MEDIHALER-ISO
Clinical safety rating
cautionComprehensive 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 |
| Molecular Weight | 316.43 |
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 | Avoid during first trimester due to risk of fetal hypoxia from maternal hypotension and potential teratogenicity based on animal studies; case reports of congenital anomalies with isoproterenol use. |
| 2nd trimester | Use only if clearly needed; may cause fetal tachycardia and hypoglycemia; risk of preterm labor due to beta-adrenergic effects. |
| 3rd trimester | Use with caution; may inhibit uterine contractions and cause fetal tachycardia; risk of maternal cardiac arrhythmias. |
Clinical note
Comprehensive clinical and safety monograph for MEDIHALER-ISO (MEDIHALER-ISO).
| Placental transfer | Crosses placenta; rapidly transferred to fetus with fetal concentrations approximately 50% of maternal levels. |
| Breastfeeding | Isoproterenol is excreted into breast milk in small amounts; however, due to its short half-life and poor oral bioavailability, significant infant exposure is unlikely. Monitor infant for signs of beta-adrenergic stimulation (tachycardia, irritability). |
| Lactation Rating | L2: Safer |
| 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 | 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. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to isoproterenol or any componentTachyarrhythmias (e.g., ventricular tachycardia) not associated with bradycardiaDigitalis toxicity-induced arrhythmiasCoronary insufficiency or myocardial infarction during acute phaseSevere hypoxia or hypercapnia (may precipitate arrhythmias)
| Precautions | May cause arrhythmias, angina, or myocardial ischemia; excessive use can lead to paradoxical bronchospasm; caution in patients with hyperthyroidism, diabetes, or cardiovascular disease. |
| Food/Dietary | No specific food interactions. Avoid excessive caffeine as it may increase cardiac stimulation. |
| Clinical Pearls | MEDIHALER-ISO (isoproterenol) is a non-selective beta-adrenergic agonist used for bronchospasm. Monitor for tachycardia, palpitations, and cardiac arrhythmias. Use with caution in patients with coronary artery disease, hyperthyroidism, or diabetes. Tolerance can develop with prolonged use. Avoid concomitant use with other sympathomimetics or beta-blockers. |
| Patient Advice | Use exactly as prescribed; do not exceed recommended dose. · Rinse mouth after inhalation to reduce side effects. · Seek medical attention if symptoms worsen or you need more inhalations than usual. · Report chest pain, rapid heart rate, or tremors. · Store at room temperature away from heat and open flame (aerosol). |
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