乙酰半胱氨酸-Acetylcysteine

Acetylcysteine

Acetylcysteine is the N-acetyl derivative of L-cysteine, appearing as a white crystalline powder with a slightly acidic taste. It is readily soluble in water or ethanol.

⸻

Storage

Unopened sodium acetylcysteine should be stored at room temperature (15–30°C).

Once opened, it should be refrigerated and used within 96 hours.

Acetylcysteine should not be mixed with oxidizing agents. Its solution may discolor and release hydrogen sulfide when in contact with rubber, copper, or iron, or when autoclaved. However, it is stable with aluminum, stainless steel, glass, and plastic.

A light purple discoloration does not significantly affect potency, but for nebulization, use only equipment made from compatible materials.

Incompatible with: amphotericin B, ampicillin sodium, lactobionate erythromycin, tetracycline, oxytetracycline, iodized oil, hydrogen peroxide, and trypsin.

⸻

Pharmacology / Indications / Pharmacokinetics

When administered intratracheally, acetylcysteine reduces the viscosity of purulent and non-purulent secretions, promoting their clearance by coughing, suction, or postural drainage.

Its free sulfhydryl group breaks disulfide bonds in mucoproteins—an effect most pronounced at pH 7–9. It has no effect on living tissue or fibrin clots.

Acetylcysteine can also protect against hepatic injury and methemoglobinemia caused by acetaminophen (paracetamol) toxicity by providing an alternative substrate that binds toxic metabolites and restores glutathione levels.

In veterinary medicine, acetylcysteine is used as a mucolytic agent for respiratory and ocular conditions, and as an antidote for acetaminophen poisoning in small animals.

Infusion of acetylcysteine into esophageal diverticula in horses with strangles helps dissolve chondroids, avoiding surgical removal. Repeated rectal administration in newborn foals can help break down meconium impactions.

After oral administration, acetylcysteine is absorbed from the gastrointestinal tract.

Following nebulization or intratracheal administration, most of the drug participates in thiol–disulfide reactions in the lungs, while the remainder is absorbed and deacetylated in the liver to cysteine for further metabolism.

Contraindications:

•Hypersensitivity to acetylcysteine (for respiratory indications).

•None when used as an antidote.

Precautions:

Acetylcysteine may induce bronchospasm in some animals with respiratory disease; monitoring is advised when used in bronchospastic conditions.

⸻

Drug Safety

In dogs, the LD₅₀ of acetylcysteine is approximately 1 g/kg (oral) and 700 mg/kg (IV).

It is generally considered very safe even in overdose, aside from the adverse reactions mentioned above.

Although activated charcoal can adsorb acetylcysteine, its concurrent use in acetaminophen toxicity is debated. In humans, it is recommended to wait at least 3 hours between administration of activated charcoal and the first dose of acetylcysteine.

However, in cats, acetaminophen ingestion can quickly cause methemoglobinemia, so treatment with acetylcysteine should not be delayed.

⸻

Dosage

Dogs

For acetaminophen (paracetamol) toxicity:

•Initial dose: 150 mg/kg, then 50 mg/kg every 4 hours, orally or IV, for a total of 17 doses.

•Alternatively: Loading dose 140 mg/kg (5% solution), then 70 mg/kg every 4 hours, orally or IV, for 3–5 additional doses.

•Another regimen: Loading dose 140 mg/kg, followed by 70 mg/kg every 6 hours orally, for 7 doses.

For respiratory conditions:

•Nebulization: 50 mL/hour, administered every 12 hours for 30–60 minutes per session.

⸻

Source: Veterinary Drug Manual

Compiled and published by: Mao Pipipet Veterinary Team