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

New Insights Into the Therapeutic Management of Varicella Zoster Virus Meningitis: A Series of 123 Polymerase Chain Reaction-Confirmed Cases

Background

Varicella zoster virus (VZV) can reactivate and cause meningitis, but few studies have distinguished it from meningoencephalitis regarding treatment recommendations.The objective of this study was to assess the outcomes of a large series of patients with VZV meningitis according to their therapeutic management.

Methods

We conducted a bicentric retrospective cohort study, in Paris, France, including all adult patients with a cerebrospinal fluid sample positive for VZV by polymerase chain reaction between April 2014 and June 2022. We distinguished meningitis from encephalitis according to the International Encephalitis Consortium criteria. Unfavorable outcome was defined as mortality or functional sequelae defined by a loss of 2 points on the modified Rankin Scale.

Results

We included 123 patients with meningitis. Among them, 14% received no antivirals, while 20% were treated with oral valacyclovir alone, 41% with a short course of intravenous (IV) acyclovir before switch to valacyclovir, and 25% with a long course of IV acyclovir. Outcomes were favorable regardless of antiviral regimen. In multivariate analysis, only age, underlying immunosuppression, and cranial radiculitis appear to be predictive factors for longer IV therapy, based on the Akaike information criterion.

Conclusions

In this study, patients with VZV meningitis had a good outcome, with no evidence of any impact of the treatment strategy. However, further studies are needed to support the possibility of milder treatment in immunocompetent patients, avoiding cost and side effects of IV acyclovir.

Characteristics, management and outcome of Herpes Simplex and Varicella-Zoster virus encephalitis: a multicentre prospective cohort study

OBJECTIVE

To characterize differences between Herpes Simplex virus encephalitis and Varicella-Zoster virus encephalitis (HSVE and VZVE) and other aetiologies of infectious encephalitis (IE), and to investigate the impact of time-to-aciclovir (ACV) start, ACV dose and duration on outcome.

METHODS

We compared 132 HSVE, 65 VZVE and 297 other IE enrolled in a prospective cohort (ENCEIF). We estimated associations between time-to-ACV start, dose or duration and outcome through adjusted odds ratio (aOR) using logistic regression analysis.

RESULTS

Prevalence of immunodepression differed among aetiologies: 15/65 (23%) for VZVE, 13/132 (10%) for HSVE and 30/297 (10%) for other IE (p <0.05), as was presence of seizure at admission: 27/132 (20%) for HSVE, 4/65 (6%) for VZVE and 43/297 (14%) for other IE (p <0.05). Poor outcome at hospital discharge (Glasgow outcome scale ≤3) differed among the three groups: 40/127 (31%) for HSVE, 12/65 (18%) for VZVE and 38/290 (13%) for other IE (p <0.05). Time-to-ACV start was associated with outcome in HSVE (aOR 3.61 [1.25-10.40]), but not in VZVE (aOR 0.84 [0.18-3.85]). Increased ACV dose was not associated with outcome among HSVE (aOR 1.25 [0.44-3.64]) nor VZVE (aOR 1.16 [0.24-5.73]).

DISCUSSION

HSVE and VZVE are distinct in clinical presentation, outcome and prognostic factors. The impact of early ACV initiation was more apparent for HSVE than for VZVE; however, this could be because of VZVE's smaller sample size and lower outcome rate leading to low statistical power or because of potential distinct IE pathophysiology.

