What is the recommended dose and administration of Rabies Immune Globulin (Rabies human monoclonal antibody) for a 20.8 kg child exposed to rabies?

Rabies Human Monoclonal Antibody Dosing for a 20.8 kg Child

For a 20.8 kg child exposed to rabies, administer 416 IU (approximately 2.77 mL) of human rabies immune globulin (HRIG) at 20 IU/kg body weight, infiltrating the full dose around and into the wound(s) if anatomically feasible, with any remaining volume given intramuscularly at a site distant from the rabies vaccine. 1

Dose Calculation

• The standard dose is exactly 20 IU/kg body weight for all age groups, including children 2, 3, 4, 1
• For this 20.8 kg child: 20 IU/kg × 20.8 kg = 416 IU total dose 1
• Using standard HRIG concentration of 150 IU/mL: 416 IU ÷ 150 IU/mL = 2.77 mL 2
• This will require two 2-mL vials (one full vial plus a partial second vial) 1

Administration Technique

Wound Infiltration (Primary Route)

• Infiltrate the full calculated dose (2.77 mL) thoroughly around and into all wounds if anatomically feasible 3, 4, 1
• This local infiltration is critical—rare failures of post-exposure prophylaxis have been reported when less than the full amount was infiltrated at exposure sites 4
• If the wound volume is insufficient to accommodate the full dose, dilution with normal saline may be necessary to provide adequate volume for complete wound infiltration 5

Intramuscular Administration (For Remaining Volume)

• Any remaining volume after wound infiltration should be injected intramuscularly at a site distant from vaccine administration 3, 4, 1
• For young children, use the anterolateral thigh for the intramuscular portion 3
• Never administer HRIG in the same syringe or at the same anatomical site as the rabies vaccine 3, 4, 1

Critical Timing

• Administer HRIG on day 0, ideally simultaneously with the first rabies vaccine dose 3, 4
• If not given on day 0, HRIG can still be administered up to and including day 7 after the first vaccine dose 3, 4
• Beyond day 7, do NOT administer HRIG—vaccine-induced antibody response is presumed to have occurred, and additional passive antibody may suppress active antibody production 4, 1

Dosing Precautions

• Do not exceed 20 IU/kg—higher doses can partially suppress active antibody production from the vaccine, potentially compromising protection 3, 4, 1, 6
• Discard any remaining product after drawing the calculated dose 1

Concurrent Rabies Vaccine Administration

• The child must also receive the 4-dose rabies vaccine series (1.0 mL intramuscularly on days 0,3,7, and 14) 3, 4
• For young children, administer vaccine in the anterolateral thigh (not deltoid, not gluteal area) 3
• Never use the gluteal area for vaccine administration—this produces inadequate antibody response and has been associated with vaccine failures 3
• Ensure vaccine and HRIG are given at separate anatomical sites 3, 1

Common Pitfalls to Avoid

• Failing to infiltrate wounds: The full dose should be infiltrated into/around wounds when possible—intramuscular administration alone is suboptimal 4, 7
• Exceeding the 20 IU/kg dose: This suppresses vaccine response 1, 6
• Administering HRIG and vaccine at the same site: This can interfere with vaccine efficacy 1
• Using the gluteal area for vaccine: This results in inadequate immune response 3
• Delaying HRIG beyond day 7: After day 7, HRIG should not be given 4

Safety Profile

• HRIG is well-tolerated with only 0.183% of patients reporting transient mild adverse reactions in large case series 8
• No serious allergic-type reactions were reported in controlled trials 7
• The combination of HRIG and vaccine is nearly 100% effective when administered promptly and appropriately 3