MUCOMYST W/ ISOPROTERENOL
Clinical safety rating
cautionComprehensive clinical and safety monograph for MUCOMYST W/ ISOPROTERENOL (MUCOMYST W/ ISOPROTERENOL).
Acetylcysteine reduces mucous viscosity by cleaving disulfide bonds in mucoproteins, enhancing clearance of respiratory secretions. Isoproterenol is a non-selective beta-adrenergic agonist that stimulates beta-1 and beta-2 receptors, causing bronchodilation and increased mucociliary clearance.
| Metabolism | Acetylcysteine undergoes rapid deacetylation in the liver to cysteine and other metabolites; isoproterenol is metabolized by catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO). |
| Excretion | Acetylcysteine and isoproterenol are both extensively metabolized. Acetylcysteine is metabolized in the liver to cysteine and other metabolites; renal excretion of inorganic sulfate and unchanged drug accounts for less than 30% of the dose. Isoproterenol is rapidly metabolized by COMT and other pathways; less than 2% is excreted unchanged in urine. |
| Half-life | Acetylcysteine: terminal half-life is approximately 5.6 hours in adults (range 3-8 hours); increased in patients with hepatic impairment. Isoproterenol: half-life is approximately 2.5-5 minutes due to rapid hepatic and tissue metabolism. |
| Protein binding | Acetylcysteine: 50-83% bound to plasma proteins. Isoproterenol: approximately 65% bound to plasma proteins. |
| Volume of Distribution | Acetylcysteine: 0.33-0.47 L/kg, indicating distribution primarily into total body water. Isoproterenol: 0.5-1.0 L/kg, consistent with extensive tissue distribution. |
| Bioavailability | Inhalation: bioavailability of both components is variable and dose-dependent; systemic absorption of acetylcysteine is approximately 10-30%; isoproterenol's systemic bioavailability is less than 10% due to rapid metabolism in the lung and liver. |
| Onset of Action | Inhalation: acetylcysteine liquefies mucus within 1-3 minutes; isoproterenol produces bronchodilation within 1-5 minutes. |
| Duration of Action | Inhalation: acetylcysteine's mucolytic effect lasts 1-6 hours; isoproterenol's bronchodilator effect lasts 30-60 minutes. |
| Molecular Weight | 163.19 Da (acetylcysteine); 211.26 Da (isoproterenol) |
Acetylcysteine 10-20% solution 3-5 mL via nebulization with isoproterenol 0.5 mL (0.5 mg) q6-8h; isoproterenol dose adjusted to heart rate not exceeding 120/min.
| Dosage form | SOLUTION |
| Renal impairment | No specific dose adjustment required for acetylcysteine; isoproterenol clearance may decrease with severe renal impairment, use with caution. |
| Liver impairment | No specific dose adjustment required for acetylcysteine; isoproterenol metabolism may be impaired in severe hepatic disease, monitor response. |
| Pediatric use | Acetylcysteine 10-20% solution 1-3 mL via nebulization with isoproterenol 0.25-0.5 mg (0.25-0.5 mL) q6-8h, weight-based: 0.2-0.5 mL/kg per dose of acetylcysteine. |
| Geriatric use | Use lower end of dosing range due to increased sensitivity to isoproterenol; monitor heart rate and blood pressure; adjust isoproterenol dose to avoid tachycardia (>120/min). |
| 1st trimester | Mucolytic use is generally avoided in first trimester unless benefit outweighs risk; acetylcysteine is FDA pregnancy category B, isoproterenol is category C. Isoproterenol may cause fetal tachycardia and should be used with caution. |
| 2nd trimester | In second trimester, acetylcysteine is considered safe when needed; isoproterenol should be used cautiously as it can stimulate beta-adrenergic receptors potentially affecting uterine blood flow. |
| 3rd trimester | In third trimester, isoproterenol may inhibit uterine contractions and cause fetal tachycardia; acetylcysteine is safe. Use only if clearly needed. |
Clinical note
Comprehensive clinical and safety monograph for MUCOMYST W/ ISOPROTERENOL (MUCOMYST W/ ISOPROTERENOL).
| Placental transfer | Acetylcysteine crosses the placenta; isoproterenol is expected to cross due to low molecular weight but specific data are lacking. |
| Breastfeeding | Acetylcysteine is excreted into breast milk in small amounts, presumably safe. Isoproterenol is not known to be excreted into breast milk; however, due to its short half-life and poor oral bioavailability, exposure via breastfeeding is likely minimal. |
| Lactation Rating | L2 (Safer) |
| Teratogenic Risk | Acetylcysteine: No evidence of teratogenicity in animal studies; human data limited. Isoproterenol: Beta-agonist; theoretical risk of fetal tachycardia and hypoglycemia; no documented teratogenicity in humans. First trimester: No known increase in malformations. Second and third trimesters: May cause uterine relaxation and fetal tachycardia. Avoid near term due to potential for uterine atony and neonatal hypoglycemia. |
| Fetal Monitoring | Monitor maternal heart rate, blood pressure, and respiratory status. Fetal heart rate monitoring during prolonged use. Assess for signs of uterine relaxation or preterm labor. Neonatal monitoring for hypoglycemia and tachycardia if used near delivery. |
| Fertility Effects | Acetylcysteine: No known adverse effects on fertility. Isoproterenol: No specific data; beta-agonists may theoretically impair fertility through uterine relaxation or hormonal effects, but not documented. |
■ FDA Black Box Warning
Acute, potentially fatal bronchospasm has occurred with nebulized acetylcysteine, especially in asthmatic patients; isoproterenol is included to reduce this risk. Serious anaphylactoid reactions, including death, have been reported with intravenous acetylcysteine for acetaminophen overdose.
| Serious Effects |
Hypersensitivity to acetylcysteine or isoproterenolTachyarrhythmias (isoproterenol component)Angle-closure glaucoma (isoproterenol component)
| Precautions | May induce bronchospasm; discontinue use if bronchospasm worsens, Use caution in patients with asthma or history of bronchospasm, Isoproterenol may cause tachycardia, arrhythmias, and myocardial ischemia, Acetylcysteine may cause stomatitis, rhinorrhea, and nausea with nebulization, Possible sensitization to isoproterenol with prolonged use |
| Food/Dietary | None known for inhaled acetylcysteine or isoproterenol. |
| Clinical Pearls | Mucomyst (acetylcysteine) combined with isoproterenol is used as a mucolytic in inhalation therapy. Isoproterenol is a beta-adrenergic agonist that can cause tachycardia and arrhythmias. Monitor heart rate and ECG during administration. Acetylcysteine can cause bronchospasm; isoproterenol may mitigate this. Do not mix with other nebulized medications; use separate nebulizers. |
| Patient Advice | Use exactly as prescribed; do not adjust dose. · Report palpitations, chest pain, or difficulty breathing immediately. · Rinse mouth after inhalation to prevent throat irritation. · Do not use if solution is discolored or contains particles. · Inform your doctor if you have heart disease, high blood pressure, or thyroid disorders. |
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