HRIG Dose for Bat Scratch in NSW
The recommended dose of human rabies immune globulin (HRIG) for a bat scratch in New South Wales is 20 IU/kg (0.133 mL/kg) body weight, administered once at the beginning of post-exposure prophylaxis. 1, 2
Dosing Details
The 20 IU/kg dose is:
- Universal across all age groups, including children 1
- Calculated based on total body weight
- Administered as a single dose only (never repeated) 1
Administration Technique
As much of the full calculated dose as anatomically feasible should be thoroughly infiltrated around and into the scratch wound(s). 1, 2 This local infiltration is critical—rare failures of post-exposure prophylaxis have been reported when insufficient HRIG was infiltrated at exposure sites 1.
Any remaining volume after wound infiltration should be administered intramuscularly at a site distant from the vaccine injection site 1, 2:
- Adults: deltoid muscle
- Children: lateral thigh muscle
- Never use the gluteal region (risk of sciatic nerve injury) 2
Critical Timing Considerations
- Ideally given on day 0 (same day as first vaccine dose) 2
- Can be administered up to and including day 7 of the vaccine series if not given initially 1
- Beyond day 7, HRIG is contraindicated because vaccine-induced antibody response is presumed to have occurred 1
Important Caveats
Do not exceed the recommended 20 IU/kg dose—excessive HRIG can partially suppress active antibody production from the vaccine 1. However, a recent case report suggests overdose may not cause adverse effects 3, though adherence to guidelines remains essential.
HRIG must never be:
- Administered in the same syringe as vaccine 1, 2
- Injected at the same anatomical site as the first vaccine dose 1
NSW-Specific Context
For minor bat exposures in NSW, post-exposure treatment may be delayed up to 48 hours while awaiting bat testing results 4. If the bat tests negative for Australian Bat Lyssavirus (ABLV), treatment can be withheld or discontinued 4. However, if treatment proceeds, the standard 20 IU/kg HRIG dose applies.
Vaccine Coadministration
HRIG is given alongside a 5-dose rabies vaccine series (days 0,3,7,14,28) for previously unvaccinated individuals 1, 2. Previously vaccinated individuals should NOT receive HRIG—they require vaccine only 1.