What is the difference between norepinephrine (norepi) and epinephrine (epi)?

From the Guidelines

Norepinephrine and epinephrine are both catecholamine medications used in critical care settings, but they differ in their receptor activity and clinical effects, with norepinephrine being the preferred first-line vasopressor for septic shock and epinephrine being preferred for anaphylaxis and cardiac arrest. The main difference between norepinephrine (norepi) and epinephrine (epi) lies in their receptor activity and clinical effects.

• Norepinephrine primarily affects alpha-1 adrenergic receptors with moderate beta-1 activity, making it a potent vasoconstrictor that increases blood pressure with less effect on heart rate.
• Epinephrine has stronger beta-1 and beta-2 effects in addition to alpha-1 activity, causing more pronounced increases in heart rate, contractility, and potential vasodilation at lower doses. Some key points to consider when using these medications include:
• Norepinephrine is typically used as a first-line vasopressor for septic shock, starting at 0.01-0.03 mcg/kg/min and titrating up to 0.5 mcg/kg/min as needed 1.
• Epinephrine is preferred for anaphylaxis, cardiac arrest (1 mg IV every 3-5 minutes), and as a second-line agent for shock at 0.01-0.5 mcg/kg/min 2, 3.
• The key physiological difference is that epinephrine's greater beta stimulation increases cardiac output and heart rate more significantly, while potentially causing more arrhythmias, increased myocardial oxygen demand, and lactate production compared to norepinephrine 4. When administering either medication, central venous access is preferred, and continuous blood pressure monitoring is essential 1, 5. It's also important to note that the use of these medications should be guided by the patient's individual needs and clinical response, and that the dosages and administration routes may vary depending on the specific clinical scenario. Overall, the choice between norepinephrine and epinephrine depends on the specific clinical context and the patient's individual needs, and should be guided by the latest clinical evidence and guidelines 6, 7, 1, 5.

From the FDA Drug Label

Norepinephrine (sometimes referred to as l-arterenol/Levarterenol or l-norepinephrine) is a sympathomimetic amine which differs from epinephrine by the absence of a methyl group on the nitrogen atom Epinephrine is a sympathomimetic catecholamine (adrenergic agent) designated chemically as 4-[1-hydroxy-2 (methylamino) ethyl]-1,2 benzenediol, a white, crystalline powder.

The main difference between norepinephrine (norepi) and epinephrine (epi) is the presence of a methyl group on the nitrogen atom in epinephrine, which is absent in norepinephrine 8, 9.

• Chemical structure: Norepinephrine has the structural formula of (-)-α-(aminomethyl)-3,4-dihydroxybenzyl alcohol tartrate (1:1) (salt) monohydrate, while epinephrine has the structural formula of 4-[1-hydroxy-2 (methylamino) ethyl]-1,2 benzenediol.
• Pharmacological classification: Both are sympathomimetic amines, but they have different effects on the body due to their distinct chemical structures.

From the Research

Difference between Norepinephrine (Norepi) and Epinephrine (Epi)

• Norepinephrine and epinephrine are both vasopressors used in the treatment of septic shock, but they have different effects on the body 10, 11.
• Norepinephrine is currently the first-line vasopressor for septic shock, as it has been shown to decrease all-cause mortality and have a better hemodynamic profile compared to dopamine 10.
• Epinephrine, on the other hand, is considered a second-line agent, and its use is often reserved for patients who are refractory to norepinephrine 10, 11.
• Studies have compared the outcomes of patients treated with norepinephrine and epinephrine, and have found that there are no significant differences in mortality rates or hemodynamic measurements between the two groups 11, 12.
• However, norepinephrine may have a lower risk of adverse events, such as cardiac arrhythmias, compared to epinephrine 10, 13.
• The optimal dosing and timing of norepinephrine and epinephrine in septic shock are still debated, and further research is needed to determine the best treatment strategies 14.

Clinical Use

• Norepinephrine is often started early in the treatment of septic shock to correct hypotension and improve organ perfusion 14.
• The optimal blood pressure target for norepinephrine is individualized, but a mean arterial pressure of at least 65 mmHg is often recommended 14.
• Epinephrine may be added to norepinephrine in patients who are refractory to treatment, but its use should be carefully considered due to the potential for adverse events 11, 14.

Summary of Findings

• Norepinephrine is the first-line vasopressor for septic shock, due to its ability to decrease mortality and improve hemodynamic measurements 10.
• Epinephrine is a second-line agent, and its use should be reserved for patients who are refractory to norepinephrine 10, 11.
• Further research is needed to determine the optimal dosing and timing of norepinephrine and epinephrine in septic shock 14.