Duration of Acyclovir and Cotrimoxazole After Stopping Bortezomib
Continue acyclovir for at least 4 weeks after the last dose of bortezomib, and maintain trimethoprim-sulfamethoxazole (cotrimoxazole) prophylaxis throughout the entire duration of proteasome inhibitor therapy and for a period thereafter based on ongoing immunosuppression status.
Acyclovir Prophylaxis Duration
The FDA label for bortezomib explicitly recommends antiviral prophylaxis during treatment, noting that herpes zoster reactivation occurs in 6-11% of bortezomib-treated patients versus 3-4% in controls 1. The EHA-EMN guidelines specifically recommend acyclovir or valacyclovir for herpes zoster prophylaxis in patients receiving proteasome inhibitors 2.
The key timeframe is 4 weeks post-bortezomib discontinuation 3. This recommendation is supported by a retrospective study of 100 multiple myeloma patients where acyclovir 400 mg twice daily was initiated prior to bortezomib and discontinued 4 weeks following the last bortezomib dose, with complete prevention of herpes zoster reactivation 3.
Acyclovir Dosing Algorithm:
- Standard dose: 400 mg twice daily
- Start: Before or with first bortezomib dose
- Stop: 4 weeks after last bortezomib dose
- Monitor: One patient who was non-compliant developed VZV reactivation, emphasizing the importance of adherence 3
Trimethoprim-Sulfamethoxazole (Cotrimoxazole) Prophylaxis Duration
The EHA-EMN guidelines recommend sulfamethoxazole and trimethoprim for prevention of Pneumocystis jirovecii infection in multiple myeloma patients 2. However, the guidelines do not specify a fixed duration tied to bortezomib discontinuation alone.
Critical Considerations for TMP-SMX Duration:
Continue TMP-SMX prophylaxis based on:
- Ongoing immunosuppressive therapy (lenalidomide, dexamethasone, anti-CD38 antibodies)
- Lymphocyte count <1000/μL
- Overall disease burden and treatment response
The EHA-EMN guidelines specifically note prophylactic antibiotics for "the first 3 months of initiation of therapy, especially in patients receiving lenalidomide or pomalidomide" 2, but this applies to antibacterial prophylaxis. For PCP prophylaxis with TMP-SMX, duration should extend beyond bortezomib cessation if other immunosuppressive agents continue.
TMP-SMX Management Algorithm:
If bortezomib is stopped but other myeloma therapy continues:
- Continue TMP-SMX prophylaxis throughout maintenance therapy
- Monitor for adverse effects (hyperkalemia in 27-39% of patients, cytopenias in 35%) 4, 5
- Consider alternative prophylaxis (pentamidine, dapsone, atovaquone) only if TMP-SMX causes significant toxicity
If all myeloma therapy is stopped:
- Continue TMP-SMX for at least 3-6 months after complete cessation of immunosuppressive therapy
- Assess lymphocyte recovery and immune reconstitution
- Consider stopping when lymphocyte count >1000/μL and no active immunosuppression
Common Pitfalls to Avoid
Premature TMP-SMX discontinuation: 20% of transplant patients discontinue TMP-SMX early, with 62% never resuming it despite resolution of the adverse effect 5. If discontinued for hyperkalemia or cytopenias, attempt rechallenge once resolved—86% successfully tolerate resumption 5.
Assuming bortezomib cessation means immediate prophylaxis cessation: The immunosuppressive effects persist beyond the last dose, particularly with concurrent dexamethasone or immunomodulatory agents.
Not monitoring for TMP-SMX toxicity: Patients ≥50 years, lymphocyte count <1000/μL, and platelet count <180,000/μL are at higher risk for thrombocytopenia during TMP-SMX therapy 6. Monitor CBC regularly.
Forgetting that maintenance therapy continues immunosuppression: NCCN guidelines indicate primary therapy continues "until progression with de-escalation" 7, meaning prophylaxis needs often persist long after initial bortezomib-containing induction.
Summary Algorithm
Acyclovir: Stop 4 weeks after last bortezomib dose 3
TMP-SMX: