High serum concentrations of the acyclovir main metabolite 9-carboxymethoxymethylguanine in renal failure patients with acyclovir-related neuropsychiatric side effects: an observational study

Acyclovir-induced nephrotoxicity: the role of the acyclovir aldehyde metabolite

For decades, acyclovir-induced nephrotoxicity was believed to be secondary to crystalluria. Clinical evidence of nephrotoxicity in the absence of crystalluria suggests that acyclovir induces direct insult to renal tubular cells. We postulated that acyclovir is metabolized by the alcohol dehydrogenase (ADH) enzyme to acyclovir aldehyde, which is metabolized by the aldehyde dehydrognase 2 (ALDH2) enzyme to 9-carboxymethoxymethylguanine (CMMG). We hypothesized that acyclovir aldehyde plays a role in acyclovir-induced nephrotoxicity. Human renal proximal tubular (HK-2) cells were used as our in vitro model. Western blot and enzymes activities assays were performed to determine whether the HK-2 cells express ADH and ALDH2 isozymes, respectively. Cytotoxicity (measured as a function of cell viability) assays were conducted to determine (1) whether the acyclovir aldehyde plays a role in acyclovir-induced nephrotoxicity and (2) whether CMMG induces cell death. A colorimetric assay was performed to determine whether acyclovir was metabolized to an aldehyde in vitro. Our results illustrated that (1) HK-2 cells express ADH and ALDH2 isozymes, (2) 4-methylpyrazole rendered significant protection against cell death, (3) CMMG does not induce cell death, and (4) acyclovir was metabolized to an aldehyde in tubular cells. These data indicate that acyclovir aldehyde is produced in HK-2 cells and that inhibition of its production by 4-methylpyrazole offers significant protection from cell death in vitro, suggesting that acyclovir aldehyde may cause the direct renal tubular insult associated with acyclovir.

Neurotoxicity Associated with Standard Doses of Valacyclovir in Renal Insufficiency

Chronic kidney disease is a growing problem in the United States that increases the risk of medication-related complications. The antiviral medication valacyclovir hydrochloride is indicated for the treatment and/or suppression of herpes labialis, genital herpes, and herpes zoster and requires dosage adjustment for renal impairment. Valacyclovir is generally well tolerated, but serious adverse drug reactions have been reported including neurotoxicity and acute renal failure, especially in the elderly and in those with chronic kidney disease. We present 2 cases of neurotoxicity suspected to be secondary to non-renally dose-adjusted valacyclovir therapy. The first is a female hemodialysis patient who developed neuropsychiatric symptoms within 24 hours of initiating valacyclovir therapy; the second is an elderly gentleman with stage 4 chronic kidney disease and symptoms after 2 days of therapy. Both were prescribed valacyclovir 1 g orally 3 times daily despite renal impairment. Use of the Naranjo adverse drug reaction probability scale suggests probable associations between neuropsychiatric symptoms displayed by the patients and valacyclovir (score of 5 in case 1; score of 7 in case 2). These cases highlight the importance of considering renal status when dosing medications that undergo significant renal elimination.

Acyclovir nephrotoxicity: a case report highlighting the importance of prevention, detection, and treatment of acyclovir-induced nephropathy

Acute kidney injury is an unfortunate complication of acyclovir therapy secondary to crystal-induced nephropathy. It is characterized by a decrease in renal function that develops within 24–48 hours of acyclovir administration indicated by a rapid rise in the serum creatinine. Failure to quickly realize this as an etiology of acute kidney injury can lead to excessive morbidity to the patient. The case described in this vignette is an example of the clinical manifestation of acyclovir crystal obstructive nephrotoxicity. We will briefly discuss the pathophysiology, diagnosis, prevention, and management of patients that present with acyclovir nephrotoxicity.

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.

Valacyclovir neurotoxicity: clinical experience and review of the literature

Valacyclovir (VACV) is used increasingly to treat herpes zoster, although neuropsychiatric symptoms [VACV neurotoxicity (VAN) or acyclovir neurotoxicity], may accompany use of this drug. To promote awareness of this rare condition, we describe here two clinical cases of VAN we previously reported and review 20 cases from the literature. In all cases, chronic or acute renal failure preceded VAN. The symptoms of VAN varied, but disturbances of consciousness and hallucination occurred most commonly. When acute renal failure was due to the drug, recovery from both the disturbance of consciousness and renal failure followed within several days after discontinuation of VACV. Early recognition and diagnosis will ensure effective treatment of VAN.

