Acyclovir Dosing for Herpes B Virus Prophylaxis After Monkey Bite
For prophylaxis against herpes B virus following a monkey bite, oral acyclovir should be administered at a dose of 800 mg five times daily (every 4 hours while awake) immediately after exposure. 1, 2
Rationale and Evidence
The management of potential herpes B virus (Herpesvirus simiae) exposure from monkey bites requires immediate intervention due to the high mortality rate associated with established infection. Research indicates that:
- High-dose oral acyclovir is recommended for immediate prophylaxis when there is potential exposure to B virus infection 2
- The CDC recommends acyclovir 800 mg every 4 hours, 5 times daily for herpesvirus infections 1
- This dosing regimen provides the best chance of preventing viral replication before systemic infection can be established
Duration of Prophylaxis
- Prophylaxis should be continued for at least 14 days, with consideration for extending to 21 days in cases of high-risk exposure
- Research has shown that a 21-day course of high-dose acyclovir prevented death in animal models of B virus infection 2
Dosage Adjustments
Renal function must be assessed before initiating therapy, with dosage adjustments as follows:
| Creatinine Clearance (mL/min) | Dose Adjustment for 800 mg |
|---|---|
| >25 | 800 mg every 4 hours, 5 times a day |
| 10-25 | 800 mg every 8 hours |
| 0-10 | 800 mg every 12 hours |
Alternative Considerations
- If signs or symptoms of B virus infection develop despite prophylaxis, immediate transition to high-dose intravenous acyclovir is warranted
- Ganciclovir may be more effective than acyclovir against B virus and could be considered for treatment of established infection 2
- For immunocompromised patients, more aggressive prophylaxis and monitoring may be necessary 1
Important Clinical Considerations
- Prophylaxis should begin as soon as possible after exposure - ideally within hours
- The bite wound should be thoroughly cleansed and irrigated before starting antiviral therapy
- Cultures of the wound should be obtained before initiating treatment
- Monitor for signs of infection including vesicular lesions, neurological symptoms, or flu-like illness
- Laboratory confirmation of B virus infection is challenging and should not delay treatment
Potential Pitfalls
- Delaying prophylaxis significantly reduces effectiveness
- Using standard herpes simplex dosing (200-400 mg) is inadequate for B virus prophylaxis
- Failure to adjust dosing based on renal function may lead to toxicity
- Discontinuing prophylaxis too early may allow viral replication to resume
- Relying solely on topical antivirals is ineffective as they cannot reach the site of viral replication 1