From the FDA Drug Label
For intramuscular administration, use a needle long enough (at least 1/2 inch to 5/8 inch) to ensure the injection is administered into the muscle. The best needle size for intramuscular epinephrine injections is a needle that is at least 1/2 inch to 5/8 inch long to ensure the injection is administered into the muscle 1.
- The key consideration is the length of the needle, rather than the gauge (thickness).
- The minimum length of 1/2 inch to 5/8 inch is recommended to ensure intramuscular administration.
From the Research
For intramuscular epinephrine injections, a 22-25 gauge needle with a length of 1-1.5 inches is generally recommended. This recommendation is based on the most recent and highest quality study available, which emphasizes the importance of needle length in ensuring effective medication delivery and patient comfort 2. The length of the needle is crucial to ensure that the medication reaches the muscle tissue rather than being deposited in subcutaneous fat, which would result in slower absorption and reduced effectiveness.
Key Considerations
- The preferred injection site for epinephrine is the mid-outer thigh (vastus lateralis muscle) as it provides reliable absorption and is easily accessible in emergency situations.
- When administering epinephrine for anaphylaxis, the standard dose is 0.3-0.5 mg (0.3-0.5 mL of 1:1000 concentration) for adults and 0.15 mg (0.15 mL) for children, with the needle inserted at a 90-degree angle to ensure intramuscular delivery.
- The relatively thin gauge (22-25) allows for quick injection while minimizing pain, which is particularly important in emergency situations where epinephrine administration is often required.
Supporting Evidence
- A study published in 2018 found that the risk of periosteal or intraosseous penetration was 32% in children weighing less than 15 kg when using high-pressure epinephrine auto-injectors (HPEAIs) with a needle length of 1 inch 2.
- Another study published in 2018 found that a 1-inch needle length was appropriate for 61% of infants, 88% of preschool children, 99% of school-aged children, and 95% of adolescents 3.
- A study published in 2009 found that the needle length on epinephrine auto-injectors was not long enough to reach the muscle in a significant number of children, highlighting the need for longer needles in certain populations 4.
Clinical Implications
- Healthcare providers should consider the patient's body habitus and weight when selecting an epinephrine auto-injector to ensure that the needle length is adequate for intramuscular delivery.
- Patients and caregivers should be educated on the proper use of epinephrine auto-injectors, including the importance of inserting the needle at a 90-degree angle and using the correct technique to ensure intramuscular delivery.