Valacyclovir-induced Neurotoxicity in a Patient with a Preserved Renal Function

Acyclovir-induced sinus bradycardia: a case report and literature review

In this report, we describe the case of a 51-year-old female who presented to our emergency department with varicella zoster infection. Her relevant medical history included rheumatoid arthritis which was treated with risankizumab. Intravenous acyclovir therapy was initiated due to concern for disseminated disease as she was experiencing T4 dermatomal involvement and new-onset scalp pain. On day 3 of antiviral therapy, the patient developed a sinus bradycardia of 35 beats/min. This persisted until 3 days after the discontinuation of acyclovir. This is the third reported case of sinus bradycardia potentially linked to acyclovir administration. Thus, clinicians should consider intravenous acyclovir as a possible cause of de novo sinus bradycardia.

Neurotoxicity associated with acyclovir and valacyclovir: A systematic review of cases

WHAT IS KNOWN AND OBJECTIVE

Acyclovir and valacyclovir are commonly used antivirals with good general tolerance. Despite their good safety profile, they can cause systemic adverse effects, such as neurotoxicity, which are less frequent and known. The objective of this review was to collect all the reported cases of neurotoxicity associated with acyclovir and valaciclovir published in the literature and characterize their clinical course and interventions.

METHODS

A systematic review of cases was carried out following the guidelines established by "Preferred Reporting Items for Systematic Reviews and Meta-Analyses" (PRISMA). The research was carried out using the PubMed-Medline and Embase databases, between July 1984 and March 2021.

RESULTS AND DISCUSSION

A total of 119 cases with neurotoxicity mainly related to acyclovir (n = 88; 73.9%), followed by valaciclovir (n = 35; 29.4%) were analysed. 49.6% (n = 59) were men with a mean age of 59.5 years ± 21.1 (0.5-88). In 83.3% of the cases, renal impairment was documented and 57.1% (n = 68) with end-stage renal disease. The administered dose was higher than the renal adjustment recommendations in 59.7% of the cases. The global mean of onset of symptoms was 3.1 days ± 4.3 (0.2-28) after the start of antivirals. The mean recovery time was 9.8 days ± 21.7 (0.2-180). 74.4% of the patients had a recovery of ≤7 days, 15.9% between 8 and 15 days and 9.8% > 15 days.

WHAT IS NEW AND CONCLUSION

The neurotoxicity induced by acyclovir and its derivative valacyclovir is a poorly known and rare adverse effect that can occur mainly in patients with advanced age and impaired renal function. The most characteristic symptoms are confusion, altered level of consciousness, hallucinations, agitation and dysarthria. The basis of treatment is the discontinuation of the antiviral, and in some cases, it may require additional clearance by dialysis.

When a Seemingly Harmless Prescription Turns into Toxicity

Valacyclovir neurotoxicity is commonly seen in the elderly and those with impaired renal function. Differential diagnosis can be challenging as a myriad of medical conditions, including herpes zoster virus associated encephalitis, may present in a similar fashion. We present a case of a 71-year-old male who presented with altered mental status in the setting of recent herpes zoster eruption. His condition was attributed to valacyclovir neurotoxicity, and initiation of appropriate supportive therapy was met with complete resolution of symptoms and normalization of cognitive function.