Why is acyclovir given to patients with multiple myeloma?

Acyclovir Prophylaxis in Multiple Myeloma: Prevention of Varicella Zoster Virus Reactivation

Acyclovir is given to patients with multiple myeloma primarily to prevent varicella zoster virus (VZV) reactivation, which occurs at significantly higher rates in this population due to disease-related and treatment-related immunosuppression. 1

Risk Factors for VZV Reactivation in Multiple Myeloma

Multiple myeloma patients have a substantially elevated risk of VZV reactivation compared to the general population:

• 14.8-fold increased hazard ratio for VZV reactivation compared to the general population 1
• Specific treatments that significantly increase risk:
  • Proteasome inhibitors (e.g., bortezomib) 1
  • Anti-CD38 antibodies (e.g., daratumumab) 1
  • High-dose melphalan followed by autologous stem cell transplantation 1
  • High doses of glucocorticosteroids 1

Evidence Supporting Acyclovir Prophylaxis

The evidence strongly supports antiviral prophylaxis in multiple myeloma patients:

• In a retrospective study of 100 patients receiving bortezomib-based therapies with acyclovir prophylaxis (400 mg twice daily), none developed herpes zoster 2
• Another study of 33 patients showed that continuous daily 200 mg acyclovir completely prevented VZV reactivation (0% in prophylaxis group vs. 43% in non-prophylaxis group) 3
• Daily 500 mg valacyclovir was also shown to be effective, with only 1 breakthrough infection among 32 patients 4

Recommended Prophylactic Regimen

Based on current guidelines:

• All multiple myeloma patients should receive antiviral prophylaxis with acyclovir or valacyclovir 1
• Recommended dosing:
  • Acyclovir 400 mg twice daily or 800 mg twice daily 1, 2
  • Alternative: Valacyclovir 500 mg daily 4
• Duration of prophylaxis:
  • Continue throughout active myeloma treatment 1
  • For patients receiving proteasome inhibitors or anti-CD38 antibodies: maintain prophylaxis for the entire duration of therapy 1
  • For transplant patients: continue for at least 1 year after HSCT 1

Monitoring During Prophylaxis

• Routine monitoring while on acyclovir prophylaxis is not necessary 1
• Clinical vigilance for breakthrough infections should be maintained
• No specific laboratory monitoring is required for acyclovir at standard prophylactic doses

Special Considerations

• For patients with renal impairment: dose adjustment of acyclovir may be necessary
• For patients with history of prior VZV reactivation: prophylaxis is particularly important 4
• Compliance with prophylaxis is critical - one study noted VZV reactivation in a non-compliant patient despite prescribed prophylaxis 2

Complementary Approaches

The European Myeloma Network recommends:

• Consider recombinant VZV glycoprotein E vaccine for eligible patients (two doses 2-6 months apart) 1
• This vaccination strategy should be complemented by conventional prophylaxis with acyclovir or valacyclovir for optimal protection 1

Acyclovir prophylaxis is highly effective, well-tolerated, and should be considered standard of care for multiple myeloma patients, particularly those receiving immunosuppressive treatments that further increase VZV reactivation risk.