What volume of 1% lidocaine should be added to a 500 mg vial of Rocephin (ceftriaxone) for intramuscular injection in a 21‑month‑old child?

Lidocaine Reconstitution for Intramuscular Ceftriaxone in a 21-Month-Old

Mix 500 mg Rocephin (ceftriaxone) with 1.8 mL of 1% lidocaine for intramuscular injection in your 21-month-old patient.

Reconstitution Protocol

The standard reconstitution for IM ceftriaxone uses 1% lidocaine at approximately 1.8 mL per 500 mg vial to create a final concentration suitable for deep intramuscular injection. 1

Step-by-Step Preparation

• Draw up 1.8 mL of 1% lidocaine hydrochloride injection into a syringe 1
• Inject the lidocaine into the 500 mg ceftriaxone vial 1
• Shake the vial vigorously until the powder is completely dissolved and the solution is clear to pale yellow 1
• Administer the reconstituted solution within 1 hour of preparation to maintain stability 1
• Inject deep into a large muscle mass such as the gluteal muscle or lateral thigh 1

Rationale for Lidocaine Use

• Lidocaine significantly reduces injection site pain, which is particularly important in pediatric patients because IM ceftriaxone injections are notably painful 2, 1
• The American Heart Association explicitly recommends counseling families that IM ceftriaxone is painful, making lidocaine reconstitution a practical pain-reduction strategy 2

Safety Considerations

Contraindications to Lidocaine

• Do not use lidocaine if the child has a known hypersensitivity to amide-type local anesthetics 1
• Lidocaine is contraindicated in complete heart block 1

Monitoring

• Observe the injection site for signs of inflammation or infection after administration 1
• Be aware that lidocaine can cause cardiac arrhythmias, myocardial depression, and seizures at high concentrations, though this is rare at the doses used for reconstitution 1

Dosing Context for This Patient

For a 21-month-old child, the typical ceftriaxone dose is 50–75 mg/kg/day for most infections, given once daily or divided every 12–24 hours 2. A 500 mg dose is appropriate for a child weighing approximately 7–10 kg, which is within the expected range for this age 2.

Common Pitfalls to Avoid

• Never exceed 1 hour between reconstitution and administration, as stability decreases 1
• Do not use discolored solution or solution with visible particulates 1
• Ensure the powder is completely dissolved before drawing up the dose 1
• For doses exceeding 1 gram (not applicable here), divide between different injection sites 1