From the Guidelines
Racemic epinephrine and nebulized epinephrine are essentially the same medication delivered via nebulization, but they differ in their chemical composition, with racemic epinephrine containing a 50:50 mixture of both L-isomer and D-isomer forms of epinephrine, while nebulized epinephrine typically refers to L-epinephrine that has been diluted for nebulization. The key difference between the two lies in their chemical composition, but both are used to treat upper airway obstruction, particularly in conditions like croup, by causing vasoconstriction that reduces mucosal edema and improves airflow 1.
Key Differences and Uses
- Racemic epinephrine contains both L-isomer and D-isomer forms of epinephrine.
- Nebulized epinephrine typically refers to L-epinephrine diluted for nebulization.
- Both are used for upper airway obstruction, especially in croup.
- The typical dose for racemic epinephrine is 0.5 mL of 2.25% solution diluted in 3 mL of normal saline, while L-epinephrine is often given as 5 mL of 1:1000 (1 mg/mL) solution 1.
Clinical Effects and Monitoring
- Both medications have similar clinical effects and onset of action (about 10-30 minutes), with benefits lasting approximately 2 hours.
- Patients should be monitored for at least 2-3 hours after administration for potential rebound symptoms and side effects like tachycardia, hypertension, and tremors.
- Either formulation is acceptable in clinical practice, with the choice often depending on institutional availability rather than significant therapeutic differences.
Recommendation
Given the similarity in clinical effects and the primary difference being in chemical composition, the choice between racemic epinephrine and nebulized epinephrine should be based on institutional availability and patient-specific factors, with both being effective for the treatment of upper airway obstruction 1.
From the FDA Drug Label
Active ingredient (in each 0.5 ml) Racepinephrine, USP 11.25 mg (as 13.5 mg of Racepinephrine HCl, USP). The main difference between racemic Epinephrine and nebulized Epinephrine is the formulation and administration route.
- Racemic Epinephrine refers to a specific formulation of epinephrine that contains equal parts of the two enantiomers (mirror-image forms) of the molecule.
- Nebulized Epinephrine refers to the administration of epinephrine via a nebulizer, which is a device that converts the medication into a fine mist that can be inhaled. The FDA drug label does not provide information on the differences between these two forms of epinephrine beyond the formulation of racemic epinephrine 2.
From the Research
Difference between Racemic Epinephrine and Nebulized Epinephrine
- Racemic epinephrine is a mixture of two isomers, D- and L-epinephrine, whereas nebulized epinephrine can refer to either racemic epinephrine or L-epinephrine administered via a nebulizer 3, 4, 5, 6.
- Studies have shown that both racemic epinephrine and L-epinephrine are effective in treating croup, with no significant difference in efficacy between the two 4, 5, 6.
- Nebulized epinephrine, regardless of whether it is racemic or L-epinephrine, has been associated with a transient reduction in croup symptoms, with significant improvement in croup scores 30 minutes post-treatment 4, 5.
- The use of intermittent positive pressure breathing (IPPB) versus simple nebulization has not been shown to have a significant difference in efficacy 4, 5.
Comparison of Racemic and L-Epinephrine
- A study comparing racemic and L-epinephrine aerosols in the treatment of laryngotracheitis (croup) found that L-epinephrine was at least as effective as racemic epinephrine, with no additional adverse effects 6.
- Another study found that after two hours, L-epinephrine showed a significant reduction in croup score compared to racemic epinephrine 4, 5.