METAPROTERENOL SULFATE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for METAPROTERENOL SULFATE (METAPROTERENOL SULFATE).
Selective beta-2 adrenergic receptor agonist that activates adenylate cyclase, increasing intracellular cyclic AMP leading to bronchodilation and inhibition of mast cell mediator release.
| Metabolism | Primarily hepatic via sulfation and glucuronidation; minor CYP450 metabolism. |
| Excretion | Renal: 40-60% as unchanged drug and metabolites; biliary/fecal: ~40% as metabolites. |
| Half-life | Terminal elimination half-life: 2-6 hours. Clinical context: Shorter half-life requires frequent dosing; prolongation in renal impairment. |
| Protein binding | 10-20% bound to albumin. |
| Volume of Distribution | 0.5-1.0 L/kg, indicating distribution into total body water and some tissue binding. |
| Bioavailability | Oral: ~40% with extensive first-pass metabolism; Inhalation: 10-20% (dependent on technique and device); Intravenous: 100%. |
| Onset of Action | Oral: 15-30 minutes; Inhalation (metered-dose): 2-5 minutes; Subcutaneous: 5-15 minutes; Intravenous: Immediate. |
| Duration of Action | Oral: 2-4 hours; Inhalation: 2-6 hours; Subcutaneous: 1-2 hours; Intravenous: 30-90 minutes. Clinical note: Tolerance may develop with prolonged use. |
2.5 mg (0.25 mL of 1% solution) by nebulization every 6-8 hours. For oral, 20 mg every 6-8 hours.
| Dosage form | SOLUTION |
| Renal impairment | No specific guidelines for GFR-based dosing. Use with caution in severe renal impairment. |
| Liver impairment | No specific guidelines for Child-Pugh based dosing. |
| Pediatric use | Nebulized: 0.01 mL/kg of 1% solution (0.01 mL/kg = 0.1 mg/kg) every 6-8 hours, up to 0.3 mL. Oral: 0.3-0.5 mg/kg/dose every 6-8 hours. |
| Geriatric use | Start at lower end of dosing range due to increased sensitivity and possible concurrent diseases. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for METAPROTERENOL SULFATE (METAPROTERENOL SULFATE).
| Breastfeeding | Excreted in breast milk in unknown amounts. Potential for infant tachycardia and hypoglycemia. Use with caution, especially in preterm infants. M/P ratio not established. |
| Teratogenic Risk | Inadequate human data; animal studies not conducted. Beta-2 agonists may cause maternal tachycardia, hypoglycemia, and potential for fetal tachycardia. Avoid in first trimester due to theoretical risk of congenital anomalies; use in second/third trimester only if benefit outweighs potential fetal tachycardia or hypoglycemia. |
■ FDA Black Box Warning
None
| Common Effects | Orthostatic hypotension sudden lowering of blood pressure on standing Slow heart rate Headache Dizziness Tiredness Stomach pain Nausea Breathlessness |
| Serious Effects |
["Hypersensitivity to metaproterenol or any component","Cardiac tachyarrhythmias"]
| Precautions | ["Paradoxical bronchospasm may occur with excessive use","Cardiovascular effects including tachycardia, palpitations, and hypertension","Hypokalemia may occur","Diabetes mellitus: hyperglycemic effects","Tolerance to bronchodilator effects may develop"] |
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| Fetal Monitoring |
| Fetal heart rate monitoring during infusion; maternal heart rate, blood pressure, serum glucose, and potassium due to risk of hypokalemia and hyperglycemia. |
| Fertility Effects | No known effect on human fertility; animal studies not available. |