Rabies Immunoglobulin Dosing for Post-Exposure Prophylaxis

Administration Guidelines

• The Centers for Disease Control and Prevention recommends a dose of 20 IU/kg body weight of rabies immunoglobulin for post-exposure prophylaxis, applicable to all age groups including children 1, 2, 3
• The 20 IU/kg body weight formula is standard for both human rabies immunoglobulin and equine rabies immunoglobulin 1, 2, 4
• Rabies immunoglobulin should be administered only once at the beginning of post-exposure prophylaxis to provide immediate passive immunity 2, 3
• If not administered at the start of vaccination, rabies immunoglobulin can still be given up to and including day 7 of the post-exposure prophylaxis series 1, 3
• Beyond day 7, rabies immunoglobulin is not indicated as an antibody response to the vaccine is presumed to have occurred 2, 4

Administration Technique

• The full dose of rabies immunoglobulin should be thoroughly infiltrated in the area around and into the wounds, if anatomically feasible 2, 5
• Any remaining volume should be injected intramuscularly at a site distant from vaccine administration 3
• This infiltration recommendation is based on reports of rare failures of post-exposure prophylaxis when less than the full amount of rabies immunoglobulin was infiltrated at exposure sites 1, 2

Important Precautions

• Rabies immunoglobulin should never be administered in the same syringe or in the same anatomical site as the first vaccine dose 1, 2
• Because rabies immunoglobulin can partially suppress active production of antibody, the dose administered should not exceed the recommended dose 2, 3

Vaccination Schedule

• For previously unvaccinated persons, the current recommendation is a 4-dose vaccine schedule along with rabies immunoglobulin 5, 6, 7
• For immunocompromised patients, the 5-dose schedule is still recommended 5, 6
• Persons who have previously received complete rabies vaccination require only vaccine and no rabies immunoglobulin 2, 5

Clinical Considerations

• The combination of rabies immunoglobulin and vaccine is recommended for both bite and non-bite exposures reported by previously unvaccinated persons 1, 2
• If post-exposure prophylaxis has been initiated and appropriate laboratory testing confirms the animal was not rabid, prophylaxis can be discontinued 1, 3
• Proper wound cleansing with soap and water and a virucidal agent is an essential component of rabies prevention 3, 4

Human Rabies Immune Globulin (HRIG) Dosing and Administration Guidelines

Recommended Dose Calculation

• For a patient weighing 80 kg, the CDC recommends a total HRIG dose of 20 IU per kilogram, resulting in 1,600 IU (≈10.6 mL using the standard 150 IU/mL concentration) 8.
• The calculated dose is typically assembled from five 2‑mL vials (300 IU each) plus a partial sixth vial to achieve the full 1,600 IU amount 8.

Administration Technique

• The entire calculated HRIG volume should be infiltrated around and into all wounds whenever anatomically feasible; any remaining volume must be injected intramuscularly at a site distant from the rabies vaccine injection 8.
• HRIG must never be administered in the same syringe or at the same anatomical site as the rabies vaccine, because co‑administration interferes with the active antibody response 8.
• The dose must not exceed 20 IU/kg; higher doses have been shown to partially suppress the vaccine‑induced antibody response and may compromise protection 8.

Timing of HRIG Administration

• HRIG should be given on day 0, ideally at the same time as the first rabies vaccine dose 8.
• If the initial dose is missed, HRIG may still be administered up to and including day 7 after the first vaccine dose; administration after day 7 is not recommended because vaccine‑induced antibodies are presumed to have developed and additional passive antibody could suppress the active response 8.

Common Implementation Gaps

• A 2020 multi‑hospital study reported that while 98 % of patients received the correct HRIG dose within the appropriate timeframe, only 56 % of eligible patients received wound infiltration as recommended, highlighting a frequent error that may reduce prophylactic effectiveness 8.

*All recommendations are based on CDC expert consensus (MMWR Recommendations and Reports, 2008).

Rabies Immune Globulin (HRIG) Dosing and Administration Guidelines

Dose Determination

• The recommended HRIG dose is 20 IU per kilogram of body weight, calculated by multiplying the patient’s weight (kg) by 20 IU; this applies to all age groups, including infants, children, and adults【9】【10】.
• The dose calculation formula (weight (kg) × 20 IU = total IU) should be used universally for every patient receiving HRIG【9】【10】.

Administration Technique

• The entire calculated HRIG dose must be infiltrated around and into all bite wounds whenever anatomically feasible【9】.
• Any remaining HRIG volume after wound infiltration should be given intramuscularly at a site distant from the rabies vaccine injection site【9】.
• HRIG must never be administered in the same syringe or at the same anatomical site as the rabies vaccine, because co‑administration interferes with active antibody production【9】【10】.

Dosing Limits

• Do not exceed 20 IU/kg; doses higher than this have been shown to partially suppress the vaccine‑induced antibody response and may compromise protection【9】【10】.

Timing of Administration

• HRIG should be administered on day 0, ideally at the same time as the first rabies vaccine dose【9】.
• If HRIG is not given on day 0, it may still be administered up to and including day 7 after the first vaccine dose【9】【10】.
• HRIG should not be given after day 7, because vaccine‑induced antibodies are presumed to have developed and additional passive antibody may suppress the active immune response【9】【10】.

Special Population Considerations

• Individuals previously vaccinated against rabies should not receive HRIG; they require only vaccine doses on days 0 and 3, as HRIG would inhibit the anamnestic antibody response【9】【10】.

Clinical Implications of Improper Administration

• Failure to infiltrate wounds with the full calculated HRIG dose has been linked to rare failures of post‑exposure prophylaxis, underscoring the importance of complete wound infiltration【9】.