Background and Objective: Acyclovir is primarily cleared by the kidneys. Therefore, renal adjusted dosing is required for
patients with renal impairment to prevent drug toxicity. This study aimed to demonstrate the clinical manifestations and
treatment in case series of acyclovir toxicity.
Material and Method: We retrospectively reviewed 6 patients who were diagnosed acyclovir toxicity between January 1, 2005 and January 31, 2016 at Khon Kaen University’s Srinagarind Hospital.
Results: All 6 patients were diagnosed with herpes zoster infection and renal dysfunction. There were four end-stage renal
disease (ESRD) patients and two chronic kidney disease (CKD) patients. The neuropsychiatric symptoms occurred within
approximately 1-2 days after acyclovir was prescribed in ESRD patients and in 3 days in CKD patients. The symptoms were
lethargy, drowsiness, visual hallucinations, dysarthria, mutism, seizures, myoclonus, and weakness. Additionally, meningeal
irritation and cerebellar signs were observed upon physical examination. In severe cases, the patients suffered from respiratory failure. When acyclovir toxicity was suspected, acyclovir use was discontinued in all patients and emergency hemodialysis (HD) was performed in ESRD patients. All patients completely recovered consciousness after the second session.
Conclusion: Neuropsychiatric symptoms, meningeal irritation, and cerebellar signs may appear in cases of acyclovir toxicity. Clinical improvement after hemodialysis and discontinuation of acyclovir are key indicators leading to the diagnosis of acyclovir toxicity, and therapy should consist of two consecutive daily HD sessions.

Keywords: Acyclovir, Toxicity, Overdose