Rabies Immunoglobulin Dosing
The recommended dose of rabies immunoglobulin is 20 IU/kg body weight for human rabies immunoglobulin (HRIG) or 40 IU/kg body weight for equine rabies immunoglobulin (ERIG), administered once on day 0 of post-exposure prophylaxis. 1, 2
Administration Details
Dosing by Product Type
- Human Rabies Immunoglobulin (HRIG): 20 IU/kg body weight (equivalent to 0.133 mL/kg) 2
- Equine Rabies Immunoglobulin (ERIG): 40 IU/kg body weight 3
The dose applies to all age groups, including children—there is no adjustment needed for pediatric patients 1.
Timing of Administration
Rabies immunoglobulin must be given on day 0 (the same day as the first vaccine dose) when initiating post-exposure prophylaxis. If not administered on day 0, it can still be given up to and including day 7 after the first vaccine dose 1, 2. Beyond day 7, RIG should not be administered as the patient should be producing their own antibodies from vaccination.
Anatomical Site and Technique
If anatomically feasible, infiltrate the full calculated dose around and into the wound(s). Any remaining volume after wound infiltration should be administered intramuscularly at a site distant from the vaccine injection 1, 2.
A real-world study found that only 56% of eligible patients actually received proper wound infiltration, representing a significant gap in adherence to guidelines 4. This is a critical error to avoid, as local wound infiltration provides immediate passive immunity at the exposure site.
For the intramuscular portion:
- Use the deltoid muscle in adults
- Use the lateral thigh muscle in children
- Never use the gluteal region due to risk of sciatic nerve injury 2
Critical Pitfalls to Avoid
Do Not Exceed the Recommended Dose
Never administer more than the recommended dose of RIG. Excessive RIG can suppress the active antibody production induced by the vaccine 1. While one case report showed no adverse effects from HRIG overdose 5, the guideline recommendation remains firm on this point to avoid potential immune suppression.
Separate from Vaccine Administration
- Never administer RIG in the same syringe as the vaccine 1, 2
- Never inject RIG at the same anatomical site as the first vaccine dose 1, 2
- Subsequent vaccine doses (days 3,7,14) can be given in the same location where RIG was previously administered 1
Patient Selection
RIG is only indicated for previously unvaccinated persons. Do not administer RIG to individuals with a documented history of:
- Pre-exposure rabies vaccination
- Prior post-exposure prophylaxis with rabies vaccine
- Documented antibody response to previous rabies vaccination 1
These previously vaccinated individuals receive only vaccine (2 doses on days 0 and 3) without RIG 1.
Product Considerations
While HRIG at 20 IU/kg is the standard in the United States 1, 2, purified equine RIG (ERIG) at 40 IU/kg is an acceptable alternative, particularly in resource-limited settings where it may be more available and less expensive 3. Studies demonstrate that ERIG produces adequate antibody levels and has comparable safety profiles when properly purified and heat-treated 3.