Acyclovir-induced bullous reaction in a patient with metastatic breast cancer

Acyclovir is a synthetic guanosine analog, which is a potent and highly selective inhibitor of the DNA polymerases of several herpes viruses. Acyclovir is known as a relatively safe drug with few significant adverse effects, of which nephrotoxicity seems to be the most dreaded one. On the other hand, inflammation and phlebitis at the injection site have been reported to be the most frequent side effects of intravenous acyclovir administration. Although exceptionally rare, there have been case reports of bullous eruption occurring after intravenous acyclovir therapy, a similar of which we have also observed. Here, we present a case of localized bullous eruption and phlebitis associated with intravenous acyclovir treatment in a patient with metastatic breast cancer. Our case distinctively demonstrated two consequential juxtaposing vesiculobullous lesions and phlebitis manifesting as erythema along the course of a vein after intravenous acyclovir injection. We emphasize this hardly known side effect and importance of early recognition and appropriate management of unpredictable side effects of widely used medications.