How should human rabies immune globulin (HRIG) be administered by wound infiltration?

How to Administer HRIG by Wound Infiltration

The full calculated dose of HRIG (20 IU/kg or 0.133 mL/kg) should be thoroughly infiltrated directly into and around all wound sites if anatomically feasible, with any remaining volume given intramuscularly at a site distant from the vaccine administration. 12

Dosing Calculation

• Calculate the total HRIG dose: 20 IU/kg body weight (0.133 mL/kg)
• This formula applies to all ages, including children 11
• Do not exceed the recommended dose, as HRIG can partially suppress active antibody production 1

Infiltration Technique

Primary Goal: Wound Infiltration

Infiltrate as much of the calculated dose as anatomically feasible directly into and around the wound(s). This is critical because rare failures of postexposure prophylaxis have been reported when less than the full amount was infiltrated at exposure sites 11.

Step-by-Step Approach:

1. Cleanse the wound thoroughly with soap and water before infiltration 1
2. Inject HRIG slowly into the wound edges and surrounding tissue - infiltrate the area around and into the wounds 12
3. Use the full calculated dose for infiltration when possible - prioritize getting antibody directly to the exposure site
4. Any remaining volume after maximal wound infiltration should be given IM in the deltoid (adults) or anterolateral thigh (children) 12

Volume Guidelines by Wound Size

Recent evidence suggests practical volumes for infiltration based on wound size 3:

• <1 cm wound: approximately 1 mL
• 1-5 cm wound: approximately 3 mL
• >5 cm wound: approximately 5 mL

Critical Anatomical Considerations

Sites Requiring Caution:

• Face/head wounds: Infiltration occurs less frequently here but should still be attempted when safe 4
• Hand/finger wounds: More challenging to infiltrate but essential given high-risk location 4
• Multiple wounds: Distribute the HRIG proportionally among all wounds 1

Absolute Contraindications for IM Portion:

• Never use the gluteal region - risk of sciatic nerve injury 2
• Never administer in the same syringe or anatomical site as the vaccine 12

Common Pitfalls to Avoid

1. Insufficient wound infiltration: Only 56% of eligible patients receive proper wound infiltration in practice 5. This is the most common error and increases prophylaxis failure risk.

2. Administering IM only without attempting infiltration: Even difficult wounds (abrasions, small punctures) should receive infiltration attempts 4

3. Delaying HRIG administration: Give at the time of first vaccine dose (day 0), but can be given up to day 7 12. Beyond day 7, do not give HRIG as vaccine-induced antibodies are presumed present.

4. Giving HRIG to previously vaccinated individuals: Those with documented prior complete rabies vaccination series should receive vaccine only, not HRIG 11

Timing

• Administer HRIG once only at the beginning of prophylaxis 11
• Preferably given simultaneously with the first vaccine dose
• Can be administered through day 7 after first vaccine dose if initially missed 12
• After day 7: Do not give HRIG - antibody response to vaccine is presumed 1

Safety Profile

Adverse events are mild (11.4% incidence) and include local pain, erythema, itching, headache, and fever - all self-limited 6. No cases of compartment syndrome or nerve injury have been reported with proper administration technique 7.