Vetdrugs 2.0Acetylcysteine, or N-acetylcysteine, is a sulfhydryl-containing drug with two distinct veterinary roles: replenishing antioxidant defenses and reducing the viscosity of mucus or inspissated material. It is an important antidote for paracetamol poisoning in dogs and cats and is also used as an adjunct in selected hepatotoxic or oxidative disorders.
Local mucolytic uses include ophthalmic treatment and specific equine procedures involving retained meconium or guttural-pouch chondroids. The strength of evidence varies across its many proposed antioxidant applications; a plausible biochemical effect does not establish benefit in every clinical condition.
Group
Glutathione precursor; antidote; mucolytic; antioxidant
Mechanism of Action
Acetylcysteine supplies cysteine for synthesis of glutathione, a major intracellular antioxidant. Restoring glutathione helps hepatocytes conjugate and detoxify reactive paracetamol metabolites before they bind cellular proteins. Sulfhydryl donation and reducing activity also support management of associated oxidative injury; early antidotal treatment is more effective than waiting for established hepatic damage.
The free sulfhydryl group reduces disulfide bonds linking mucin molecules. Breaking these cross-links decreases the viscosity and tenacity of secretions, which can facilitate clearance from local sites. This chemical effect explains its use for thick ocular mucus, retained meconium and some chondroid material, without implying dissolution of all obstructive tissue.
Topical ophthalmic activity also includes inhibition of proteolytic processes associated with corneal melting. This local antiproteolytic action complements the reduction of mucus viscosity at the ocular surface.
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. |
| Paracetamol toxicosis — Maintenance | 70 mg/kg | IV | Every 4 h | Distinct five-treatment maintenance course after a 140 mg/kg loading dose. Use an injectable formulation, dilute and administer slowly; do not mix the interval and treatment count with a different protocol. |
| Ocular mucolysis | Reference only | TOPICAL | Topical 2% solution every two hours is described. This is a local concentration, not a systemic dose; ocular suitability and preparation technique matter. | |
| Paracetamol toxicosis — Loading | 150 mg/kg | PO, IV | Alternative protocol: loading treatment followed by 50 mg/kg every four hours for 17 further treatments. The excerpt does not independently confirm the maintenance route; do not assume it from the loading route. IV use requires dilution and slow administration. | |
| Degenerative myelopathy | 25 mg/kg | PO | Every 8 h | Combination protocol: 25 mg/kg every eight hours for two weeks, then every eight hours on alternate days, with aminocaproic acid 500 mg/dog PO every eight hours. No treatment has demonstrated efficacy in published trials in the source account. Dilute 20% solution to 5% in a suitable oral diluent. |
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. |
| Paracetamol toxicosis — Maintenance | 70 mg/kg | IV | Every 4 h | Distinct five-treatment maintenance course after a 140 mg/kg loading dose. Use an injectable formulation, dilute and administer slowly; do not mix the interval and treatment count with a different protocol. |
| Ocular mucolysis | Reference only | TOPICAL | Topical 2% solution every two hours is described. This is a local concentration, not a systemic dose; ocular suitability and preparation technique matter. |
Horses
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Guttural-pouch chondroids | Reference only | TOPICAL | Local instillation of a 20% solution is described to loosen chondroids. Instilled volume and frequency are not supplied; this is not a systemic-dose calculation. | |
| Meconium retention in foals | Reference only | RECTAL | Retention-enema alternatives: 8 g acetylcysteine with 20 g sodium bicarbonate in 200 mL water, pH about 7.6; or slow gravity administration of 100–200 mL of a 4% solution with retention for 30–45 minutes. The latter description uses a 30 French Foley catheter with a 30 mL balloon. Provide fluids and analgesia when indicated and monitor bladder distention. Repeated enemas may irritate the rectum; reassess persistent obstruction. |
Indications
- Antidotal treatment of paracetamol toxicosis in dogs and cats, replenishing glutathione and limiting reactive-metabolite injury.
- Topical ocular mucolysis and adjunctive treatment of protease-associated corneal melting in dogs and cats.
- Adjunctive antioxidant treatment of phenol toxicosis and selected hepatotoxic conditions.
- Adjunctive hepatoprotective treatment in canine xylitol poisoning; prevention of liver injury has not been established.
- Adjunctive antioxidant support in feline hepatic lipidosis alongside nutritional treatment.
- Local mucolytic treatment of retained meconium in neonatal foals and inspissated chondroid material in equine guttural pouches.
- Investigational prevention of contrast-associated nephropathy; veterinary clinical benefit remains uncertain.
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 |
| Mucinac 200 Tablets Cipla Limited Confirm the product-specific method of dispersion before administration; no equal-dose tablet divisions are established here. | Tablet | 200 mg / tablet | PO |
Monitoring and Administration
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.
A staged IV oxidative-stress protocol gives 150 mg/kg over 60 minutes, then 50 mg/kg over four hours, then 100 mg/kg over sixteen hours. Preserve the three stages and their durations; this is not an unrestricted bolus or simple continuous rate.
Protect acetylcysteine from light and air because oxidation reduces stability. A light-purple color may occur without loss of quality in the described product. One supplied formulation instruction permits 24 hours at room temperature after dilution; do not transfer that period to all products.