Simultaneous analysis of acyclovir and its metabolite using hydrophilic interaction liquid chromatography-tandem mass spectrometry

The antiviral drug acyclovir (ACV) may induce drug-induced neuropsychiatric symptoms as side effects. The detailed pathogenic mechanism remains unclear; however, it is hypothesized that 9-carboxymethoxymethylguanine (CMMG), a metabolite of ACV, is the causative compound. Therefore, the blood concentrations of ACV and CMMG should be analyzed in ACV toxicity studies. However, it is rare to find methods that can sufficiently separate the ACV and CMMG peaks during simultaneous analysis of both compounds. Therefore, we intended to develop a liquid chromatography-tandem mass spectrometry method with improved peak separation of analytes. Samples were deproteinized using methanol/acetonitrile solution (6:4, v/v). Analytes were separated on an InertSustain® Amide column (3 μm, 2.1 mm × 150 mm). The mobile phase consisted of acetonitrile/10 mM ammonium formate (5:95, v/v) (A) and acetonitrile/10 mM ammonium formate (95:5, v/v, pH 5.0) (B) and samples were eluted in the gradient mode. The separation of analytes was satisfactory and the peak shapes were good. Linear regression models weighted 1/x2 were obtained in the range of 0.25-10 μg/mL. The range of quality control (QC) bias was between 3.6% and 19.8%, and the within-run and between-run precisions of QC were within 13.5%. Recovery ranged from 83.6% to 103.7%, but ion suppression was observed. Samples from a patient with ACV encephalopathy were analyzed using this method. The resulting blood ACV and CMMG concentrations were 8.2 and 8.5 μg/mL, respectively. This method, with sufficient separation of ACV and CMMG, proved useful for use in ACV toxicity studies.

Acyclovir dosing in herpes encephalitis: A scoping review

BACKGROUND

Herpes encephalitis, a rare yet potentially fatal viral infection, is treated exclusively with acyclovir, the sole antiviral medication used for this condition. Acyclovir recommended dose is 10 mg/kg/dose intravenous every 8 hours; however, it is unclear what body weight should be utilized in obese patients. Using the ideal body weight may result in subtherapeutic ineffective concentrations, while utilizing the actual body weight might result in acyclovir induced adverse effects, either nephrotoxicity or neurotoxicity or both.

OBJECTIVE

The objective of this scoping review is to explore existing evidence regarding acyclovir dosing for obese patients afflicted with herpes encephalitis.

METHODS

MEDLINE, EMBASE, Scopus, Web of Science, and CINAHL databases were searched on 26 May 2023, with no language restrictions. Two independent reviewers utilized the Covidence software to carry out the screening and selection of the articles. A total of 22 articles were included in the current review.

RESULTS

The prevalence of acyclovir-associated nephrotoxicity ranged from 13% to 21%, while the prevalence of neurotoxicity was not clearly defined. However, there is lack of evidence regarding what may arise from subtherapeutic concentrations. An approach has been suggested to help clinicians to give the most appropriate acyclovir dose to herpes encephalitis patients. Patients with normal kidney function could receive the normal doses based on actual weight if normal weight and based on adjusted body weight if obese. On the other hand, if the patients are experiencing augmented renal clearance, they could receive up to the maximum recommended doses.

CONCLUSION

Overall, there is a lack of consistency on which body weight to use to calculate acyclovir dose in obese patients. So it is recommended that further studies compare the concentration of intravenous acyclovir between obese and nonobese patients and relating the resultant concentration with patient outcomes.

HMBA ameliorates obesity by MYH9- and ACTG1-dependent regulation of hypothalamic neuropeptides

The global epidemic of obesity remains a daunting problem. Here, we report hexamethylene bisacetamide (HMBA) as a potent anti-obesity compound. Peripheral and central administration of HMBA to diet-induced obese mice regulated the expression of hypothalamic neuropeptides critical for energy balance, leading to beneficial metabolic effects such as anorexia and weight loss. We found that HMBA bound to MYH9 and ACTG1, which were required for the anti-obesity effects of HMBA in both NPY-expressing and POMC-expressing neurons. The binding of HMBA to MYH9 and ACTG1 elevated the expression of HEXIM1 and enhanced its interaction with MDM2, resulting in the dissociation of the HEXIM1-p53 complex in hypothalamic cells. Subsequently, the free HEXIM1 and p53 translocated to the nucleus, where they downregulated the transcription of orexigenic NPY, but p53 and acetylated histone 3 upregulated that of anorexigenic POMC. Our study points to a previously unappreciated efficacy of HMBA and reveals its mechanism of action in metabolic regulation, which may propose HMBA as a potential therapeutic strategy for obesity.

