ISOETHARINE MESYLATE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ISOETHARINE MESYLATE (ISOETHARINE MESYLATE).
Selective beta-2 adrenergic receptor agonist; stimulates adenylate cyclase, increasing cAMP in bronchial smooth muscle, leading to bronchodilation.
| Metabolism | Primarily hepatic via catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO); also undergoes sulfate conjugation. |
| Excretion | Primarily renal excretion of unchanged drug and metabolites (sulfate and glucuronide conjugates); approximately 40-50% excreted renally as unchanged drug within 24 hours, with the remainder as metabolites. Biliary/fecal excretion is minimal (<5%). |
| Half-life | Terminal elimination half-life is approximately 2.5–5 hours in adults after inhalation; may be prolonged in patients with hepatic or renal impairment. |
| Protein binding | Approximately 15–30% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Approximately 0.5–1.0 L/kg, indicating distribution into total body water. |
| Bioavailability | Inhalation: 10–40% (dependent on nebulization efficiency and lung deposition); oral: negligible due to extensive first-pass metabolism (<5%). |
| Onset of Action | Inhalation: 1–5 minutes; intravenous: immediate; intramuscular/subcutaneous: 5–15 minutes. |
| Duration of Action | Inhalation: 1–3 hours (bronchodilation); longer duration (up to 4 hours) at higher doses. Tolerance may develop with prolonged use. |
Inhalation: 1-2 inhalations (0.34 mg per actuation) via metered-dose inhaler every 4-6 hours as needed; or 0.25-0.5 mL of 1% solution diluted in 2-3 mL of normal saline via nebulizer every 4-6 hours.
| Dosage form | AEROSOL, METERED |
| Renal impairment | No specific dosage adjustment required; use with caution in severe renal impairment due to potential accumulation of metabolites. |
| Liver impairment | No specific dosage adjustment guidelines; use with caution in severe hepatic impairment. |
| Pediatric use | Children: Inhalation via nebulizer: 0.01 mL/kg of 1% solution (maximum 0.5 mL) diluted in 2-3 mL normal saline every 4-6 hours; or 1-2 inhalations from metered-dose inhaler every 4-6 hours. |
| Geriatric use | Elderly patients may be more sensitive to adrenergic effects; initiate at lower doses and titrate cautiously; monitor for tachycardia, hypertension, and tremors. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ISOETHARINE MESYLATE (ISOETHARINE MESYLATE).
| Breastfeeding | Excretion in human milk unknown. Caution advised due to potential for beta-adrenergic stimulation in neonate. M/P ratio not established. |
| Teratogenic Risk | ISOETHARINE MESYLATE: Pregnancy Category C. No adequate studies in pregnant women. In animal studies, no teratogenic effects at doses up to 10 times the human dose. Risks to fetus include potential for maternal tachycardia and hypotension leading to reduced uteroplacental blood flow. Use only if clearly needed. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to isoetharine or any component; preexisting cardiac arrhythmias (especially tachyarrhythmias) associated with tachycardia.
| Precautions | May cause paradoxical bronchospasm, cardiovascular effects (tachycardia, hypertension, arrhythmias), hypokalemia, hyperglycemia; use with caution in patients with cardiovascular disorders, diabetes, hyperthyroidism, seizure disorders; tolerance may develop. |
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| Monitor maternal heart rate, blood pressure, and fetal heart rate during infusion. Assess for signs of maternal tachycardia or arrhythmia. In obstetrics, use tocolysis requires monitoring for pulmonary edema. |
| Fertility Effects | No known adverse effects on fertility in animal studies. Beta-agonists may theoretically affect fertility due to effects on uterine contractility, but no human data available. |