Acetylcysteine (N-acetylcysteine)
Acetylcysteine replenishes glutathione and is an important antidote in paracetamol poisoning. It also has mucolytic and antioxidant actions.
Oral/inhalation solutions and injectable concentrates are distinct products. A solution labeled for inhalation or oral use must not be treated as an injectable preparation.
For antidotal treatment, monitor hepatic enzymes, CBC and methemoglobin, plus electrolytes and hydration. Persistent hepatic or oxidative injury can require a longer treatment course than the initial schedule.
Nursing-animal data are limited. Lack of teratogenicity in laboratory studies does not establish reproductive safety in every veterinary species.
For phenol poisoning, the described loading treatment is followed by 50 mg/kg every 4 hours for 3 days; the maintenance route is not explicitly specified in that regimen.
After the loading treatment for xylitol-associated hepatic injury, 70 mg/kg four times daily has been described; the maintenance route is not explicitly specified in that protocol.
Group
Glutathione precursor; antidote; mucolytic; antioxidant
Mechanism of Action
Sulfhydryl donation supports glutathione synthesis and detoxification of reactive metabolites. Cleavage of mucus disulfide bonds lowers secretion viscosity.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Paracetamol toxicosis — Loading | 140 mg/kg | IV | Once | Begin promptly. For IV use, select an injectable product, dilute to 5% and administer slowly. A slow infusion over 15-20 minutes is described. |
| Paracetamol toxicosis — Loading | 140 mg/kg | PO | Once | Begin promptly; dilute the oral concentrate for tolerability. |
| Paracetamol toxicosis — Maintenance | 70 mg/kg | PO | Every 6 h | Give 5-7 further treatments; reassess liver injury and oxidative blood changes before stopping. |
| Contrast-associated nephropathy prophylaxis — Loading | 17 mg/kg | IV | Once | Reported prophylactic use; veterinary benefit is not established. |
| Contrast-associated nephropathy prophylaxis — Maintenance | 17 mg/kg | IV | Every 12 h | Up to 2 days; Reported follow-up regimen; veterinary benefit is not established. |
| Oxidative stress | 50 mg/kg | IV | Dilute in saline and infuse over one hour; this is an administered total, not an IV bolus or an unrestricted infusion rate. | |
| Phenol toxicosis — Loading | 140 mg/kg | PO | Once | Adjunct to supportive treatment; manage methemoglobinemia separately. |
| Phenol toxicosis — Loading | 140 mg/kg | IV | Once | Adjunct to supportive treatment; manage methemoglobinemia separately. Dilute and administer slowly for IV use. |
| Xylitol-associated hepatic injury — Loading | 140–280 mg/kg | PO | Once | Hepatoprotective adjunct; correct hypoglycemia and coagulopathy separately. Efficacy in limiting liver injury is uncertain. |
| Xylitol-associated hepatic injury — Loading | 140–280 mg/kg | IV | Once | Hepatoprotective adjunct; correct hypoglycemia and coagulopathy separately. Efficacy in limiting liver injury is uncertain. Dilute and infuse slowly. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Paracetamol toxicosis — Loading | 140 mg/kg | IV | Once | Begin promptly. For IV use, select an injectable product, dilute to 5% and administer slowly. A slow infusion over 15-20 minutes is described. |
| Paracetamol toxicosis — Loading | 140 mg/kg | PO | Once | Begin promptly; dilute the oral concentrate for tolerability. |
| Paracetamol toxicosis — Maintenance | 70 mg/kg | PO | Every 6 h | Give 5-7 further treatments; reassess liver injury and oxidative blood changes before stopping. |
| Contrast-associated nephropathy prophylaxis — Loading | 17 mg/kg | IV | Once | Reported prophylactic use; veterinary benefit is not established. |
| Contrast-associated nephropathy prophylaxis — Maintenance | 17 mg/kg | IV | Every 12 h | Up to 2 days; Reported follow-up regimen; veterinary benefit is not established. |
| Oxidative stress | 50 mg/kg | IV | Dilute in saline and infuse over one hour; this is an administered total, not an IV bolus or an unrestricted infusion rate. | |
| Phenol toxicosis — Loading | 140 mg/kg | PO | Once | Adjunct to supportive treatment; manage methemoglobinemia separately. |
| Phenol toxicosis — Loading | 140 mg/kg | IV | Once | Adjunct to supportive treatment; manage methemoglobinemia separately. Dilute and administer slowly for IV use. |
| Hepatic lipidosis — Loading | 140 mg/kg | IV | Once | Infuse over 20 minutes after dilution using an injectable product. Nutritional support is central to treatment; monitor refeeding-related electrolyte changes. |
| Hepatic lipidosis — Maintenance | 70 mg/kg | IV | Every 12 h | Dilute an injectable preparation and administer as an infusion; monitor potassium, phosphate and hepatic response. |
Indications
- Paracetamol toxicosis in dogs and cats.
