Does a patient with multiple myeloma on dexamethasone require prophylactic antiviral therapy with Zovirax (acyclovir)?

Antiviral Prophylaxis in Multiple Myeloma Patients on Dexamethasone

Yes, patients with multiple myeloma receiving dexamethasone should receive prophylactic antiviral therapy with acyclovir (Zovirax) to prevent herpes zoster reactivation. 1

Rationale for Antiviral Prophylaxis

Multiple myeloma patients are at increased risk of infections due to:

1. Disease-related immune dysfunction

   • Impaired B-cell function
   • Abnormalities in dendritic cells, T-cells, and NK-cells 1

2. Treatment-related factors

   • Corticosteroids (dexamethasone) cause immunosuppression
   • Proteasome inhibitors significantly increase herpes zoster risk

The NCCN guidelines specifically recommend prophylactic antiviral therapy for:

• All patients receiving proteasome inhibitor-based therapies
• All patients receiving antibody-based therapies 1

Recommended Prophylaxis Protocol

• Drug of choice: Acyclovir (Zovirax) or valacyclovir
• Dosage:
  • Acyclovir 400mg twice daily 2
  • Alternative: Valacyclovir 500mg daily 3
• Duration: Continue throughout dexamethasone treatment and for at least 4 weeks after discontinuation 2

Evidence Supporting Prophylaxis

Multiple studies have demonstrated the effectiveness of antiviral prophylaxis:

• A retrospective study of 100 MM patients on bortezomib-based therapies showed 0% incidence of herpes zoster with acyclovir prophylaxis 2
• Another study of 32 MM patients demonstrated that valacyclovir 500mg daily was effective in preventing VZV reactivation 3
• A 2023 study showed that patients without prophylaxis had 2.37 times higher risk of herpes zoster infection 4

Special Considerations

• Renal function: Dose adjustment may be needed for patients with renal impairment
• Compliance: Patient education regarding the importance of adherence is essential 5
• Duration: Prophylaxis should be maintained throughout the entire course of treatment with dexamethasone 1

Potential Pitfalls

1. Discontinuing too early: Antiviral prophylaxis should be continued for at least 4 weeks after stopping dexamethasone 2
2. Non-compliance: Patients who miss doses are at increased risk of herpes zoster 2
3. Inadequate monitoring: Regular assessment for signs of viral infection should continue despite prophylaxis

Algorithm for Decision-Making

1. For all MM patients on dexamethasone:

   • Initiate antiviral prophylaxis with acyclovir 400mg twice daily or valacyclovir 500mg daily
   • Start before or simultaneously with dexamethasone therapy

2. For patients with renal impairment:

   • Adjust dosage according to creatinine clearance
   • Consider nephrology consultation if severe impairment

3. For patients with history of herpes zoster:

   • Continue prophylaxis indefinitely while on immunosuppressive therapy
   • Consider higher dosing if breakthrough infection occurs

The evidence strongly supports that prophylactic antiviral therapy significantly reduces morbidity and mortality from herpes zoster infections in multiple myeloma patients receiving dexamethasone.