Drugs with a negative impact on cognitive functions (Part 2): drug classes to consider while prescribing in CKD patients

There is growing evidence that chronic kidney disease (CKD) is an independent risk factor for cognitive impairment, especially due to vascular damage, blood-brain barrier disruption and uremic toxins. Given the presence of multiple comorbidities, the medication regimen of CKD patients often becomes very complex. Several medications such as psychotropic agents, drugs with anticholinergic properties, GABAergic drugs, opioids, corticosteroids, antibiotics and others have been linked to negative effects on cognition. These drugs are frequently included in the treatment regimen of CKD patients. The first review of this series described how CKD could represent a risk factor for adverse drug reactions affecting the central nervous system. This second review will describe some of the most common medications associated with cognitive impairment (in the general population and in CKD) and describe their effects.

A decreasing plasma concentration of a toxicologically active metabolite 9-carboxymethoxymethylguanine after dialysis - A potential new clinical biomarker for improving encephalopathy in patients treated with acyclovir

Although acyclovir is a key drug for the treatment of herpes infections, a consciousness disorder known as "acyclovir encephalopathy" is among its side effects. We encountered a patient with encephalopathy and measured the plasma and cerebrospinal fluid concentrations of acyclovir and its toxicologically active metabolite 9-carboxymethoxymethylguanine (CMMG). Before dialysis, cerebrospinal fluid concentrations of acyclovir and CMMG in this patient with a consciousness disorder were approximately 10% and 1%, respectively, of their plasma concentrations. After 3 days of dialysis, plasma CMMG levels decreased to detectable but below quantitative levels (<0.1 μg/mL), resulting in normal consciousness. These results suggest that decreasing plasma CMMG concentration could be one of clinical biomarkers for improving consciousness in patients with encephalopathy associated with acyclovir.

In vivo CRISPR gene editing in patients with herpetic stromal keratitis

In vivo CRISPR gene therapy holds large clinical potential, but the safety and efficacy remain largely unknown. Here, we injected a single dose of herpes simplex virus 1 (HSV-1)-targeting CRISPR formulation in the cornea of three patients with severe refractory herpetic stromal keratitis (HSK) during corneal transplantation. Our study is an investigator-initiated, open-label, single-arm, non-randomized interventional trial at a single center (NCT04560790). We found neither detectable CRISPR-induced off-target cleavages by GUIDE-seq nor systemic adverse events for 18 months on average in all three patients. The HSV-1 remained undetectable during the study. Our preliminary clinical results suggest that in vivo gene editing targeting the HSV-1 genome holds acceptable safety as a potential therapy for HSK.

Polymer-Based Nanoparticles as Drug Delivery Systems for Purines of Established Importance in Medicine

Many purine derivatives are active pharmaceutical ingredients of significant importance in the therapy of autoimmune diseases, cancers, and viral infections. In many cases, their medical use is limited due to unfavorable physicochemical and pharmacokinetic properties. These problems can be overcome by the preparation of the prodrugs of purines or by combining these compounds with nanoparticles. Herein, we aim to review the scientific progress and perspectives for polymer-based nanoparticles as drug delivery systems for purines. Polymeric nanoparticles turned out to have the potential to augment antiviral and antiproliferative effects of purine derivatives by specific binding to receptors (ASGR1-liver, macrophage mannose receptor), increase in drug retention (in eye, intestines, and vagina), and permeation (intranasal to brain delivery, PEPT1 transport of acyclovir). The most significant achievements of polymer-based nanoparticles as drug delivery systems for purines were found for tenofovir disoproxil in protection against HIV, for acyclovir against HSV, for 6-mercaptopurine in prolongation of mice ALL model life, as well as for 6-thioguanine for increased efficacy of adoptively transferred T cells. Moreover, nanocarriers were able to diminish the toxic effects of acyclovir, didanosine, cladribine, tenofovir, 6-mercaptopurine, and 6-thioguanine.

