What is the recommended treatment and dosage of rabies immunoglobulin (RIG) for an individual exposed to rabies, possibly through an animal bite?

Rabies Immunoglobulin (RIG) for Post-Exposure Prophylaxis

Immediate Treatment Protocol

For previously unvaccinated individuals exposed to rabies through an animal bite or other high-risk exposure, administer rabies immune globulin (RIG) at 20 IU/kg body weight as a single dose on day 0, infiltrating as much as anatomically feasible into and around all wounds, with any remaining volume given intramuscularly at a site distant from the vaccine injection, combined with a 4-dose rabies vaccine series on days 0,3,7, and 14. 1, 2, 3

Essential First Steps

• Wound washing is the single most critical intervention and must be performed immediately—scrub all bite wounds and scratches thoroughly with soap and water for approximately 15 minutes, followed by irrigation with povidone-iodine solution 4, 5, 6
• This local wound cleansing alone markedly reduces rabies transmission risk in animal studies and should never be delayed 4, 2
• Assess for tetanus prophylaxis and bacterial infection control as clinically indicated 4

RIG Administration Guidelines

Dosing and Timing

• RIG dose is 20 IU/kg body weight, given once only on day 0 2, 3
• If RIG was not given on day 0, it can still be administered up to and including day 7 after the first vaccine dose 4, 1, 2
• Beyond day 7, RIG is contraindicated because active antibody production from the vaccine series has begun, and RIG can partially suppress this response 4, 1, 2
• Never exceed the recommended dose, as excess RIG suppresses active antibody production 4, 5

Anatomical Administration

• Infiltrate the full calculated RIG dose into and around all wounds whenever anatomically feasible—this provides immediate local passive immunity at the exposure site 2, 3
• Any remaining RIG volume after wound infiltration should be administered intramuscularly at a site distant from the vaccine injection site 2, 3
• A 2020 study found only 56% adherence to wound infiltration guidelines despite 98% correct dosing, representing a critical gap in optimal PEP delivery 7

Vaccine Regimen

Previously Unvaccinated Persons

• Administer 4 doses of rabies vaccine intramuscularly on days 0,3,7, and 14 (this is the current CDC-recommended schedule) 1
• Give vaccine in the deltoid muscle in adults or anterolateral thigh in young children 4
• Never administer vaccine in the gluteal area—this route has been associated with treatment failures due to lower neutralizing antibody titers 4, 1

Previously Vaccinated Persons

• Give only 2 doses of vaccine on days 0 and 3, without RIG—these individuals mount a rapid anamnestic immune response 1, 3
• This applies to anyone who completed a full pre-exposure or post-exposure vaccination series with a cell culture vaccine 4

Immunocompromised Persons

• Use a 5-dose vaccine regimen on days 0,3,7,14, and 28 plus RIG for immunocompromised individuals 1

Critical Timing Considerations

• Initiate PEP immediately after exposure, ideally within 24 hours, though this is a medical urgency rather than emergency 4, 8, 2
• PEP should be given regardless of delay from exposure—even if months have passed—as long as clinical rabies symptoms have not appeared 4, 1, 8
• Rabies incubation periods typically range from 2-6 weeks but can exceed 1 year in humans 4, 8
• Once clinical signs of rabies develop, PEP is ineffective and the disease is universally fatal 8

Animal Observation Protocols

• Healthy domestic dogs, cats, or ferrets can be confined and observed for 10 days 4, 5, 2
• If the animal remains healthy throughout the 10-day period, no PEP is needed—dogs do not shed rabies virus in saliva more than 10 days before showing clinical signs 1, 5
• Initiate PEP immediately if the animal: dies during observation, develops illness or signs suggestive of rabies, is stray/unwanted and cannot be observed, or is a high-risk wild species (skunk, bat, fox, coyote, raccoon) 4, 5, 2
• For wild carnivores and bats, regard as rabid unless proven negative by laboratory testing 2

Common Pitfalls to Avoid

• Failing to infiltrate wounds with RIG—only 56% of eligible patients receive proper wound infiltration despite this being a guideline recommendation 7
• Administering RIG beyond day 7—this suppresses the active immune response without benefit 4, 1
• Exceeding the 20 IU/kg RIG dose—excess RIG interferes with vaccine-induced antibody production 4, 5, 2
• Giving vaccine in the gluteal area—this has been associated with PEP failures 4, 1
• Delaying treatment while awaiting animal testing results when high-risk exposure has occurred 8
• Inadequate wound cleansing—this simple measure alone significantly reduces transmission risk 4, 5

Safety and Efficacy Evidence

• A 2022 prospective study of 123 patients receiving HRIG with full vaccination demonstrated 100% survival at 6 months with only 11.4% experiencing mild, self-limited adverse events (local pain, erythema, headache, fever) 9
• A 2020 multi-hospital study showed 91% adherence to RIG patient selection, 98% correct dosing, and 100% appropriate timing within 7 days 7
• The combination of RIG and modern cell culture vaccines provides near 100% protection when administered correctly and promptly 4, 2, 10

Special Circumstances

• For exposures outside the United States in canine rabies-endemic areas, some authorities recommend initiating PEP immediately, which can be discontinued if the dog remains healthy for 10 days 4
• Unprovoked attacks are more likely to indicate rabies than provoked attacks (e.g., attempting to feed or handle an animal) 4
• A fully vaccinated dog or cat is unlikely to become infected, though rare breakthrough cases have been reported 4, 5