Mixing Rocephin (Ceftriaxone) with Lidocaine
Yes, Rocephin (ceftriaxone) can be safely mixed with 1% lidocaine solution as a diluent for intramuscular injections to reduce injection pain. 1
Evidence-Based Rationale
The FDA drug label for ceftriaxone explicitly mentions that 1% lidocaine solution can be used as a diluent for intramuscular injections 1. This practice is specifically supported in the CDC's sexually transmitted disease treatment guidelines, which note that "some health-care providers believe that the discomfort of the injection may be reduced by using 1% lidocaine solution as a diluent" 2.
Preparation and Stability
When mixing ceftriaxone with lidocaine:
- Use 1% lidocaine solution without epinephrine as the diluent 1
- Reconstituted ceftriaxone with lidocaine remains stable for:
- 24 hours at room temperature (25°C)
- 3 days when refrigerated (4°C) 1
Clinical Benefits
Research demonstrates clear benefits to using lidocaine as a diluent:
- Significantly reduces pain at the injection site compared to sterile water 3
- Pain reduction is observed immediately after injection and continues at 10-minute, 20-minute, and 6-hour intervals 3
- Does not alter the pharmacokinetics or bioavailability of ceftriaxone 4
A pharmacokinetic study showed that when ceftriaxone is mixed with 1% lidocaine:
- Peak plasma concentration remains similar (42 μg/ml vs 45 μg/ml with water)
- Elimination half-life is unchanged (7.0 hours vs 7.1 hours with water)
- Bioavailability is maintained (area under curve: 577 μg·h/ml vs 578 μg·h/ml with water) 4
Important Contraindications
Ceftriaxone mixed with lidocaine should NOT be administered:
- Intravenously (IV administration of ceftriaxone solutions containing lidocaine is contraindicated) 1
- To patients with known hypersensitivity to lidocaine 1
- In cases where any contraindications to lidocaine exist 1
Clinical Application
This mixture is particularly useful in outpatient and home parenteral therapy settings where patient comfort is important. A study of home parenteral therapy found that when lidocaine was used for reconstitution of ceftriaxone, the intramuscular route was well tolerated by all patients 5.
Dosing Considerations
For intramuscular administration of ceftriaxone with lidocaine:
- Use the following dilution ratios for 250 mg/mL concentration:
- 250 mg vial: add 0.9 mL of 1% lidocaine
- 500 mg vial: add 1.8 mL of 1% lidocaine
- 1 g vial: add 3.6 mL of 1% lidocaine
- 2 g vial: add 7.2 mL of 1% lidocaine 1
Best Practices for Administration
- Inject well within the body of a relatively large muscle
- Aspirate before injection to avoid unintentional injection into a blood vessel 1
- For pediatric patients, follow appropriate weight-based dosing guidelines 2
This practice of using lidocaine as a diluent for ceftriaxone is well-established, safe, and effective for reducing injection pain while maintaining the antimicrobial efficacy of ceftriaxone.