NCLEX-PN® ExaminationPharmacological TherapiesMedium
An LPN is preparing to administer an intramuscular (IM) injection of a viscous medication to an adult client. Which needle gauge and length are most appropriate for this injection?
- A18-gauge, 2-inch
- B25-gauge, 5/8-inch
- C21-gauge, 1 1/2-inch
- D23-gauge, 1-inch
Show answer & explanationAnswer & explanation
Correct answer: C. 21-gauge, 1 1/2-inch
For viscous IM medications in an adult, a larger gauge (smaller number) needle is needed to allow the medication to flow, and a longer needle is required to ensure deep muscle penetration. A 21-gauge, 1 1/2-inch needle is a common and appropriate choice for this scenario. A 23-gauge, 1-inch might be too small in gauge and too short for a viscous IM for many adults.
Why the other options are wrong
- A. An 18-gauge is typically too large for routine IM injections and can cause unnecessary pain and tissue trauma; 2-inch length is usually for obese clients.
- B. A 25-gauge is too small for viscous medication, and 5/8-inch is too short for IM in an adult.
- D. A 23-gauge may be too small for viscous medication, and 1-inch might not be long enough to reach the muscle in all adults.
IM Injection Needle Selection
Choosing the correct needle gauge and length for intramuscular injections based on medication viscosity, client's body habitus, and injection site.
- Viscous meds need larger gauge (smaller number).
- Needle length depends on client size and site.
- Adult IM: 1-1.5 inch length common.
Memory trick: Gauge for Go, Length for Location, Viscosity for Velocity!