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A case series using famciclovir in stem cell transplant recipients with valacyclovir hypersensitivity reactions

Background Herpes simplex virus and varicella zoster virus reactivation can occur in up to 32% and 40% of patients, respectively in the first year post-transplant without prophylaxis. Antiviral therapy consisting of acyclovir or valacyclovir is recommended for at least 1 year post stem cell transplant per evidence-based guidelines. Objective In the event of a contraindication or hypersensitivity reaction to either drug, an alternative is essential based on the proven efficacy in reducing clinically significant herpes simplex virus and varicella zoster virus reactivations. We report two cases of successful initiation of famciclovir in stem cell transplant recipients experiencing hypersensitivity to valacyclovir or acyclovir. Discussion In both cases, there were no hypersensitivity reactions or breakthrough viral infections after famciclovir initiation but this observation is limited by a small patient population. Conclusion Due to the limited data available, famciclovir appears to be a reasonable option in immunocompromised patients with a mild valacyclovir or acyclovir hypersensitivity reaction.