ISOETHARINE HYDROCHLORIDE S/F
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ISOETHARINE HYDROCHLORIDE S/F (ISOETHARINE HYDROCHLORIDE S/F).
Beta-2 adrenergic receptor agonist; relaxes bronchial smooth muscle by increasing cyclic AMP.
| Metabolism | Metabolized by catechol-O-methyltransferase (COMT) and sulfatase enzymes. |
| Excretion | Primarily renal excretion of unchanged drug and metabolites; 60-70% excreted in urine as unchanged drug and sulfate conjugates, with less than 10% eliminated in feces via biliary excretion. |
| Half-life | 2-4 hours; clinical context: short half-life supports continuous or repeated dosing for acute bronchospasm. |
| Protein binding | 20-30% bound primarily to albumin. |
| Volume of Distribution | Approximately 1.5-2.5 L/kg, indicating extensive distribution into tissues beyond plasma. |
| Bioavailability | Inhalation: 10-30% (systemic absorption); oral: very low due to first-pass metabolism (not clinically used). |
| Onset of Action | Inhalation: 1-3 minutes; subcutaneous: 5-10 minutes. |
| Duration of Action | Inhalation: 1-3 hours; subcutaneous: 1-2 hours; clinically, shorter duration than isoproterenol. |
Inhalation: 1-2 inhalations of a 340 mcg/metered dose every 4 hours as needed. Nebulization: 500 mcg (0.5 mL of a 0.1% solution) every 4 hours as needed.
| Dosage form | SOLUTION |
| Renal impairment | No specific adjustment recommended; use caution in severe impairment due to potential accumulation of metabolites. |
| Liver impairment | No specific adjustment recommended; use caution in severe hepatic impairment due to reduced clearance. |
| Pediatric use | Children <6 years: 0.01-0.02 mL/kg of 0.1% solution by nebulization; maximum 0.5 mL per dose. Children 6-12 years: 0.5 mL of 0.1% solution by nebulization every 4 hours. |
| Geriatric use | Elderly patients may have increased sensitivity; start at lower end of dosing range and titrate carefully due to potential cardiovascular effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ISOETHARINE HYDROCHLORIDE S/F (ISOETHARINE HYDROCHLORIDE S/F).
| Breastfeeding | Excreted in breast milk in small amounts. M/P ratio not determined. Beta-agonists may cause adverse effects in nursing infants (tachycardia, tremor). Use with caution, weighing benefit to mother against potential risk to infant. |
| Teratogenic Risk | FDA Pregnancy Category C. No adequate studies in pregnant women. In animal studies, beta-agonists have shown teratogenic effects (cleft palate, limb defects) at high doses. Risk to fetus cannot be ruled out; use only if potential benefit justifies risk. First trimester: limited data, theoretical risk of teratogenicity. Second/third trimesters: may cause fetal tachycardia, hypoglycemia, and hypocalcemia due to beta-adrenergic stimulation. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to isoetharine or any component","Pre-existing cardiac arrhythmias associated with tachycardia"]
| Precautions | ["Paradoxical bronchospasm","Cardiovascular effects (tachycardia, hypertension)","Hypokalemia","Immediate hypersensitivity reactions"] |
| Food/Dietary | No known food interactions; avoid caffeine intake as it may increase cardiovascular side effects. |
| Clinical Pearls | Isoetharine is a selective beta-2 agonist used primarily for acute bronchospasm in asthma or COPD. It is administered via nebulization; an adequate tidal volume is essential for drug delivery. Tachyphylaxis can occur with excessive use; monitor for paradoxical bronchospasm. Cardiotoxicity (tachycardia, arrhythmia) is possible, especially in hypoxemic patients. |
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| Fetal Monitoring | Monitor maternal heart rate, blood pressure, ECG, serum potassium and glucose levels. In pregnancy: fetal heart rate monitoring (risk of tachycardia), assess for signs of preterm labor suppression. Regular ultrasound to monitor fetal growth and amniotic fluid volume. |
| Fertility Effects | No specific studies on fertility in humans. In animal studies, high doses of beta-agonists may impair fertility (delayed implantation, reduced litter size). Clinical relevance uncertain. |
| Patient Advice | Use only as directed; do not increase dose or frequency without consulting your doctor. · If the solution turns pink, it may be exposed to air or oxidizing agents; discard if discolored or cloudy. · Rinse your mouth with water after use to prevent throat irritation. · Seek immediate medical help if you experience chest pain, rapid heartbeat, or worsening breathing. · Inform your doctor if you are pregnant, breastfeeding, or have heart disease, high blood pressure, or seizures. |