MEDIHALER-ISO
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MEDIHALER-ISO (MEDIHALER-ISO).
Isoproterenol acts as a non-selective beta-adrenergic agonist, stimulating both beta-1 and beta-2 receptors, leading to increased heart rate, contractility, and bronchodilation.
| Metabolism | Primarily metabolized by catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO); also undergoes sulfation in the liver. |
| Excretion | Renal: 60% unchanged; biliary/fecal: 30% as conjugated metabolites |
| Half-life | Terminal half-life: 2 hours (range 1.5–3 hours) after inhalation; prolonged in hepatic impairment |
| Protein binding | 25–30% bound to albumin |
| Volume of Distribution | Vd: 1.5–2.5 L/kg; indicates extensive tissue distribution |
| Bioavailability | Inhalation: 10–20% (due to first-pass and local deposition); sublingual: 5–10%; oral: <5% |
| Onset of Action | Inhalation: 1–2 minutes; sublingual: 3–5 minutes; intravenous: immediate |
| Duration of Action | Inhalation: 30 minutes to 2 hours (dose-dependent); sublingual: 20–30 minutes; intravenous: 10–15 minutes |
1-2 inhalations (80-160 mcg) sublingually or by inhalation as needed for angina; maximum 6 inhalations per day.
| Dosage form | AEROSOL, METERED |
| Renal impairment | No dose adjustment required for GFR ≥30 mL/min; for GFR <30 mL/min, reduce dose by 50% or extend interval to every 6-8 hours. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: reduce dose by 75% or use with caution. |
| Pediatric use | Not recommended for use in children under 12 years; for children aged 12-18: 1 inhalation (80 mcg) sublingually as needed, maximum 2 inhalations per day. |
| Geriatric use | Initiate at lower end of dosing range (80 mcg as needed); monitor for hypotension and dizziness; adjust based on response and tolerability. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MEDIHALER-ISO (MEDIHALER-ISO).
| Breastfeeding | Excreted in breast milk in small amounts; M/P ratio approximately 0.9. Use with caution in nursing mothers, monitor infant for signs of beta-adrenergic stimulation (tachycardia, irritability). |
| Teratogenic Risk | FDA Pregnancy Category C. First trimester: Animal studies show teratogenicity at high doses; human data limited, avoid unless benefit outweighs risk. Second and third trimesters: Use cautiously due to potential fetal tachycardia and hypoglycemia; may inhibit uterine contractions. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to isoproterenol; cardiac arrhythmias associated with tachycardia; digitalis intoxication; ventricular fibrillation.
| Precautions | May cause arrhythmias, angina, or myocardial ischemia; excessive use can lead to paradoxical bronchospasm; caution in patients with hyperthyroidism, diabetes, or cardiovascular disease. |
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| Monitor maternal heart rate, blood pressure, and serum potassium. Fetal heart rate monitoring during prolonged use. Assess for signs of preterm labor inhibition or fetal distress. |
| Fertility Effects | No known adverse effects on fertility based on limited human data. Animal studies show no impairment of fertility at therapeutic doses. |