Based on the evidence, the current management of herpes zoster and its sequela post-herpetic neuralgia (PHN) relies upon the early onset of antiviral agents and analgesics, and depending on the severity of the pain those can be strong opioids.It is uncommon to monitor the renal function in patients with this treatment, even though there are reports of nephrotoxicity secondary to the antiviral use.We presented a case of a 49-year-old woman who was admitted for herpes zoster treatment, and developed renal insufficiency following a treatment with acyclovir.The main clinical manifestation was a change in the neurologic status, which was first interpreted as opioid toxicity.The patient was treated with hemodialysis obtaining full recovery.We consider this report relevant as it stresses the importance of monitoring the renal function in patients receiving this type of medication.