Acetylcysteine (N-acetylcysteine, Mucomyst, NAC)

By | 2013-06-07

Antidote; Mucolytic

Highlights Of Prescribing Information

Used primarily as a treatment for acetaminophen or phenol toxicity & for its mucolytic effect; used anecdotally for treating degenerative myelopathy

Also used as a topical ophthalmic ()

Has caused hypersensitivity & bronchospasm when used in pulmonary tree

Administer via gastric- or duodenal tube for acetaminophen poisoning in animals

What Is Acetylcysteine Used For?

Acetylcysteine is used in veterinary medicine as both a mucolytic agent in the pulmonary tree and as a treatment for acetaminophen or phenol toxicity in small animals. It has been used anecdotally with aminocaproic acid to treat degenerative myelopathy in dogs.

In horses with strangles, acetylcysteine instilled into the gutteral pouch has been used to help break up chondroids and avoid the need for surgical removal. Acetylcysteine enemas have been used in neonatal foals to break up meconium refractory to repeated enemas.

Before you take Acetylcysteine

Contraindications / Precautions / Warnings

Acetylcysteine is contraindicated (for pulmonary indications) in animals hypersensitive to it. There are no contraindications for its use as an antidote.

Because acetylcysteine may cause bronchospasm in some patients when used in the pulmonary system, animals with bronchospastic diseases should be monitored carefully when using this agent.

Adverse Effects

When given orally for acetaminophen toxicity, acetylcysteine can cause GI effects (nausea, vomiting) and rarely, urticaria. Because the taste of the solution is very bad, use of taste masking agents {e.g., colas, juices) have been used. Since oral dosing of these drugs may be very difficult in animals, gastric or duodenal tubes may be necessary.

Rare adverse effects reported when acetylcysteine is administered into the pulmonary tract, include: hypersensitivity, chest tightness, bronchoconstriction, and bronchial or tracheal irritation.

Overdosage / Acute Toxicity

The LD50 of acetylcysteine in dogs is 1 g/kg (PO) and 700 mg/kg (IV). It is believed that acetylcysteine is quite safe (with the exception of the adverse effects listed above) in most overdose situations.

How to use Acetylcysteine

Acetylcysteine dosage for dogs:

For acetaminophen toxicity:

a) A 2-3 hour wait between activated charcoal and PO administration of acetylcysteine (NAC) is necessary. Give NAC as an initial oral loading dose of 140 mg/kg (dilute to 5% in dextrose or sterile water), followed by 70 mg/kg PO four times daily (q6h) for 7 treatments. With ingestion of massive quantities, some authors suggest using a 280 mg/kg loading dose and continuing treatment for 12-17 doses. May also be given IV after diluting to 5% and given via slow IV over 15-20 minutes. Additional therapy may include IV fluids, blood or Oxyglobin, ascorbic acid and SAMe. ()

b) 150 mg/kg PO or IV initially, then 50 mg/kg q4h for 17 additional doses ()

c) Loading dose of 140 mg/kg PO, then 70 mg/kg PO every 6 hours for 7 treatments ()

For phenol toxicity:

a) 140 mg/kg PO or IV initially, then 50 mg/kg q4h for 3 days. May be partially effective to reduce hepatic and renal injury. Resultant methemoglobinemia should be treated with ascorbic acid or methylene blue. ()

For respiratory use:

a) 50 mL/hr for 30-60 minutes every 12 hours by nebulization ()

For degenerative myelopathy:

a) 25 mg/kg PO q8h for 2 weeks, then q8h every other day. The 20% solution should be diluted to 5% with chicken broth or suitable diluent. Used in conjunction with aminocaproic acid (500 mg per dog PO q8h indefinitely). Other treatments may include prednisone (0.25-0.5 mg/kg PO daily for 10 days then every other day), Vitamin C (1000 mg PO q12h) and Vitamin E (1000 Int. Units PO q12h). Note: No treatment has been shown to be effective in published trials. ()

Acetylcysteine dosage for cats:

