Lidocaine 1% Reconstitution for Intramuscular Ceftriaxone (Rocephin) 1g
Mix 3.6 mL of 1% lidocaine (without epinephrine) with Rocephin 1g powder for intramuscular injection, yielding a final concentration of approximately 250 mg/mL ceftriaxone. 1
FDA-Approved Reconstitution Protocol
The FDA label for ceftriaxone provides explicit instructions for intramuscular preparation using lidocaine as the diluent 1:
- For 1g vial: Add 3.6 mL of 1% lidocaine solution (without epinephrine) to achieve 250 mg/mL concentration 1
- Alternative concentration: Add 2.1 mL of 1% lidocaine solution to achieve 350 mg/mL concentration 1
- Technique: Inject diluent into vial, shake thoroughly to form solution, then withdraw entire contents 1
Critical Safety Considerations
Why Lidocaine WITHOUT Epinephrine
Use only plain 1% lidocaine solution without epinephrine for ceftriaxone reconstitution. 1 The FDA label specifically lists "1% Lidocaine Solution (without epinephrine)" as the appropriate diluent 1. While epinephrine is safe for local infiltrative anesthesia in most body sites 2, it is not indicated for antibiotic reconstitution and may affect drug stability.
Stability After Reconstitution
Once mixed with 1% lidocaine 1:
- Room temperature (25°C): Stable for 24 hours at both 100 mg/mL and 250-350 mg/mL concentrations 1
- Refrigerated (4°C): Stable for 10 days at 100 mg/mL; 3 days at 250-350 mg/mL 1
- Discard unused portions after these time periods 1
Injection Technique
Inject the reconstituted solution deep into a large muscle mass with aspiration before injection to avoid intravascular administration. 1 The FDA label emphasizes that "Ceftriaxone for Injection should be injected well within the body of a relatively large muscle; aspiration helps to avoid unintentional injection into a blood vessel" 1.
Common Pitfalls to Avoid
- Do not use diluents containing calcium (such as Ringer's solution or Hartmann's solution) as particulate formation can result 1
- Do not use lidocaine with epinephrine for reconstitution—only plain lidocaine is specified 1
- Do not exceed 24-hour room temperature stability even though the solution may appear clear 1
- Calculate total lidocaine dose if patient receives multiple injections, as maximum safe lidocaine dose is 4.5 mg/kg without epinephrine 3
Dosing Context
The standard adult dose of ceftriaxone is 1-2 grams daily, with a maximum of 4 grams per day 1. For uncomplicated infections, 1g is typically sufficient 1. The addition of lidocaine serves solely to reduce injection pain and does not affect the antibiotic's efficacy 1.