Shingles Risk with Mepolizumab
Yes, shingles (herpes zoster) is a recognized side effect of mepolizumab and other anti-IL-5 monoclonal antibodies, representing a potential class effect of this therapeutic category. 1
Evidence for Association
A case report documented disseminated herpes zoster following benralizumab (another anti-IL-5 monoclonal antibody) initiation, with the patient developing extensive vesicular lesions that progressed from localized lumbar dermatomes to widespread dissemination. 1 Clinical trials have specifically reported an association between mepolizumab and herpes zoster, suggesting this may be a class effect of anti-IL-5 monoclonal antibodies rather than an isolated drug-specific reaction. 1
Risk Stratification and Prevention
High-Risk Populations Requiring Heightened Vigilance
Patients on anti-IL-5 therapy face increased herpes zoster risk, particularly when combined with other immunosuppressive factors. 2 Immunocompromised patients on biologics demonstrate elevated zoster rates, with inflammatory bowel disease patients showing hazard ratios of 1.21 for ulcerative colitis and 1.61 for Crohn's disease. 2
Vaccination Strategy Before Initiating Mepolizumab
All patients aged 50 years or older should receive the recombinant zoster vaccine (Shingrix) before starting mepolizumab, as this non-live vaccine is safe and effective regardless of prior varicella history. 3, 4 The Advisory Committee on Immunization Practices recommends Shingrix for all adults aged 50+ regardless of medication use to prevent varicella-zoster virus reactivation. 3
For patients without documented varicella immunity, screen by history for chickenpox or shingles. 2 If history is uncertain or negative, test for varicella-zoster virus IgG. 2 Seronegative immunocompetent patients should complete a two-dose varicella vaccine course at least 3 weeks before starting mepolizumab. 2
Critical caveat: Live zoster vaccine (Zostavax) is contraindicated in immunocompromised patients and should never be used in this population. 2, 5 Only the recombinant vaccine (Shingrix) is appropriate for patients on biologic therapy. 3, 5
Clinical Presentation in Patients on Anti-IL-5 Therapy
Herpes zoster in immunocompromised patients presents more severely than in immunocompetent hosts. 6, 7 Expect more numerous skin lesions, often with hemorrhagic bases, prolonged disease duration (up to two weeks), and high risk for cutaneous dissemination and visceral involvement including viral pneumonia, encephalitis, and hepatitis. 8, 6
The case associated with benralizumab demonstrated progression from localized lumbar dermatomes to widespread dissemination, illustrating the potential severity in this population. 1
Treatment Algorithm for Herpes Zoster on Mepolizumab
Immediate Management (Within 72 Hours of Rash Onset)
For localized herpes zoster: Initiate oral valacyclovir 1000 mg three times daily or famciclovir 500 mg three times daily for 7-10 days, continuing until all lesions have completely scabbed. 4, 6, 7 Treatment must begin within 72 hours of rash onset for optimal efficacy in reducing acute pain, accelerating lesion healing, and preventing postherpetic neuralgia. 4, 7
For disseminated or severe disease: Switch immediately to intravenous acyclovir 10 mg/kg every 8 hours, continuing for minimum 7-10 days until clinical resolution with complete scabbing of all lesions. 4, 6 Intravenous therapy is mandatory for immunocompromised patients with disseminated infection, ophthalmic involvement, or visceral complications. 4, 6
Management of Immunosuppression
In severe cases of herpes zoster, consider temporarily discontinuing mepolizumab if possible until all vesicles have crusted over and fever has resolved. 2, 4 Immunomodulator therapy should not be reintroduced until this clinical endpoint is reached. 2
Monitoring Parameters
Monitor renal function closely during intravenous acyclovir therapy with dose adjustments for renal impairment. 4 If lesions fail to begin resolving within 7-10 days despite treatment, suspect acyclovir resistance and obtain viral culture with susceptibility testing. 4 For confirmed resistance, switch to foscarnet 40 mg IV every 8 hours until clinical resolution. 4, 6
Key Clinical Pitfalls to Avoid
Do not stop antiviral therapy at exactly 7 days if lesions are still forming or have not completely scabbed. 4 The clinical endpoint is complete crusting of all lesions, not an arbitrary calendar duration. 4 Immunocompromised patients may develop new lesions for 7-14 days and heal more slowly, requiring treatment extension well beyond the standard 7-10 day course. 4
Do not use topical antivirals, as they are substantially less effective than systemic therapy and are not recommended. 4, 6
Do not apply corticosteroid creams to active shingles lesions, as this can increase risk of severe disease and dissemination in immunocompromised patients. 4