- Topical ocular mucolysis.
- Selected antioxidant treatment protocols.
- Reported contrast-associated nephropathy prophylaxis; veterinary clinical benefit is uncertain.
- Ocular mucolysis in dogs and cats: apply a 2% ophthalmic acetylcysteine solution every 2 hours; an amount per application is not specified.
- Adjunctive treatment of phenol toxicosis.
- Hepatoprotective adjunct in canine xylitol poisoning; efficacy in preventing liver injury has not been established.
- Adjunctive treatment of feline hepatic lipidosis alongside nutritional therapy and correction of electrolyte deficits.
- Meconium retention in neonatal foals: a 4% retention enema can be prepared with 8 g acetylcysteine and 20 g sodium bicarbonate in 200 mL water. Administer 100-200 mL by gentle gravity flow and retain for 30-45 minutes; a repeat may be needed after 12 hours. This is a compounded rectal procedure, not an injectable or oral dose.
- Guttural-pouch chondroids in horses: local instillation of a 20% solution has been described; a delivered amount is not specified.
Contraindications
- Pulmonary use is contraindicated with known acetylcysteine hypersensitivity. For poisoning, balance prior reaction history against the need for a lifesaving antidote and manage infusion reactions promptly.
- Avoid nebulization in cats with airway disease because bronchoconstriction can worsen.
- Undiluted hyperosmolar concentrate is unsuitable for direct IV administration.
- Repeated enemas in foals can cause rectal mucosal irritation; persistent pain or distention after treatment requires reassessment for obstruction and possible surgery.
Interactions
- Compatibility with other drugs in a nebulizer or infusion is not established; do not mix without specific compatibility data.
- Activated charcoal can adsorb oral acetylcysteine. Separate oral administration by about 2-3 hours when feasible, but do not delay antidotal treatment; IV treatment can avoid this absorption problem.
- Reported physical incompatibilities include oxidizing agents, hydrogen peroxide, amphotericin B, ampicillin sodium, erythromycin lactobionate, tetracyclines and trypsin.
- Contact with reactive metals or rubber can affect solution stability; use suitable equipment and product-specific compatibility information.
Adverse effects
- Vomiting and gastrointestinal intolerance after oral administration.
- Anaphylactoid or hypersensitivity reactions, bronchospasm and hypotension during IV administration.
- Airway irritation or increased airway resistance with aerosol exposure in cats.
- Sensitization with prolonged topical use.
Toxicity
Rapid or concentrated IV administration can cause serious infusion reactions. Stop the infusion if a significant reaction develops and treat the reaction. During antidotal treatment monitor hepatic function, CBC and methemoglobin; tailor treatment length to the toxic exposure and laboratory response.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Acetadote 200 mg/mL Single-dose injectable concentrate; must be diluted before infusion. Discard unused opened-vial contents. | Injection | 200 mg / mL | IV |
| Acetylcysteine Solution USP 100 mg/mL Oral/inhalation product; not for injection. Avoid aerosol delivery in cats with airway disease. | Oral Liquid | 100 mg / mL | PO, INHALATION |
| Acetylcysteine Solution USP 200 mg/mL Oral/inhalation product; not for injection. Avoid aerosol delivery in cats with airway disease. | Oral Liquid | 200 mg / mL | PO, INHALATION |
| Mucinac 600 Tablets Acetylcysteine oral product; not an injectable preparation. | Tablet | 600 mg / tablet | PO |