For acetaminophen toxicity:

a) A 2-3 hour wait between activated charcoal and PO administration of acetylcysteine (NAC) is necessary. Give NAC as an initial oral loading dose of 140 mg/kg (dilute to 5% in dextrose or sterile water), followed by 70 mg/kg PO four times daily (q6h) for 7 treatments. With ingestion of massive quantities, some authors suggest using a 280 mg/kg loading dose and continuing treatment for 12-17 doses. May also be given IV after diluting to 5% and given via slow IV over 15-20 minutes. Additional therapy may include IV fluids, blood or Oxyglobin9, ascorbic acid and SAMe. ()

b) 150 mg/kg PO or IV initially, then 50 mg/kg q4h for 17 additional doses ()

For phenol toxicity:

a) 140 mg/kg PO or IV initially, then 50 mg/kg q4h for 3 days. May be partially effective to reduce hepatic and renal injury. Resultant methemoglobinemia should be treated with ascorbic acid or methylene blue. ()

For respiratory use:

a) 50 mL/hr for 30-60 minutes every 12 hours by nebulization ()

For adjunctive treatment of hepatic lipidosis (see also Carnitine):

a) Identify underlying cause of anorexia and provide a protein replete feline diet, give acetylcysteine (NAC) at 140 mg/kg IV over 20 minutes, then 70 mg/kg IV q12h; dilute 10% NAC with saline 1:4 and administer IV using a 0.25 micron filter; correct hypokalemia and hypophosphatemia, beware of electrolyte changes with re-feeding phenomenon ()

Acetylcysteine dosage for horses:

To help break up chondroids in the gutteral pouch:

a) Instill 20% solution ()

In neonatal foals to break up meconium refractory to repeated enemas:

a) 8 grams in 20 g sodium bicarbonate in 200 mL water (pH of 7.6), give as enema as needed to effect ()

b) With foal in lateral recumbency, insert a 30 french foley catheter with a 30 cc bulb for a retention enema. Using gravity flow, infuse slowly 100-200 mL of 4% acetylcysteine solution and retain for 30-45 minutes. IV fluids and pain medication should be considered. Monitor for possible bladder distention. ()

Monitoring

When used for acetaminophen poisoning:

■ Hepatic enzymes (particularly in dogs)

■ Acetaminophen level, if available (particularly in dogs)

■ Hemogram, with methemoglobin value (particularly in cats)

■ Serum electrolytes, hydration status

Client Information

■ This agent should be used in a clinically supervised setting only

Chemistry / Synonyms

The N-acetyl derivative of L-cysteine, acetylcysteine occurs as a white, crystalline powder with a slight acetic odor. It is freely soluble in water or alcohol.

Acetylcysteine may also be known as: N-acetylcysteine or N-acetyl-L-cysteine, NAC, 5052 acetylcysteinum, NSC-111180, Acetadote, Mucomyst or ACC.

Storage / Stability/Compatibility

When unopened, vials of sodium acetylcysteine should be stored at room temperature (15-30°C). After opening, vials should be kept refrigerated and used within 96 hours. The product labeled for IV use states to use within 24 hours.

Acetylcysteine is incompatible with oxidizing agents; solutions can become discolored and liberate hydrogen sulfide when exposed to rubber, copper, iron, and during autoclaving. It does not react to aluminum, stainless steel, glass or plastic. If the solution becomes light purple in color, potency is not appreciably affected, but it is best to use non-reactive materials when giving the drug via nebulization. Acetylcysteine solutions are incompatible with amphotericin B, ampicillin sodium, erythromycin lactobionate, tetracycline, oxytetracycline, iodized oil, hydrogen peroxide and trypsin.

Dosage Forms / Regulatory Status

Veterinary-Labeled Products: None

Human-Labeled Products:

Acetylcysteine injection: 20% (200 mg/mL), (0.5 mg/mL EDTA in 30 mL single-dose vials, preservative free; Acetadote (Cumberland); (Rx)

Acetylcysteine Solution: 10% & 20% (as sodium) in 4 mL, 10 mL, 30 mL & 100 mL (20% only) vials; Mucomyst (Apothecon); (Rx) Note: If using this product for dilution and then intravenous dosing, it is preferable to use a 0.2 micron in-line filter.