A Case Report of Valacyclovir-Associated Neurotoxicity in End-Stage Renal Disease: A Rare but Preventable Side Effect

Neurotoxicity can develop as a side effect of valacyclovir in patients with renal disease, especially without a renally adjusted dose. We present a 56-year-old female with end-stage renal disease (ESRD) on hemodialysis (HD) who presented to the emergency room (ER) with agitation and confusion and was found to have valacyclovir-associated neurotoxicity (VAN). Five days prior, she had been prescribed the standard treatment of 500 mg valacyclovir twice daily for three days for herpes simplex virus-1 (HSV-1); however, her creatinine clearance was low enough to require a renally adjusted dose. Her condition was worsened from missing a dialysis session due to acute confusion. She was treated with three days of hemodialysis sessions. Improvement in mentation and agitation was observed after the second day of hemodialysis, and a complete resolution of symptoms and return to cognitive baseline occurred two days later. There are reports of daily hemodialysis shortening the neurotoxicity period and resulting in a faster return to normal mentation. This case is important as the dose of valacyclovir must be adjusted in those with kidney disease.

Aciclovir-induced neurotoxicity

Aciclovir-induced neurotoxicity results from the accumulation of aciclovir and its metabolite 9-carboxymethoxymethylguanine (CMMG). It occurs predominantly in older patients with impaired renal function and is characterised by a combination of confusion and psychiatric changes. Seizures, myoclonus and dysarthria may also occur. Critically, peritoneal dialysis has little effect on reversing the toxic effects of aciclovir. We describe a woman in her 70s with renal failure who developed confusion and seizures after receiving aciclovir. She was ultimately diagnosed with aciclovir-induced neurotoxicity, confirmed by an elevated serum CMMG concentration. This condition is likely to be underdiagnosed and the neurologist's primary challenge is differentiating aciclovir-induced neurotoxicity from viral encephalitis.

Antiviral drugs

In this chapter, we have reviewed side effects reported with the use of antivirals for the treatment of the following infections: coronavirus disease 2019 (COVID-19), cytomegalovirus (CMV), hepatitis B virus (HBV), hepatitis C Virus (HCV), herpes simplex viruses 1 and 2 (HSV-1, -2), human immunodeficiency virus (HIV), and influenza virus. The search engines PUBMED, EMBASE and International Pharmaceutical Abstracts (IPA) were utilized to identify literature published between January 1, 2021 to December 31, 2021.

Rapid determination of acyclovir, its main metabolite 9-carboxymethoxymethylguanine, ganciclovir and penciclovir in human serum by LC-MS/MS

A novel MS‐based analytical method for simultaneous analysis of the antiviral drugs acyclovir, its metabolite 9‐carboxymethoxymethylguanine, ganciclovir, and penciclovir in human serum is described. These antiviral drugs are active against herpes virus infections. Acyclovir and penciclovir are regarded as safe and effective medicines with mild side effects such as headache and gastrointestinal discomfort, and ganciclovir is regarded as more toxic and is known to cause, for example, bone marrow suppression. Acyclovir’s main metabolite 9‐carboxymethoxymethylguanine is a presumptive neurotoxin and should be monitored in patients with impaired renal function or in cases with neurotoxic symptoms. A sample was prepared using protein precipitation with 1% formic acid in methanol containing isotopically labeled internal standard. Chromatographic separation on a biphenyl column and mass spectrometric detection were performed in multiple reaction monitoring (MRM) mode on a Xevo TQ‐S micro with ESI in positive ion mode, within 3 min. Inter‐day assay accuracies for the quality controls varied between 95 and 104% and intra‐day assay between 93 and 105%. Inter‐day and intra‐day assay imprecision for the quality controls ranged between 1.4 and 4.2% and 1.7 and 6.5% respectively. The lower limit of quantification for all four substances was 0.156 μmol/L. It is an accurate and reproducible method for therapeutic drug monitoring.