# A Dose Too Far: Valacyclovir’s Surprising Side Effect

## TL;DR

This paper reports a case of valacyclovir causing psychosis in a patient with kidney disease, highlighting the need to consider kidney function when prescribing the drug.

## Contribution

The novelty lies in presenting a rare case linking valacyclovir-induced psychosis to pre-existing renal failure.

## Key findings

- Valacyclovir-induced psychosis occurred in a patient with renal failure.
- Psychiatric complications can arise even in patients with normal renal function.
- Renal impairment increases the risk of drug accumulation and neurological complications.

## Abstract

Valacyclovir, a prodrug of acyclovir, is a widely prescribed antiviral medication known for its efficacy in treating herpes infections. Although generally considered safe, rare cases of psychiatric adverse effects, including psychosis, have been reported. The precise mechanism underlying valacyclovir-induced psychosis remains unclear, but proposed explanations include potential neurotoxicity and alterations in neurotransmitter activity. Importantly, such adverse effects have been documented even in patients with normal renal function. Given that valacyclovir's pharmacokinetics are significantly altered in individuals with renal impairment - characterized by reduced clearance and prolonged half-life - the risk of drug accumulation and subsequent neurological complications is heightened in this population. Here, we present a unique case of valacyclovir-induced psychosis in a patient with pre-existing renal failure, emphasizing the importance of considering renal function when prescribing and monitoring this medication to mitigate the risk of psychiatric complications.