What is the proper treatment and dosage of Rabies Immunoglobulin (RIG) for an individual exposed to rabies who has not been previously vaccinated?

Rabies Immunoglobulin (RIG) Treatment Protocol

Immediate Administration for Previously Unvaccinated Persons

For individuals exposed to rabies who have never been vaccinated, administer human rabies immunoglobulin (HRIG) at exactly 20 IU/kg body weight on day 0, ideally simultaneously with the first vaccine dose, infiltrating the full calculated dose thoroughly around and into all wounds if anatomically feasible, with any remaining volume injected intramuscularly at a site distant from vaccine administration. 1, 2, 3, 4, 5

Dosing Specifications

• Standard dose: 20 IU/kg body weight for all age groups, including children 2, 3, 4, 5
• Single administration: HRIG is given only once during the entire post-exposure prophylaxis (PEP) regimen 4
• Do not exceed the recommended dose: Higher amounts can suppress active antibody production from the vaccine 1, 4, 5
• Children receive the same weight-based dose (20 IU/kg) as adults 2, 4

Timing of Administration

• Optimal timing: Day 0 (the day the first vaccine dose is given), ideally within 24 hours of exposure 2, 3, 5
• Grace period: If not given on day 0, HRIG can still be administered up to and including day 7 of the vaccine series 1, 2, 4
• After day 7: HRIG is not indicated, as vaccine-induced antibody response is presumed to have occurred 4

Anatomical Administration Technique

Wound Infiltration (Critical Step)

• Primary route: Infiltrate the full calculated dose thoroughly around and into all wounds if anatomically feasible 1, 2, 3, 4, 5
• Rationale: Rare PEP failures have occurred when less than the full amount was infiltrated at exposure sites 4, 6
• Clinical reality: Only 56% of eligible patients receive proper wound infiltration in practice, representing a major adherence gap 7

Intramuscular Administration for Remaining Volume

• Site selection: Any remaining volume after wound infiltration should be injected intramuscularly at a site distant from vaccine administration 1, 2, 3, 4, 5
• Preferred sites: Deltoid muscle of the upper arm or lateral thigh muscle 5
• Avoid: Never use the gluteal region due to risk of sciatic nerve injury 5

Critical Administration Rules

• Never administer HRIG in the same syringe as the vaccine 1, 4, 5
• Never administer HRIG at the same anatomical site as the first vaccine dose 1, 2, 4, 5
• Subsequent vaccine doses (days 3,7,14) can be given in the same anatomic location where HRIG was previously administered 1

Complete PEP Regimen for Previously Unvaccinated Persons

Wound Care (First Step)

• Immediately wash all wounds thoroughly with soap and water for 15 minutes 2, 3, 5
• Irrigate with a virucidal agent such as povidone-iodine solution if available 1, 2, 3, 5

HRIG Administration

• 20 IU/kg body weight on day 0 as detailed above 1, 2, 3, 4, 5

Vaccine Schedule

• Standard 4-dose regimen: 1.0 mL intramuscularly on days 0,3,7, and 14 1, 2, 8
• Vaccine type: Human diploid cell vaccine (HDCV) or purified chick embryo cell vaccine (PCECV) 1, 2, 5
• Injection site: Deltoid muscle for adults and older children; anterolateral thigh for young children 1, 2, 5
• Never use gluteal area: This produces inadequate antibody response and is associated with vaccine failures 1, 2, 5

Special Populations

Immunocompromised Patients

• Modified vaccine schedule: 5-dose regimen on days 0,3,7,14, and 28 (not the standard 4-dose schedule) 1, 2, 4
• HRIG dose remains unchanged: Still 20 IU/kg on day 0 2, 3
• Mandatory serologic testing: Check rabies virus-neutralizing antibody titers 1-2 weeks after the final dose 2
• Rationale: Corticosteroids, immunosuppressive agents, antimalarials, and immunosuppressive illnesses substantially reduce vaccine response 2

Previously Vaccinated Persons

• HRIG is contraindicated: Do NOT administer HRIG to previously vaccinated individuals 1, 2, 3, 4, 5
• Rationale: HRIG will inhibit the anamnestic (memory) antibody response 1, 2
• Vaccine only: Give 2 doses of vaccine on days 0 and 3 1, 2, 5
• Definition of previously vaccinated: Anyone who completed a recommended pre-exposure or post-exposure vaccination regimen with cell-culture vaccines 1, 2

Common Clinical Pitfalls to Avoid

1. Administering HRIG to previously vaccinated persons: This is a critical error that suppresses the memory immune response 1, 2
2. Using the gluteal area for vaccine administration: Associated with vaccine failure due to inadequate immune response 1, 2, 5
3. Failing to infiltrate wounds with HRIG: Only 56% of eligible patients receive proper wound infiltration, yet this is essential for preventing rare PEP failures 7, 6
4. Exceeding the 20 IU/kg dose: Higher doses suppress active antibody production 1, 4, 5
5. Administering HRIG and vaccine in the same syringe or site: This violates fundamental administration principles 1, 4, 5
6. Delaying treatment while awaiting animal observation results: Initiate PEP immediately in rabies-endemic areas; treatment can be discontinued if the animal remains healthy after 10 days 2

Efficacy and Evidence Quality

• When administered properly, PEP is nearly 100% effective in preventing human rabies 2, 8
• The 4-dose vaccine schedule combined with HRIG is safe and effective for previously unvaccinated persons 8
• No case of human rabies in the United States has ever been attributed to receiving the complete vaccine course with appropriate HRIG administration 2
• High adherence rates in practice: 91% for patient selection, 98% for dosing, 100% for timing, but only 56% for proper wound infiltration 7