What is the post-exposure prophylaxis for an adult bitten by an animal suspected of carrying rabies, considering the patient's potential HIV status and immunosuppression?

Post-Exposure Prophylaxis for Rabies in Adults

Standard Regimen for Previously Unvaccinated Patients

For an adult bitten by an animal suspected of carrying rabies who has never received rabies vaccination, administer both human rabies immune globulin (HRIG) 20 IU/kg and a 4-dose rabies vaccine series (days 0,3,7,14) intramuscularly in the deltoid, regardless of HIV status or immunosuppression—with the critical exception that immunocompromised patients require a 5-dose vaccine series (days 0,3,7,14,28). 1, 2, 3

Immediate Wound Management

• Thoroughly wash all bite wounds immediately with soap and water for at least 5 minutes, as this alone markedly reduces rabies transmission risk in animal studies 1, 2
• Avoid suturing wounds when possible to allow drainage 1
• Administer tetanus prophylaxis and consider antibiotic prophylaxis based on wound characteristics 1

HRIG Administration Protocol

• Infiltrate the full 20 IU/kg dose of HRIG around and into the wound(s) if anatomically feasible, with any remaining volume injected intramuscularly at a site distant from vaccine administration 1
• Never administer HRIG in the same syringe or same anatomical site as the first vaccine dose, as this can interfere with active antibody production 1
• HRIG can be given up to and including day 7 of the vaccine series, but beyond day 7 it is contraindicated because active antibody response is presumed to have occurred 1, 2

Vaccine Administration

• Administer vaccine intramuscularly in the deltoid muscle only in adults—never use the gluteal area, as this has been associated with prophylaxis failures 1, 2
• The standard 4-dose schedule (days 0,3,7,14) is safe and effective when combined with HRIG 1, 3
• For immunocompromised patients (including those with HIV), use a 5-dose vaccine regimen (days 0,3,7,14,28) plus HRIG 2

Special Considerations for Immunosuppressed Patients

• Immunosuppressed persons should have their antibody titers checked after completing the vaccine series to confirm adequate seroconversion 1
• Failures to seroconvert should be managed in consultation with public health officials 1
• The 5-dose regimen provides additional protection for patients with impaired immune responses 2

Previously Vaccinated Patients

• If the patient has ever received complete pre-exposure or post-exposure rabies vaccination with a cell culture vaccine, give only 2 doses of vaccine (days 0 and 3) without HRIG 1, 2
• This simplified regimen works because previously vaccinated persons develop a rapid anamnestic immune response 1, 2

Critical Timing Considerations

• Rabies post-exposure prophylaxis is a medical urgency, not a medical emergency—initiate as soon as possible but treatment remains effective even if delayed by days, weeks, or months 1, 2
• The rabies incubation period can range from days to over 1 year, making delayed treatment still potentially life-saving 2
• Do not wait for laboratory confirmation of rabies in the animal before initiating prophylaxis if the exposure is high-risk 1

Risk Assessment by Animal Species

• All bites from wild carnivores (skunks, raccoons, foxes, coyotes) and bats must be considered rabies exposures requiring full prophylaxis unless the animal tests negative 1, 4
• For domestic dogs and cats that are healthy and available for observation, prophylaxis can be deferred while the animal is observed for 10 days 1, 4
• Bat exposures require special consideration—any physical contact with a bat warrants prophylaxis if a bite or mucous membrane contact cannot be excluded, as bat bites may be undetected 4
• Small rodent bites (rats, mice, squirrels, hamsters) almost never require prophylaxis, but consult local health departments before deciding 5, 4

Common Pitfalls to Avoid

• Never exceed the recommended HRIG dose of 20 IU/kg, as excess HRIG can suppress active antibody production 1
• Do not administer vaccine in the gluteal area in adults 1, 2
• Do not withhold prophylaxis based on time elapsed since exposure—rabies has an unpredictable incubation period 2
• For immunocompromised patients, do not use the standard 4-dose regimen—always use the 5-dose schedule 2

HIV-Specific Considerations

HIV status alone does not change the standard post-exposure prophylaxis regimen unless the patient is significantly immunosuppressed (CD4 count considerations should guide whether to use 4-dose vs 5-dose regimen). 2 Patients with advanced HIV/AIDS or those on immunosuppressive therapy should receive the 5-dose vaccine series with antibody titer confirmation afterward. 1, 2