Rabies Immunoglobulin Dosage
The recommended dose of rabies immunoglobulin (RIG) for post-exposure prophylaxis is exactly 20 IU/kg body weight, administered once at the beginning of treatment, with the full calculated dose infiltrated around and into all wounds if anatomically feasible. 1, 2, 3
Standard Dosing Protocol
Administer 20 IU/kg body weight as a single dose - this applies universally to all age groups including children, and is the standard for both human rabies immunoglobulin (HRIG) and equine rabies immunoglobulin (ERIG). 1, 2, 3
Never exceed the recommended 20 IU/kg dose, as higher doses can partially suppress active antibody production from the vaccine, potentially compromising protection. 1, 2, 4, 3
The 20 IU/kg dosing was established through clinical trials that demonstrated 40 IU/kg interfered with optimal vaccine-induced antibody production, while 20 IU/kg provided adequate passive immunity without significant interference. 5
Timing of Administration
RIG should ideally be given simultaneously with the first vaccine dose on day 0 to provide immediate passive immunity while the body begins producing its own antibodies. 2, 4, 3
If not given on day 0, RIG can still be administered up to and including day 7 of the vaccine series. 2, 4, 3
Beyond day 7, do not administer RIG because an antibody response to the vaccine is presumed to have occurred by that time, making passive immunization unnecessary. 2, 4
Administration Technique
Infiltrate the full calculated dose thoroughly in the area around and into all wounds if anatomically feasible - this is critical because rare failures of post-exposure prophylaxis have been reported when less than the full amount was infiltrated at exposure sites. 1, 2, 3
Any remaining volume after wound infiltration should be administered intramuscularly at a site distant from vaccine administration (typically the deltoid muscle or lateral thigh, never the gluteal region). 1, 2, 3
Never administer RIG in the same syringe, needle, or anatomical site as the vaccine because this may interfere with vaccine immunogenicity. 1, 2, 4, 3
Critical Contraindications
- Do not give RIG to previously vaccinated persons - individuals with a documented history of complete pre-exposure or post-exposure vaccination with cell culture vaccines require only a 2-dose vaccine booster (days 0 and 3) without RIG, as the immunoglobulin will inhibit their anamnestic antibody response. 1, 2, 4, 3
Vaccine Schedule Considerations
For previously unvaccinated immunocompetent persons, RIG is combined with a 4-dose vaccine schedule on days 0,3,7, and 14. 1, 2, 4
For immunocompromised patients, use a 5-dose vaccine schedule on days 0,3,7,14, and 28 along with the standard 20 IU/kg RIG dose. 1, 2, 4
Common Pitfalls to Avoid
Avoid the gluteal region for any injections (both RIG and vaccine) due to risk of sciatic nerve injury and inadequate antibody response. 4, 3
Do not use abbreviated vaccine schedules (such as the 2-1-1 regimen) when RIG is administered - studies demonstrate that RIG suppresses vaccine immunogenicity with these shortened schedules, with HRIG showing more pronounced suppression than ERIG, resulting in suboptimal seroconversion rates. 6, 7
Calculate the exact dose based on current body weight - underdosing may provide inadequate passive protection, while overdosing suppresses active antibody production. 1, 2, 3