How to prescribe rabies immunoglobulin
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rabies immunoglobulin post-exposure prophylaxis
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Prescribing Rabies Immunoglobulin (RIG)
What is RIG and Why It's Used
Rabies immunoglobulin (RIG) provides passive immunization - it delivers pre-formed antibodies that inhibit viral spread immediately, bridging the gap until the patient generates their own active immunity from the rabies vaccine (which takes ~7 days). It is given only once as part of post-exposure prophylaxis (PEP).
Step 1 - Determine if RIG is Indicated
RIG is required for previously unvaccinated patients with:
| WHO Category | Exposure Type | Action |
|---|---|---|
| Category I | Touch/feed animal, licks on intact skin | No PEP needed |
| Category II | Nibbling of uncovered skin, minor scratches without bleeding | Vaccine only |
| Category III | Transdermal bite(s), scratches with bleeding, licks on broken skin/mucosa, bat exposure | Vaccine + RIG |
- RIG is NOT given to patients who have previously completed a full rabies vaccination course (they should receive 2 booster vaccine doses on days 0 and 3 only - no RIG).
- In US practice, RIG is given for all PEP in previously unvaccinated persons.
Step 2 - Choose the Type of RIG
| Type | Dose | Notes |
|---|---|---|
| Human RIG (HRIG) | 20 IU/kg body weight | Preferred; e.g., HyperRAB (Grifols); fewer adverse reactions |
| Equine RIG (ERIG) | 40 IU/kg body weight | Used when HRIG unavailable; purified F(ab')2 products are safe; rare anaphylaxis risk (~1 in 45,000) |
| Monoclonal antibodies | Per product labeling | Alternative when RIG unavailable |
Skin testing before ERIG is not recommended - it does not predict reactions and RIG should be given regardless of the result. Have epinephrine ready for anaphylaxis.
Step 3 - Timing
- Administer RIG as soon as possible after exposure, ideally on Day 0 (same day as the first vaccine dose).
- RIG can be given up to Day 7 after the first vaccine dose.
- After Day 7: do NOT give RIG - active antibody response is presumed to have occurred by then, and RIG may interfere with it.
Step 4 - How to Administer RIG
- Calculate the dose by body weight (HRIG: 20 IU/kg; ERIG: 40 IU/kg).
- Infiltrate as much as anatomically possible directly into and around the wound site(s). This is the most important step - local infiltration neutralizes virus at the entry point.
- If the wound is a small puncture where full volume cannot be injected, dilute the RIG with normal saline to achieve a volume sufficient to infiltrate all wound sites.
- Any remaining RIG (if volume exceeds what the wound can absorb) is injected intramuscularly at a site distant from the vaccine injection site (e.g., if vaccine goes in the deltoid, give remaining RIG in the thigh or gluteal region).
- Do not inject the vaccine and RIG in the same syringe or at the same anatomical site - they must be separate.
- Avoid injecting into a finger or toe to prevent compartment syndrome.
Step 5 - Vaccine Regimen (given alongside RIG on Day 0)
For previously unvaccinated patients, RIG is always combined with the vaccine series. Common regimens:
| Regimen | Schedule | Route |
|---|---|---|
| Essen (5-dose) | Days 0, 3, 7, 14, 28 | IM (deltoid; or anterolateral thigh in children <2 yr) |
| Zagreb (4-dose, 2-1-1) | Days 0 (×2 sites), 3, 7, 21 | IM |
| 4-dose (WHO, immunocompetent) | Days 0, 3, 7, 14 | IM |
| 2-site intradermal | Days 0, 3, 7, 28 | ID 0.1 ml per site |
For immunocompromised patients (HIV/AIDS, on corticosteroids, etc.): use the full 5-dose IM regimen and consider checking rabies virus neutralizing antibody 2-4 weeks after the last dose (target: >0.5 IU/mL).
Adverse Effects of RIG
- HRIG: Local pain, induration, swelling, erythema (30-100% of injections); headache is the most common systemic effect (>50%); no deaths reported.
- ERIG: Similar local reactions; rare anaphylaxis (~1/45,000); no skin test required but always prepare for anaphylaxis management.
Key Points Summary
- RIG is a one-time only dose - never repeat it.
- Wound infiltration is the priority - pour as much as possible into the wound.
- Give it within 7 days of first vaccine dose; never after that.
- No RIG for previously vaccinated individuals.
- HRIG dose = 20 IU/kg; ERIG dose = 40 IU/kg.
- Keep vaccine and RIG in separate syringes and separate sites.
Sources:
- Park's Textbook of Preventive and Social Medicine - Rabies immunoglobulin section, pp. 324-325
- Rosen's Emergency Medicine, 9th ed. - Rabies Management, p. 2626
- Medical Microbiology 9e - Rhabdovirus Treatment and Prophylaxis, p. 566
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