Aciclovir and valaciclovir neurotoxicity in patients with renal failure

Acyclovir Neurotoxicity in a Peritoneal Dialysis Patient: Report of a Case and Review of the Pharmacokinetics of Acyclovir

BACKGROUND The elderly population in the United States and the world is rapidly increasing. With aging, immunity and kidney function decrease, thus predisposing people to viral illnesses for which there is no effective prophylaxis. Herpes zoster afflicts the elderly and other immunocompromised patients, like those with end-stage renal disease, transplant recipients, and cancer patients, causing significant morbidity and sometimes mortality. Treating herpes zoster becomes problematic when the regular pharmacokinetics of the antiviral drugs are disturbed. CASE REPORT An 83-year-old African American man with end-stage kidney disease (ESRD) and on chronic peritoneal dialysis (PD) developed herpes zoster, for which he received the manufacturer-recommended intravenous dose of acyclovir. Shortly after taking the medication, he developed confusion, disorientation, and visual hallucinations. He was switched from PD to hemodialysis (HD), with successful recovery. Examination of the cerebrospinal fluid for meningitis and imaging studies of the head were negative. Serum levels of acyclovir were elevated. CONCLUSIONS Even when the acyclovir dose is properly adjusted for kidney function based on the current manufacturer's recommendations, it can cause neurotoxicity. Here, we discuss the pharmacokinetics of acyclovir and make some recommendations with regard to dose adjustment in patients with ESRD.

Resolution of acyclovir-associated neurotoxicity with the aid of improved clearance estimates using a Bayesian approach: A case report and review of the literature

WHAT IS KNOWN AND OBJECTIVE

Neurotoxicity is a side effect of acyclovir. We report the first case, to our knowledge, whereby Bayesian-informed clearance estimates supported a therapeutic intervention for acyclovir-associated neurotoxicity.

CASE SUMMARY

A 62-year-old male with the diagnosis of disseminated zoster was being treated with intravenous (IV) acyclovir when he developed symptoms of acute neurotoxicity. Acyclovir had been dose-adjusted for renal dysfunction according to traditional creatinine clearance estimates; however, as the patient was also on vancomycin, Bayesian estimates of vancomycin clearances were performed, which revealed a 2-fold lower creatinine clearance. In response to the Bayesian estimates, acyclovir was discontinued, and improvements in mentation were noted within 24 hours.

WHAT IS NEW AND CONCLUSION

Alternate approaches to estimate renal function beyond Cockcroft-Gault, such as a Bayesian approach used in our patient, should be considered when population estimates are likely to be inaccurate and potentially dangerous to the patient.

Neuropsychiatric complications of chronic kidney disease

Evidence is emerging that cognitive impairment, delirium and depression are very common in patients with renal disease. All of these conditions are associated with prolonged hospitalization and an increased risk of mortality. A good understanding of these conditions is key to their prevention, early intervention and management. This Review summarizes the clinical features of various forms of cognitive dysfunction that occur in individuals with renal disease and describes the evidence for the high burden of disease in such patients.

Pharmacokinetics of acyclovir and its metabolites in cerebrospinal fluid and systemic circulation after administration of high-dose valacyclovir in subjects with normal and impaired renal function

Valacyclovir, the L-valyl ester prodrug of acyclovir (ACV), is widely prescribed to treat infections caused by varicella-zoster virus or herpes simplex virus. Rarely, treatment is complicated by reversible neuropsychiatric symptoms. By mechanisms not fully understood, this occurs more frequently in the setting of renal impairment. We characterized the steady-state pharmacokinetics of ACV and its metabolites 9-[(carboxymethoxy)methyl]guanine (CMMG) and 8-hydroxy-acyclovir (8-OH-ACV) in cerebrospinal fluid (CSF) and the systemic circulation. We administered multiple doses of high-dose valacyclovir to 6 subjects with normal renal function and 3 subjects with chronic renal impairment (creatinine clearance [CrCl], approximately 15 to 30 ml/min). Dosages were 2,000 mg every 6 h and 1,500 mg every 12 h, respectively. Indwelling intrathecal catheters allowed serial CSF sampling throughout the dosing interval. The average steady-state concentrations of acyclovir, CMMG, and 8-OH-ACV were greater in both the systemic circulation and the CSF among subjects with impaired renal function than among subjects with normal renal function. However, the CSF penetration of each analyte, reflected by the CSF-to-plasma area under the concentration-time curve over the 6- or 12-h dosing interval (AUC(tau)) ratio, did not differ based on renal function. Renal impairment does not alter the propensity for ACV or its metabolites to distribute to the CSF, but the higher concentrations in the systemic circulation, as a result of reduced elimination, are associated with proportionally higher concentrations in CSF.