VAPO-ISO
Clinical safety rating: caution
Comprehensive clinical and safety monograph for VAPO-ISO (VAPO-ISO).
VAPO-ISO (isoproterenol) is a non-selective beta-adrenergic agonist that stimulates both beta-1 and beta-2 adrenergic receptors. It increases heart rate, contractility, and conduction velocity (beta-1), and causes bronchodilation and peripheral vasodilation (beta-2).
| Metabolism | Primarily metabolized by catechol-O-methyltransferase (COMT) in the liver and other tissues. Also undergoes sulfation and glucuronidation. |
| Excretion | Renal excretion of unchanged drug (30–50%) and hepatic metabolism to inactive metabolites. Fecal excretion is negligible (<2%). |
| Half-life | Terminal elimination half-life is 2–4 hours (mean 3 hours). In severe renal impairment (CrCl <30 mL/min), half-life may be prolonged to 8–12 hours, requiring dose adjustment. |
| Protein binding | ~40% (primarily to albumin). |
| Volume of Distribution | 0.5–0.7 L/kg. This relatively small Vd indicates limited extravascular distribution, consistent with a hydrophilic molecule primarily in extracellular fluid. |
| Bioavailability | Inhalation: 15–25% (due to local deposition and partial absorption). Intravenous: 100%. |
| Onset of Action | Inhalation: 1–3 minutes (peak bronchodilation). Intravenous: <1 minute. |
| Duration of Action | Inhalation: 3–6 hours (bronchodilation). Intravenous: 1–2 hours (based on clinical effect on heart rate and blood pressure). Tolerance may develop with continuous use. |
| Molecular Weight | 211.26 |
Inhalation: 1-2 inhalations of a 0.5% solution for acute bronchospasm; 0.5 mL of 1:200 solution via nebulizer every 4-6 hours as needed.
| Dosage form | SOLUTION |
| Renal impairment | No specific adjustment required; drug primarily hepatically metabolized. |
| Liver impairment | No specific guidelines; caution in severe hepatic impairment due to potential for increased systemic exposure. |
| Pediatric use | Inhalation: 0.01-0.03 mL/kg of 1:200 solution via nebulizer, up to 0.5 mL, every 4-6 hours as needed. |
| Geriatric use | Initiate at lower end of dosing range; monitor for cardiovascular effects such as tachycardia and hypertension. |
| 1st trimester | Isoproterenol is generally avoided in pregnancy, especially in the first trimester, due to potential fetal tachycardia and possible teratogenic effects; use only if clearly needed and benefit outweighs risk. |
| 2nd trimester | May be used cautiously for severe bradycardia or heart block when alternative therapies fail; monitor maternal and fetal heart rate. |
| 3rd trimester | May be used with caution near term; can cause maternal and fetal tachycardia, and may inhibit uterine contractions; use only if clearly indicated. |
Clinical note
Comprehensive clinical and safety monograph for VAPO-ISO (VAPO-ISO).
| Placental transfer | Isoproterenol crosses the placenta; the degree is dependent on lipid solubility and molecular size; fetal serum levels may approach maternal levels. |
| Breastfeeding | Isoproterenol is rapidly metabolized and excreted in breast milk in small amounts; risk to infant is low. However, due to potential for cardiovascular effects, caution is advised; monitor infant for tachycardia or irritability. |
■ FDA Black Box Warning
VAPO-ISO may cause arrhythmias, myocardial ischemia, and cardiac arrest, especially in patients with pre-existing heart disease or those receiving other cardiotonic drugs. Use with caution in patients with myocardial infarction.
| Serious Effects |
Hypersensitivity to isoproterenol or any componentCardiac arrhythmias (e.g., ventricular tachycardia, atrial fibrillation with rapid ventricular response)Angina pectorisPre-existing myocardial ischemia or infarctionConcurrent use with epinephrine or other sympathomimetics (risk of serious arrhythmias)
| Precautions | Use with caution in patients with coronary insufficiency, diabetes, hyperthyroidism, or hypertension. May cause angina, palpitations, or cardiac arrhythmias. Tachyphylaxis may develop with prolonged use. |
| Food/Dietary | No specific food interactions. However, caffeine and stimulants may exacerbate cardiovascular effects. Avoid excessive consumption of caffeine-containing products like coffee, tea, and soda. |
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| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Isoproterenol is a beta-adrenergic agonist. In animal studies, beta-agonists have been associated with teratogenic effects at high doses. In humans, limited data do not indicate a major teratogenic risk. First trimester: Use only if clearly needed; no known structural anomalies. Second and third trimesters: May cause fetal tachycardia, hyperglycemia, and possibly inhibit uterine contractions. Avoid prolonged use near term due to risk of uterine relaxation and postpartum hemorrhage. |
| Fetal Monitoring | Monitor maternal heart rate, blood pressure, ECG for arrhythmias. Monitor fetal heart rate via continuous electronic fetal monitoring during intravenous administration. Assess maternal blood glucose, potassium levels. Observe for signs of uterine relaxation. |
| Fertility Effects | No human data on fertility effects. In animal studies, beta-agonists did not impair fertility at therapeutic doses. Isoproterenol may affect uterine contractility, but no direct evidence of negative impact on fertility. |
| Clinical Pearls | VAPO-ISO (isoproterenol inhalant) is used for bronchospasm during anesthesia. Administer via nebulization. Monitor for tachycardia, palpitations, and arrhythmias. Avoid in patients with pre-existing cardiac conditions such as coronary artery disease or tachyarrhythmias. Use with caution in hyperthyroidism and diabetes. Rapid onset but short duration; repeated dosing may be needed. Contraindicated in patients with ventricular fibrillation or digitalis toxicity. |
| Patient Advice | Use only as directed by your healthcare provider. · Do not exceed the prescribed dose or frequency. · Inform your doctor if you have heart disease, high blood pressure, thyroid problems, or diabetes. · Seek emergency help if you experience chest pain, rapid heart rate, or severe dizziness. · Keep the inhaler clean and follow storage instructions. |