MUCOMYST
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MUCOMYST (MUCOMYST).
Acetylcysteine reduces mucus viscosity by breaking disulfide bonds in mucoproteins, thereby facilitating mucus clearance. It also serves as a precursor to glutathione, providing antioxidant effects and hepatoprotection in acetaminophen overdose.
| Metabolism | Acetylcysteine is extensively metabolized in the liver via deacetylation to cysteine, which is further metabolized to glutathione, taurine, and inorganic sulfate. Minor pathways involve conjugation. |
| Excretion | Primarily renal as inactive metabolites (e.g., N-acetylcysteine, cysteine, inorganic sulfate). Less than 30% excreted unchanged in urine. Minor fecal elimination. |
| Half-life | Terminal elimination half-life is approximately 5.6 hours (range 5–6.5 h) in adults; prolonged in patients with hepatic impairment. For acetaminophen overdose, a second prolonged phase (>15 h) may occur. |
| Protein binding | 50-83% bound to albumin and other plasma proteins. Binding decreases with increasing N-acetylcysteine concentrations. |
| Volume of Distribution | 0.33–0.47 L/kg in adults (approximates total body water). Widely distributed, crossing placental barrier and present in breast milk. |
| Bioavailability | Oral: very low (6–10%) due to extensive first-pass metabolism. Intravenous: 100%. Inhalation: limited systemic absorption (<3% of dose). |
| Onset of Action | Intravenous: within 30 minutes for acetaminophen detoxification; oral: within 45–60 minutes for mucolysis peak effect; inhalation: 5–10 minutes for initial mucolysis. |
| Duration of Action | Intravenous: effects persist for 4–6 hours post-dose for glutathione repletion; oral: 4–8 hours; inhalation: 2–4 hours depending on mucus reduction. |
Acetaminophen overdose: 140 mg/kg orally as loading dose, then 70 mg/kg every 4 hours for 17 doses (total 1330 mg/kg). For inhalation: 3-5 mL of 20% solution via nebulization 3-4 times daily.
| Dosage form | SOLUTION |
| Renal impairment | No specific dose adjustment required; however, accumulation of metabolites may occur in severe renal impairment (CrCl <30 mL/min), use with caution. |
| Liver impairment | No specific dose adjustment for NAC; however, use caution in severe hepatic impairment (Child-Pugh C) as NAC may cause further hepatic injury. |
| Pediatric use | Acetaminophen overdose: Same loading dose 140 mg/kg orally, then 70 mg/kg every 4 hours for 17 doses. Inhalation: 3-5 mL of 20% solution nebulized 3-4 times daily; may use 10% solution if tolerated. |
| Geriatric use | No specific dose adjustment; use lowest effective dose and monitor for side effects due to age-related decline in organ function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MUCOMYST (MUCOMYST).
| Breastfeeding | Compatible with breastfeeding. M/P ratio not established; likely low excretion. Caution with high doses due to potential for sulfite sensitivity in infant. |
| Teratogenic Risk | FDA Pregnancy Category B. No evidence of teratogenicity in animal studies; inadequate human studies. Potential risk of methemoglobinemia in neonates if used near term. Avoid during third trimester unless clearly needed. |
| Fetal Monitoring |
■ FDA Black Box Warning
Anaphylactoid reactions, including severe bronchospasm, have been reported with acetylcysteine administration. Emergency equipment and medications for treating anaphylaxis must be readily available.
| Serious Effects |
Hypersensitivity to acetylcysteine or any component of the formulation.
| Precautions | May induce bronchospasm, especially in asthmatic patients. Use with caution in patients with a history of peptic ulcer disease. Solutions may contain sodium ions; monitor in sodium-restricted patients. Risk of fluid overload with excessive dosing. |
Loading safety data…
| Monitor for bronchospasm, nausea, vomiting in mother. In fetus/neonate: monitor for methemoglobinemia if high doses used near delivery. |
| Fertility Effects | No known adverse effects on fertility in animal studies. Human data lacking. |