Rabies Immunoglobulin (RIG)

Risk has also been categorised as low in those animals that are healthy and can be observed versus high risk in those that are wild, unwell or can not be observed.

Human rabies immunoglobulin (HRIG) is taken from the plasma of immunised and screened human donors. Its aim is to reduce the risk after high risk exposure to rabies and give rapid protection until the rabies vaccine can become effective.

Administration:

• HRIG is dosed at 20 IU/kg and this should be infiltrated around the wound, any left over should be given intramuscularly in the anterolateral thigh, remote from the vaccination site.
• If more than 2ml is to be given in children or 5ml in adults the HRIG should be divided into smaller amounts and given at different sites.
• If equine RIG is the only immunoglobulin available the dose is 40 IU/kg, the risk of anaphylaxis and serum sickness is higher in this group but should not dissuade you from delivering appropriate treatment.
• If the calculated dose of RIG is insufficient to infiltrate all wounds, sterile saline may be used to dilute it 2 to 3 fold to permit thorough infiltration
• If the vaccine is given but HRIG is delayed it can still be given up to seven days after starting the course of the vaccine.

Contraindications or complications:

• None (safe in pregnancy and children)
• There is potential a risk of anaphylaxis and this should be administered in an area that can can monitor the patient and deliver adrenaline. The risk for anaphylaxis is higher if horse immunoglobulin is used.
• Serum Sickness: A benign and self limiting complication occurs 5-10 days after immunoglobulin, symptoms include fever, rash, arthralgia and myalgia. Oral steroids for 5 days may ameliorate symptoms (e.g. prednisolone 50mg/day in adults and 1mg/kg in children). All patients should be warned about this complication who receive immunoglobulin.

References

• The green book
• WHO guidelines (PEP prophylaxis – rabies 2014)