What is the recommended dose of rabies immunoglobulin (RIG) for post-exposure prophylaxis?

Rabies Immunoglobulin Dosing

The recommended dose of rabies immunoglobulin (RIG) for post-exposure prophylaxis is 20 IU/kg body weight, administered once at the initiation of treatment, with the full dose infiltrated around and into the wound(s) if anatomically feasible, and any remaining volume given intramuscularly at a site distant from vaccine administration. 1, 2, 3

Dosing Specifications

• The 20 IU/kg body weight formula is universally applicable across all age groups, including children, and applies to both human rabies immunoglobulin (HRIG) and equine rabies immunoglobulin (ERIG). 2

• This dose should be calculated based on total body weight, though the primary goal is wound infiltration rather than systemic administration. 1

Timing of Administration

• RIG must be administered as soon as possible after exposure, ideally at the time of the first vaccine dose (day 0). 3

• If not given initially, RIG can still be administered up to and including day 7 of the post-exposure prophylaxis series. 2

• Beyond day 7, RIG is contraindicated because an antibody response to the vaccine is presumed to have occurred, and RIG administration could interfere with this active immunity. 2

Administration Technique

The infiltration technique is critical for optimal protection:

• The full calculated dose should be thoroughly infiltrated in the area around and into all wounds, if anatomically feasible. 1, 2, 3

• Any remaining volume after wound infiltration should be administered intramuscularly at an anatomical site distant from vaccine administration (typically the deltoid muscle or lateral thigh, never the gluteal region due to sciatic nerve injury risk). 3

• This infiltration recommendation is based on rare reports of post-exposure prophylaxis failures when inadequate RIG was infiltrated at exposure sites. 2

Critical Safety Precautions

Several administration rules must be strictly followed:

• RIG should never be administered in the same syringe or at the same anatomical site as the rabies vaccine. 1, 2, 3

• Do not exceed the recommended 20 IU/kg dose, as RIG can partially suppress active antibody production from the vaccine. 1, 2, 3

• The gluteal region should not be used as an injection site due to risk of sciatic nerve injury. 3

Who Receives RIG

RIG is indicated only for previously unvaccinated persons:

• Unvaccinated individuals require both RIG and a 4-dose vaccine series (days 0,3,7, and 14) for both bite and non-bite exposures. 1, 2

• Immunocompromised patients still require a 5-dose vaccine schedule (days 0,3,7,14, and 28) in addition to RIG. 1, 2

• Previously vaccinated persons (those with documented prior complete vaccination) require only vaccine boosters on days 0 and 3, and should NOT receive RIG. 1, 2, 3

Common Pitfalls to Avoid

• Failing to infiltrate wounds adequately: The primary protective mechanism of RIG is local neutralization of virus at the exposure site, not systemic immunity. 2

• Administering RIG after day 7: This can interfere with vaccine-induced immunity without providing additional benefit. 2

• Giving RIG to previously vaccinated individuals: This is unnecessary and wastes resources, as these patients have immune memory. 1, 2

• Exceeding the recommended dose: More is not better with RIG, as excess can suppress the vaccine response. 1, 3

Safety Profile

• Adverse reactions to HRIG are uncommon, occurring in approximately 0.2-11% of recipients, and are typically mild (local pain, erythema, headache, fever). 4, 5

• All reported adverse events are transient and resolve without complications. 4, 5