ISOPROTERENOL HYDROCHLORIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ISOPROTERENOL HYDROCHLORIDE (ISOPROTERENOL HYDROCHLORIDE).
Beta-adrenergic agonist with non-selective affinity for β1 and β2 receptors; increases myocardial contractility, heart rate, and bronchodilation via Gs-protein activation and cAMP elevation.
| Metabolism | Primarily hepatic via catechol-O-methyltransferase (COMT); also metabolized by monoamine oxidase (MAO) to a lesser extent. |
| Excretion | Primarily renal excretion of sulfate conjugates and unchanged drug; biliary/fecal excretion is minimal. |
| Half-life | Terminal elimination half-life is 2-3 minutes; clinically, catechol-O-methyltransferase (COMT)-mediated metabolism leads to rapid clearance. |
| Protein binding | Approximately 60% bound to plasma proteins (albumin and alpha1-acid glycoprotein). |
| Volume of Distribution | 0.5-1 L/kg; indicates extensive distribution into tissues, including heart, lungs, and skeletal muscle. |
| Bioavailability | Oral: negligible due to first-pass metabolism in the liver and gut wall; sublingual: approximately 10-20%; inhalation: high local bioavailability but systemic absorption is variable. |
| Onset of Action | IV: immediate (seconds); IM: 10-15 minutes; subcutaneous: 15-30 minutes; inhaled: 1-2 minutes. |
| Duration of Action | IV: 5-10 minutes; IM: 1-2 hours; subcutaneous: 1-2 hours; inhaled: 1-2 hours duration but requires frequent dosing due to short half-life. |
Initial IV infusion: 0.5-5 mcg/min, titrated to heart rate and blood pressure; typical range 2-10 mcg/min. IV bolus: 10-20 mcg as needed. Continuous infusion: 0.01-0.5 mcg/kg/min (max 30 mcg/min).
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment recommended; use with caution in severe renal impairment due to potential electrolyte disturbances. |
| Liver impairment | Child-Pugh Class A: no adjustment. Child-Pugh B/C: consider 50% dose reduction and titrate cautiously. |
| Pediatric use | IV infusion: 0.05-0.3 mcg/kg/min, titrated to effect. IV bolus: 0.1-1 mcg/kg. Maximum rate: 1 mcg/kg/min. |
| Geriatric use | Lower initial doses (0.5-1 mcg/min) and slower titration due to increased sensitivity and risk of tachyarrhythmias and myocardial ischemia. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ISOPROTERENOL HYDROCHLORIDE (ISOPROTERENOL HYDROCHLORIDE).
| Breastfeeding | It is unknown if isoproterenol is excreted in human breast milk. No M/P ratio is available. Because many drugs are excreted in milk, caution should be exercised when administered to nursing women. Beta-adrenergic agonists may suppress lactation. Limited data suggest minimal excretion, but risk to infant cannot be excluded. |
| Teratogenic Risk | Isoproterenol hydrochloride is a beta-adrenergic agonist. Animal studies have not been conducted; there are no adequate and well-controlled studies in pregnant women. It should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Due to its vasoactive properties, there is a theoretical risk of reduced uteroplacental blood flow, especially in the first and second trimesters, which could lead to fetal hypoxia. In the third trimester, use may cause uterine relaxation and potential delay in labor. |
■ FDA Black Box Warning
None
| Serious Effects |
["Tachyarrhythmias (e.g., ventricular fibrillation)","Angina pectoris","Known hypersensitivity to isoproterenol or sulfites (in some preparations)"]
| Precautions | ["May cause myocardial ischemia, arrhythmias, or hypotension","Use with caution in patients with ischemic heart disease, diabetes, hyperthyroidism, or prostatic hypertrophy","Tolerance may develop with prolonged use"] |
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| Fetal Monitoring | Monitor maternal heart rate, blood pressure, ECG, and signs of myocardial ischemia. Assess fetal heart rate continuously if used for tocolysis or during pregnancy. Monitor for signs of uterine hyperstimulation or fetal distress. Assess maternal serum potassium and glucose levels periodically due to metabolic effects of beta-agonists. |
| Fertility Effects | No human data on fertility effects. In animal studies, beta-adrenergic agonists have been associated with impaired fertility and reduced implantation rates at high doses. Clinically, short-term use is unlikely to affect fertility, but chronic use may interfere with ovulatory function due to altered adrenergic signaling. |