1 to 2 ml of 20% solution q 1 to 4 hours

➣ Diagnostic bronchial studies

Adults and children: Two to three doses of 2 to 4 ml of 10% solution or 1 to 2 ml of 20% solution by nebulization or intratracheal instillation before procedure

➣ Acetaminophen overdose

Adults, elderly patients, children: Give immediately if 24 hours or less have elapsed since acetaminophen ingestion. Use the following protocol: Empty stomach by lavage or emesis induction, and then have patient drink copious amounts of water. If activated charcoal has been given, perform lavage before giving acetylcysteine. Draw blood for acetaminophen plasma assay and baseline aspartate aminotransferase (AST), alanine aminotransferase (ALT), prothrombin time, bilirubin, blood glucose, blood urea nitrogen, electrolyte, and creatinine clearance levels. If ingested acetaminophen dose is in toxic range, give acetylcysteine 140 mg/kg P.O. as loading dose from 20% solution. Administer 17 maintenance doses of 70 mg/kg P.O. q 4 hours, starting 4 hours after loading dose. Repeat procedure until acetaminophen blood level is safe. If patient vomits loading dose or any maintenance dose within 1 hour of administration, repeat that dose.

Off-label uses

• Unstable angina

Contraindications

• Hypersensitivity to drug (except with antidotal use)
• Status asthmaticus (except with antidotal use)

Precautions

Use cautiously in:
• renal or hepatic disease, Addison's disease, alcoholism, brain tumor, bronchial asthma, seizure disorder, hypothyroidism, respiratory insufficiency, psychosis
• elderly patients
• pregnant or breastfeeding patients.

Administration

• Separate administration times of this drug and antibiotics.
• Use plastic, glass, or stainless steel container when giving by nebulizer, because solution discolors on contact with rubber and some metals.
• Once solution is exposed to air, use within 96 hours.
• Dilute solution before administering for acetaminophen overdose, to reduce risk of vomiting and reduce drug's unpleasant odor and irritating or sclerosing properties.
• Chill solution and have patient sip through straw, or, if necessary, give by nasogastric tube when administering for acetaminophen overdose.

Route	Onset	Peak	Duration
P.O.	30-60 min	1-2 hr	Unknown
Instillation, inhalation	1 min	5-10 min	2-3 hr

Adverse reactions

CNS: dizziness, drowsiness, headache

CV: hypotension, hypertension, tachycardia

EENT: severe rhinorrhea

GI: nausea, vomiting, stomatitis, constipation, anorexia

Hepatic: hepatotoxicity

Respiratory: hemoptysis, tracheal and bronchial irritation, increased secretions, wheezing, chest tightness, bronchospasm

Skin: urticaria, rash, clamminess, angioedema

Other: tooth damage, chills, fever, hypersensitivity including anaphylaxis

Interactions

Drug-drug. Activated charcoal: increased absorption and decreased efficacy of acetylcysteine

Nitroglycerin: increased nitroglycerin effects, causing hypotension and headache

Drug-diagnostic tests. Liver function tests: abnormal results

Patient monitoring

• Monitor respirations, cough, and character of secretions.

Patient teaching

• Instruct patient to report worsening cough and other respiratory symptoms.
• Advise patient to mix oral form with juice or cola to mask bad taste and odor.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.