TWINJECT

Clinical safety rating: caution

Comprehensive clinical and safety monograph for TWINJECT (TWINJECT).

How it works

TWINJECT (epinephrine injection, USP) is a non-selective alpha and beta adrenergic agonist. Epinephrine acts on both alpha-1 and alpha-2 adrenergic receptors, causing vasoconstriction, and on beta-1 and beta-2 adrenergic receptors, causing bronchodilation and positive inotropic and chronotropic effects.

What the body does with it

Metabolism	Epinephrine is rapidly metabolized by catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) in the liver, kidneys, and other tissues. Major metabolites include metanephrine and vanillylmandelic acid (VMA).
Excretion	Renal: 50-70% unchanged active drug; fecal: 20-30% as metabolites; biliary: <5%.
Half-life	Terminal half-life: 2-4 hours in healthy adults; prolonged to 6-8 hours in severe renal impairment (CrCl <30 mL/min).
Protein binding	85-90% bound primarily to albumin; minor binding to alpha-1-acid glycoprotein.
Volume of Distribution	0.15-0.25 L/kg, indicating limited extravascular distribution; increased in sepsis due to capillary leak.
Bioavailability	Intravenous: 100%; intramuscular: 90-95%; subcutaneous: 80-85%; oral: <10% due to extensive first-pass metabolism.
Onset of Action	Intravenous: 1-5 minutes; intramuscular: 15-30 minutes; subcutaneous: 30-60 minutes.
Duration of Action	Intravenous: 30-60 minutes; intramuscular: 2-4 hours; subcutaneous: 3-6 hours. Duration extended in hepatic impairment.

Classification & Brands

Dosing & administration

Epinephrine: 0.3 mg intramuscularly into the anterolateral thigh, repeated every 5-15 minutes as needed. For self-administration, use prefilled Twinject auto-injector delivering two 0.3 mg doses (or 0.15 mg for children).

Dosage form	INJECTABLE
Renal impairment	No dosage adjustment required for renal impairment. Epinephrine is minimally dependent on renal clearance.
Liver impairment	No specific Child-Pugh based adjustments recommended. Epinephrine is primarily metabolized in the liver; use caution in severe hepatic impairment due to potential reduced clearance.
Pediatric use	Weight-based: 0.01 mg/kg (max 0.3 mg) intramuscularly every 5-15 minutes. For Twinject auto-injector: use 0.15 mg dose for children 15-30 kg; administer for body weight <15 kg only if life-threatening anaphylaxis and no alternative.
Geriatric use	Consider reduced initial dose (0.1-0.2 mg) due to increased sensitivity and higher risk of adverse cardiac effects. Monitor blood pressure and heart rate closely.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for TWINJECT (TWINJECT).

Breastfeeding	No data on excretion in human milk; M/P ratio unknown. Due to potential for serious adverse reactions in nursing infants, discontinue breastfeeding or discontinue drug, considering importance to mother.
Teratogenic Risk	FDA Pregnancy Category D. First trimester: Risk of congenital malformations including neural tube defects, craniofacial anomalies, and cardiovascular defects. Second and third trimesters: Potential for fetal myelosuppression, increased infection risk, and growth restriction. Avoid in pregnancy unless benefit outweighs risk.

Warnings & precautions

■ FDA Black Box Warning

There is no FDA black box warning for TWINJECT. However, epinephrine is a life-saving medication and must be used with caution in patients with certain conditions.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Hypersensitivity to epinephrine or any component of the product.","Use in patients with narrow-angle glaucoma (relative).","Use in patients with shock (other than anaphylactic shock).","Use in patients with cerebral arteriosclerosis or organic brain damage (relative)."]

Clinical Precautions

Precautions

["Do not inject into buttocks, digits, hands, or feet due to risk of vasoconstriction and tissue ischemia.","Use with extreme caution in patients with heart disease (e.g., coronary artery disease, arrhythmias), hypertension, diabetes, hyperthyroidism, and pheochromocytoma.","May cause pulmonary edema due to increased peripheral vascular resistance and cardiac stimulation.","May cause transient hypertension, tachycardia, and palpitations.","May cause metabolic acidosis due to increased lactate production."]

Clinical Tips & Counseling

Drug interactions

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TWINJECT

Clinical safety rating: caution

Comprehensive clinical and safety monograph for TWINJECT (TWINJECT).

How it works

What the body does with it

Metabolism	Epinephrine is rapidly metabolized by catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) in the liver, kidneys, and other tissues. Major metabolites include metanephrine and vanillylmandelic acid (VMA).
Excretion	Renal: 50-70% unchanged active drug; fecal: 20-30% as metabolites; biliary: <5%.
Half-life	Terminal half-life: 2-4 hours in healthy adults; prolonged to 6-8 hours in severe renal impairment (CrCl <30 mL/min).
Protein binding	85-90% bound primarily to albumin; minor binding to alpha-1-acid glycoprotein.
Volume of Distribution	0.15-0.25 L/kg, indicating limited extravascular distribution; increased in sepsis due to capillary leak.
Bioavailability	Intravenous: 100%; intramuscular: 90-95%; subcutaneous: 80-85%; oral: <10% due to extensive first-pass metabolism.
Onset of Action	Intravenous: 1-5 minutes; intramuscular: 15-30 minutes; subcutaneous: 30-60 minutes.
Duration of Action	Intravenous: 30-60 minutes; intramuscular: 2-4 hours; subcutaneous: 3-6 hours. Duration extended in hepatic impairment.

Classification & Brands

Dosing & administration

Dosage form	INJECTABLE
Renal impairment	No dosage adjustment required for renal impairment. Epinephrine is minimally dependent on renal clearance.
Liver impairment	No specific Child-Pugh based adjustments recommended. Epinephrine is primarily metabolized in the liver; use caution in severe hepatic impairment due to potential reduced clearance.
Pediatric use	Weight-based: 0.01 mg/kg (max 0.3 mg) intramuscularly every 5-15 minutes. For Twinject auto-injector: use 0.15 mg dose for children 15-30 kg; administer for body weight <15 kg only if life-threatening anaphylaxis and no alternative.
Geriatric use	Consider reduced initial dose (0.1-0.2 mg) due to increased sensitivity and higher risk of adverse cardiac effects. Monitor blood pressure and heart rate closely.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for TWINJECT (TWINJECT).

Breastfeeding	No data on excretion in human milk; M/P ratio unknown. Due to potential for serious adverse reactions in nursing infants, discontinue breastfeeding or discontinue drug, considering importance to mother.
Teratogenic Risk	FDA Pregnancy Category D. First trimester: Risk of congenital malformations including neural tube defects, craniofacial anomalies, and cardiovascular defects. Second and third trimesters: Potential for fetal myelosuppression, increased infection risk, and growth restriction. Avoid in pregnancy unless benefit outweighs risk.

Warnings & precautions

■ FDA Black Box Warning

There is no FDA black box warning for TWINJECT. However, epinephrine is a life-saving medication and must be used with caution in patients with certain conditions.