Minimum Reconstitution Volume for 1gm Rocephin IM Injection
For 1 gram of Rocephin (ceftriaxone) administered intramuscularly, the minimum recommended reconstitution volume is 2.1 mL, which yields a concentration of 350 mg/mL. 1
Reconstitution Guidelines for IM Administration
According to the FDA drug label for ceftriaxone, the following reconstitution volumes are recommended for intramuscular administration:
| Vial Dosage Size | Amount of Diluent for 250 mg/mL | Amount of Diluent for 350 mg/mL |
|---|---|---|
| 500 mg | 1.8 mL | 1.0 mL |
| 1 g | 3.6 mL | 2.1 mL |
| 2 g | 7.2 mL | 4.2 mL |
Appropriate Diluents for Reconstitution
When reconstituting ceftriaxone for IM injection, the following diluents can be used 1:
- Sterile Water for Injection
- 0.9% Sodium Chloride Solution
- 5% Dextrose Solution
- Bacteriostatic Water + 0.9% Benzyl Alcohol
- 1% Lidocaine Solution (without epinephrine)
Important Clinical Considerations
Injection Technique
- Ceftriaxone should be injected well within the body of a relatively large muscle
- Aspiration before injection helps avoid unintentional injection into a blood vessel 1
Stability After Reconstitution
When reconstituted for IM administration, ceftriaxone remains stable (less than 10% loss of potency) for the following time periods 1:
| Diluent | Concentration | Room Temperature (25°C) | Refrigerated (4°C) |
|---|---|---|---|
| Sterile Water for Injection | 250,350 mg/mL | 24 hours | 3 days |
| 0.9% Sodium Chloride Solution | 250,350 mg/mL | 24 hours | 3 days |
| 5% Dextrose Solution | 250,350 mg/mL | 24 hours | 3 days |
| Bacteriostatic Water + 0.9% Benzyl Alcohol | 250,350 mg/mL | 24 hours | 3 days |
| 1% Lidocaine Solution (without epinephrine) | 250,350 mg/mL | 24 hours | 3 days |
Contraindications and Precautions
- Do not use diluents containing calcium, such as Ringer's solution or Hartmann's solution, to reconstitute ceftriaxone as particulate formation can result 1
- Ceftriaxone is contraindicated in neonates (≤28 days) if they require calcium-containing IV solutions due to risk of precipitation 1
Clinical Pharmacokinetics
After intramuscular administration of 1g ceftriaxone, mean peak plasma concentrations reach approximately 81 μg/mL 2. The drug is rapidly and completely absorbed following IM administration, with plasma concentrations becoming equivalent to IV administration by 2.5 hours post-dose 2, 3.
The long elimination half-life (7.6-8.3 hours) of ceftriaxone allows for once-daily dosing in most clinical scenarios 2, 3.