Lidocaine Dilution for 1 gram Intramuscular Ceftriaxone (Rocephin)
Mix 1 gram of ceftriaxone powder with 3.6 mL of 1% lidocaine solution (without epinephrine) to achieve a final concentration of approximately 250 mg/mL, or use 2.1 mL of 1% lidocaine for a more concentrated 350 mg/mL solution. 1
Standard Reconstitution Protocol
The FDA-approved ceftriaxone labeling provides specific volumes for lidocaine dilution 1:
- For 250 mg/mL concentration: Add 3.6 mL of 1% lidocaine solution to the 1 gram vial 1
- For 350 mg/mL concentration: Add 2.1 mL of 1% lidocaine solution to the 1 gram vial 1
After adding the diluent, shake the vial thoroughly to form the solution, then withdraw the entire contents into a syringe 1.
Critical Safety Considerations
Use only 1% lidocaine solution WITHOUT epinephrine as the diluent for intramuscular ceftriaxone 1. The reconstituted solution remains stable for 24 hours at room temperature (25°C) or 3 days when refrigerated at 4°C 1.
Injection Technique
- Inject the medication deep into the body of a relatively large muscle 1
- Aspirate before injection to avoid unintentional intravascular administration 1
- The lidocaine diluent significantly reduces injection pain compared to sterile water 2, 3
Evidence Supporting Lidocaine as Diluent
Research demonstrates that lidocaine as a diluent for ceftriaxone provides substantial pain reduction without altering the drug's pharmacokinetics 3. A randomized study showed that 1% lidocaine does not affect the elimination parameters or bioavailability of intramuscularly administered ceftriaxone, while considerably reducing both the intensity and frequency of injection site pain 3. Another prospective study confirmed that adolescents receiving ceftriaxone with lidocaine diluent experienced significantly less pain at multiple time intervals (immediately post-injection, 10 minutes, 20 minutes, and 6 hours) compared to sterile water 2.
Common Pitfalls to Avoid
- Never use calcium-containing diluents (such as Ringer's solution or Hartmann's solution) as they cause precipitation with ceftriaxone 1
- Do not use lidocaine solutions containing epinephrine for this purpose 1
- Avoid using bacteriostatic water with benzyl alcohol if the more concentrated solution is needed, as stability is reduced to 24 hours at room temperature 1
- Do not exceed the recommended diluent volumes, as this will alter the final concentration and potentially affect dosing accuracy 1