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. |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for VAPO-ISO (VAPO-ISO).
| Breastfeeding | Isoproterenol is excreted into breast milk in unknown amounts. The M/P ratio is not established. Due to its short half-life and poor oral bioavailability, infant exposure is likely low. However, monitor infant for signs of beta-adrenergic stimulation (tachycardia, irritability). Use with caution, especially in preterm infants. |
| 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. |
■ 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 component of the formulation; cardiac arrhythmias associated with tachycardia or digitalis toxicity; angina pectoris; myocardial infarction; and ventricular fibrillation.
| 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. |
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| 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. |