What is the dosing for Acyclovir (antiviral medication) for prophylaxis (prevention)?

From the Guidelines

Acyclovir dosing for preventative measures should be 400-800 mg 2-3 times daily for immunocompromised patients, as recommended by the most recent guidelines. The dosing regimen may vary depending on the specific indication and patient population. For example, patients undergoing allogeneic bone marrow transplantation may require acyclovir prophylaxis until day 30 after stem cell transplantation 1.

Key Considerations

• The duration of prophylaxis may be extended in patients with repeated episodes of HSV reactivation or those with graft-versus-host disease (GVHD) 1.
• Patients who are seronegative for HSV do not require acyclovir prophylaxis, regardless of the serostatus of the stem cell donor 1.
• Acyclovir prophylaxis should be discontinued when CMV prophylaxis or therapy with ganciclovir or foscarnet is initiated, as these agents are active against HSV in vitro 1.

Patient-Specific Factors

• Renal impairment may require dosing adjustments to prevent toxicity 1.
• Patients should be monitored regularly for potential side effects, such as headache, nausea, and dizziness, especially during long-term suppressive therapy.
• The choice of antiviral agent may depend on the specific clinical scenario, with valacyclovir and famciclovir being alternative options for HSV prophylaxis 1.

From the FDA Drug Label

Recurrent Genital Herpes: Double-blind, placebo-controlled studies in patients with frequent recurrences (6 or more episodes per year) have shown that orally administered acyclovir given daily for 4 months to 10 years prevented or reduced the frequency and/or severity of recurrences in greater than 95% of patients

• The recommended dosing for preventative use of acyclovir is not explicitly stated in the label for all conditions, but for Recurrent Genital Herpes, the label mentions that acyclovir given daily for 4 months to 10 years prevented or reduced the frequency and/or severity of recurrences.
• For Recurrent Genital Herpes, a dose of 400 mg twice daily for 3 years was used in one study, with 45%, 52%, and 63% of patients remaining free of recurrences in the first, second, and third years, respectively 2.

From the Research

Acyclovir Dosing for Preventative Measures

• The standard dose of acyclovir for preventative measures is 1000 mg/day, as widely used in Japan for hematopoietic stem cell transplant (HSCT) patients 3.
• However, a lower dose of 200 mg/day has been shown to be effective in preventing herpes simplex virus (HSV) disease in the early phase after HSCT 3.
• Acyclovir is still the standard therapy for severe HSV and varicella virus infections, with a mortality rate of about 25% for herpes encephalitis 4.
• Long-term administration of acyclovir can lead to the development of drug resistance, particularly in immunocompromised patients 5.
• Acyclovir prophylaxis is recommended for organ transplant recipients and patients with hematologic malignancies undergoing induction chemotherapy who are seropositive for HSV 6.
• A single "stat" dose of 800 mg of acyclovir has been shown to be effective in preventing lesions from appearing in individuals with recurrent herpes simplex attacks 7.

Dosage Considerations

• The dosage of acyclovir may need to be adjusted based on the individual's immune status and the severity of the infection 4, 5.
• Immunocompromised patients may require higher doses or more frequent administration of acyclovir to prevent HSV disease 6.
• The development of resistance to acyclovir is a concern, particularly in immunocompromised patients, and alternative treatments such as foscarnet may be necessary 4, 5.