SYMJEPI
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SYMJEPI (SYMJEPI).
Symjepi (epinephrine) is a direct-acting sympathomimetic amine that acts on alpha- and beta-adrenergic receptors. Alpha-adrenergic receptor activation leads to vasoconstriction, increased peripheral vascular resistance, and decreased mucosal edema. Beta-adrenergic receptor activation results in bronchodilation, positive inotropic and chronotropic cardiac effects, and relaxation of gastrointestinal smooth muscle.
| Metabolism | Epinephrine is metabolized primarily by catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) in the liver and other tissues. Major metabolites include metanephrine and vanillylmandelic acid (VMA), which are excreted in the urine. |
| Excretion | Epinephrine is rapidly metabolized in the liver and other tissues by catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO). Metabolites, primarily metanephrine and vanillylmandelic acid (VMA), are excreted in urine. Less than 5% of administered dose is excreted unchanged in urine. Biliary/fecal elimination is negligible. |
| Half-life | The terminal elimination half-life of epinephrine is approximately 2-3 minutes when administered intravenously. This short half-life reflects rapid metabolic clearance and necessitates continuous infusion for sustained effect. After intramuscular injection, absorption is slower, but elimination half-life remains brief (about 2-5 minutes for the beta phase). The clinical context: Due to rapid clearance, the drug's effects wane quickly after discontinuation. |
| Protein binding | Epinephrine is approximately 50% bound to plasma proteins, primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | The volume of distribution (Vd) for epinephrine is 0.2-0.4 L/kg. This low Vd indicates that epinephrine is primarily confined to the extracellular fluid space and does not extensively distribute into tissues. |
| Bioavailability | Intramuscular (IM): Bioavailability is approximately 100% after IM injection into the vastus lateralis. Subcutaneous (SC): Bioavailability is variable, estimated at 50-80% due to local vasoconstriction reducing absorption. Oral: Essentially zero due to rapid metabolism in the gut wall and liver. Intratracheal: Bioavailability is about 10-20% for nebulized epinephrine. |
| Onset of Action | Intravenous (IV): Immediate (within seconds). Intramuscular (IM) injection into the anterolateral thigh: Within 5-10 minutes. Subcutaneous (SC): Within 5-15 minutes. Inhalation (nebulized): Within 1-5 minutes. |
| Duration of Action | IV: Short duration, about 5-10 minutes due to rapid metabolism. IM: Duration of bronchodilation and pressor effects about 20-30 minutes; effects on allergic reactions may persist longer due to absorption depot. SC: Similar to IM, 20-30 minutes. Clinical note: Duration is dose-dependent and may be prolonged with higher doses or in patients with hepatic impairment. |
0.3 mg intramuscular (IM) or subcutaneous (SC) injection into anterolateral aspect of thigh, repeat every 5-15 minutes as needed for anaphylaxis.
| Dosage form | SOLUTION |
| Renal impairment | No dose adjustment required; epinephrine is not renally eliminated. |
| Liver impairment | No dose adjustment required; epinephrine is metabolized in liver but severe hepatic impairment does not necessitate dose modification. |
| Pediatric use | Weight <30 kg: 0.15 mg IM/SC; weight ≥30 kg: 0.3 mg IM/SC; administer into anterolateral thigh; repeat every 5-15 minutes as needed. |
| Geriatric use | No specific dose adjustment; use standard adult dose with caution due to increased risk of adverse cardiovascular effects in elderly patients with cardiovascular disease. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for SYMJEPI (SYMJEPI).
| Breastfeeding | Epinephrine is excreted into breast milk in small amounts. M/P ratio approximately 1.0. Rapidly metabolized in infant gut. Use with caution; monitor infant for tachycardia or hypertension. Generally considered compatible with breastfeeding when clinically indicated. |
| Teratogenic Risk | FDA Pregnancy Category C. No adequate studies in pregnant women. In animal studies, epinephrine caused fetal hypoxia, reduced uterine blood flow, and skeletal anomalies at high doses. First trimester: risk of fetal hypoperfusion and potential teratogenicity. Second and third trimesters: may cause uterine vasoconstriction and fetal hypoxia. Avoid use during labor unless needed for anaphylaxis. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to epinephrine or any component of the formulation (except as emergency treatment for anaphylaxis)","Concurrent use of non-selective beta-blockers (relative contraindication due to risk of unopposed alpha-adrenergic effects)","Severe hypertension or ventricular fibrillation (except in cardiac resuscitation protocols)","In patients with angle-closure glaucoma (use with caution)"]
| Precautions | ["Cardiac effects: May cause tachycardia, arrhythmias, or myocardial ischemia, especially in patients with preexisting cardiac disease or those taking other drugs that sensitize the heart to arrhythmias.","Hypertension and stroke: Use with caution in patients with hypertension, hyperthyroidism, or cerebrovascular insufficiency.","Pulmonary edema: Reported with excessive doses.","Extravasation: Risk of tissue necrosis if injected into blood vessels; inject only into the anterolateral aspect of the thigh (mid-thigh) during anaphylaxis.","Use with caution in patients with diabetes: May increase blood glucose levels.","Pheochromocytoma: May precipitate hypertensive crisis.","Pregnancy: Use only if clearly needed (category C)."] |
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| Fetal Monitoring | Monitor maternal blood pressure, heart rate, ECG, and oxygen saturation. Assess for signs of anaphylaxis. In pregnancy, monitor fetal heart rate patterns and uterine activity if prolonged use. |
| Fertility Effects | No known adverse effects on fertility in animal studies. Clinical data insufficient to determine effects on human fertility. |