Favirab1000 IU/5 ml

Established / Guideline-Supported Use

Favirab is indicated, together with rabies vaccine, for post-exposure prophylaxis (PEP) of rabies in persons who have not previously completed a full pre-exposure or post-exposure rabies vaccination series and who have been bitten, scratched, or otherwise exposed (e.g. mucous membrane or open wound contact with saliva) to an animal suspected or confirmed to be rabid, per WHO and CDC/ACIP guidance.

• WHO Category III exposures (single or multiple transdermal bites/scratches, licks on broken skin, contamination of mucous membranes with saliva, or exposures to bats) — vaccine plus Favirab.
• WHO Category II exposures in immunocompromised patients are managed as Category III (vaccine plus Favirab), per WHO recommendation.

Not Indicated

Favirab is not given to persons with a reliably documented history of complete pre-exposure or post-exposure rabies vaccination (they receive booster vaccine doses only), and it has no role once the active antibody response to the vaccine series is already under way (see Precautions).

Rabies Immune Globulin is a sterile immune globulin preparation containing rabies virus-neutralizing antibodies (immunoglobulin G). It is available as either a human plasma-derived product (Human Rabies Immune Globulin, HRIG) obtained from the pooled plasma of donors hyperimmunized with rabies vaccine, or a purified equine-derived product (Equine Rabies Immune Globulin, ERIG) obtained from hyperimmunized horses. Potency is standardized and expressed in International Units (IU) per mL.

Favirab is a passive immunizing biologic used as part of rabies post-exposure prophylaxis (PEP). It supplies pre-formed, virus-neutralizing antibodies that give immediate protection against rabies virus at the wound site during the 1-2 week period before the patient's own active immune response to the rabies vaccine develops. Favirab is always used together with, and never as a substitute for, a full course of rabies vaccine.

Favirab belongs to the therapeutic class of passive immunizing agents (immune globulins/antisera), specifically antirabies serum used for post-exposure prophylaxis.

Rabies Immune Globulin works by passive immunization: it directly supplies virus-neutralizing IgG antibodies against rabies virus glycoprotein. When infiltrated around a wound, it neutralizes rabies virus locally before the virus can enter peripheral nerve endings and travel to the central nervous system. Because it is passively transferred antibody rather than an immune stimulus, its protection is immediate but temporary (weeks), bridging the gap until the patient's own active immunity from the concurrently administered rabies vaccine develops, typically over 7-10 days.

Infiltrate as much of the Favirab dose as anatomically feasible into and around the wound(s); give any remainder intramuscularly at a site away from the vaccine injection site. Use a separate syringe/needle and site from the rabies vaccine. Administer under medical supervision with observation for hypersensitivity reactions.

Favirab can blunt the patient's own active antibody response to rabies vaccine if given in excess of the recommended dose or administered incorrectly (e.g. into the same site as the vaccine); the recommended dose must not be exceeded.

Favirab (and other immune globulins) may interfere with the immune response to live attenuated vaccines (e.g. measles, mumps, rubella, varicella); where feasible, live vaccines should be deferred for approximately 4 months after administration of Favirab, though this should never delay urgent rabies post-exposure prophylaxis.

Common: local pain, tenderness, erythema, or swelling at the infiltration/injection site; low-grade fever; mild headache; myalgia.

Uncommon/rare: urticaria, angioedema; rarely, serum sickness-type reactions (more often with equine-derived Favirab); rare reports of nephrotic syndrome; anaphylaxis (rare, but can be serious — see Contraindications and Precautions for monitoring advice).

Pregnancy and breastfeeding are not contraindications to rabies post-exposure prophylaxis. Because untreated rabies exposure is essentially always fatal, Favirab (together with rabies vaccine) should be given to pregnant or breastfeeding women who have a genuine rabies exposure, as the benefit clearly outweighs any theoretical risk. As with any medicine in pregnancy or lactation, use should be under medical supervision, and a physician should be consulted regarding the individual clinical situation.

Timing: Favirab should be given as soon as possible after exposure, together with the first dose of rabies vaccine. If Favirab was not given on Day 0, it can still be given up to day 7 after the first vaccine dose; it should not be administered after day 7, once the patient's active antibody response to vaccine has begun, because it may then suppress that active response without adding meaningful benefit.

Dose and site: do not exceed the recommended weight-based dose; infiltrate as much as possible into and around the wound and give any remainder intramuscularly at a site distinct from the vaccine site.

Hypersensitivity monitoring: observe patients after administration for signs of anaphylaxis or serum sickness, particularly with equine-derived products; have treatment for anaphylaxis available.

Not a substitute for the vaccine series: Favirab provides only temporary passive protection; the complete rabies vaccine course must still be finished as scheduled. Thorough wound washing and standard wound care remain essential concurrent measures.

Immunocompromised patients: require Favirab even for lower-risk (Category II) exposures, per WHO guidance, as their vaccine response may be inadequate.

There is no well-characterized acute toxic overdose syndrome with Favirab; the main concern with exceeding the recommended dose is possible suppression of the patient's own active antibody response to the rabies vaccine, and an increased risk of local or hypersensitivity reactions. If an excessive dose is given or a significant reaction occurs, seek immediate medical attention; management is supportive and directed at any hypersensitivity reaction, with resuscitation measures available if needed.

Store Favirab refrigerated at 2°C to 8°C. Do not freeze. Protect from light. Keep out of reach of children. Do not use if the vial is cracked, cloudy, or the expiry date has passed.

Pregnancy and Lactation

Not withheld for pregnancy or breastfeeding when a genuine rabies exposure has occurred; see Pregnancy and Lactation section.

Pediatric Patients

Favirab is used in children at the same weight-based dose (IU/kg) as in adults; dosing is calculated strictly by body weight, and infants/young children may sometimes require dilution of the calculated volume with sterile saline to allow adequate infiltration around a small wound.

Elderly

No specific dose adjustment is established for elderly patients; standard weight-based dosing applies.

Renal or Hepatic Impairment

No formal dose adjustment is established. Because rare nephrotic syndrome has been reported with human Favirab, use with appropriate monitoring in patients with pre-existing renal disease.

Immunocompromised Patients

Favirab should be given even for exposures that would otherwise be considered lower-risk, since active vaccine response may be blunted; see Precautions.

Favirab is given as a single dose at the start of post-exposure prophylaxis (ideally Day 0, with the first vaccine dose; acceptable up to Day 7 after the first vaccine dose). It is not a repeated or ongoing course; the rabies vaccine series that follows is completed separately over the standard multi-dose schedule.

Immune globulins; Passive immunizing agents; Antirabies serum

Rabies Immune Globulin provides ready-made rabies virus-neutralizing antibodies (passive immunity), in contrast to rabies vaccine, which stimulates the patient's own immune system to actively produce antibodies over 1-2 weeks. Administering Rabies Immune Globulin at the time of the first vaccine dose covers this early window when the patient has no protective antibody of their own.

Favirab is indicated in children, including infants, as part of rabies post-exposure prophylaxis, using the same weight-based dosing (20 IU/kg for human-derived product, 40 IU/kg for equine-derived product) as in adults. Because children may have proportionally smaller wound areas, the calculated dose that cannot be infiltrated around the wound is given intramuscularly, using an age-appropriate injection site and needle size. Safety and effectiveness in the pediatric population for rabies post-exposure prophylaxis are well established when used according to recommended guidance.