Influence of ALDH2 genetic polymorphisms on aciclovir pharmacokinetics following oral administration of valaciclovir in Japanese end-stage renal disease patients

This study was performed to investigate the pharmacokinetics of valaciclovir (VACV), aciclovir (ACV) and 9-(carboxymethoxy)methylguanine (CMMG) in Japanese chronic hemodialysis patients following a single oral administration of 1000 mg VACV and the influence of genetic polymorphisms of aldehyde dehydrogenase-2 (ALDH2) on their pharmacokinetics. A total of eighteen individuals genotyped as ALDH2*1/*1, ALDH2*1/*2 or ALDH2*2/*2 were enrolled in this study. Blood samples were obtained pre-dose and up to 48 hour post-dose. ACV t(1/2) was significantly affected by ALDH2 genotype and prolonged in the order of ALDH2*1/*1 (18.1 hr)<ALDH2*1/*2 (21.9 hr)<ALDH2*2/*2 (26.7 hr). ACV AUC from zero to infinity (AUC(0-infinity)) increased with prolonged ACV t(1/2). ACV C(max) was similar across the three ALDH2 genotype groups. There was no apparent relationship between ALDH2 genotype and VACV or CMMG pharmacokinetics. This is the first study to show an association between ALDH2 genetic polymorphisms and ACV elimination rate (t(1/2)) in Japanese end-stage renal disease patients.

Death delusion

Anders Helldén and colleagues report two cases of Cotard’s syndrome that occurred as an adverse drug reaction to aciclovir and its prodrug valaciclovir

Acyclovir-induced neuropsychosis successfully recovered after immediate hemodialysis in an end-stage renal disease patient

A 70-year-old man developed herpes zoster over the right L5-S2 region for 3 days and was admitted for acyclovir therapy. He had a medical history of rectal cancer status post-colostomy and end-stage renal disease undergoing thrice weekly hemodialysis. Without a prior loading dose, acyclovir 500 mg (7.7 mg/kg) daily was given intravenously in two divided doses. On the third dosage, the patient became confused and agitated and developed insomnia. Within the following 24 h, delirium, visual and auditory hallucinations, disorientation to place and time, as well as impaired recent memory occurred. At the same time, a transient low grade fever (38 degrees C) was noted but resolved spontaneously after ice pillow (Fig. 1). The etiology was vigorously explored. He had no history of any neurological or psychiatric disorders. Drug history was reviewed, but no other medications besides acyclovir were currently being used. Physical examination revealed neither meningeal signs nor focal neurological deficits. Serum blood urea nitrogen, glucose, and electrolytes were within normal limits except for an elevated creatinine level at 6.2 and 5.7 mg/dl (before and after neuropsychotic symptoms, respectively). Complete blood count with differentiation was also unremarkable. Cerebrospinal fluid examination was not possible as the patient's family refused the lumbar puncture. Moreover, an electroencephalograph study and head computed tomography scan disclosed no abnormalities. Acyclovir-induced neurotoxicity was suspected. Therefore, acyclovir was discontinued. Subsequently, serum acyclovir and CMMG were checked by enzyme-linked immunosorbent assay. Serum acyclovir level was 1.6 mg/l (normal therapeutic level, 0.12-10.8 mg/l) and CMMG level was 5 mg/l. Emergent hemodialysis (4-h/session) was given; the neuropsychotic symptoms, including agitation, delirium, and visual and auditory hallucinations, greatly abated after the second session. The patient fully recovered after three consecutive days of hemodialysis; the serum was rechecked and revealed that the acyclovir level was below 0.5 mg/l and the CMMG level was undetectable. At the same time, his herpetic skin lesions resolved well.

Development, evaluation and application of an isocratic high-performance liquid chromatography (HPLC) assay for the simultaneous determination of aciclovir and its metabolite 9-carboxymethoxymethylguanine in human serum and cerebrospinal fluid

9-Carboxymethoxymethylguanine (CMMG), the main metabolite of aciclovir (ACV), is a putative neurotoxin. Measurement of CMMG in body fluids may aid patient management. We describe the development, validation and application of a high-performance liquid chromatography (HPLC) method for the simultaneous determination of ACV and CMMG in human serum and cerebrospinal fluid (CSF). Recovery was between 94% and 100% at all concentrations both from serum (range 0-20 mg/L) and CSF (0-5 mg/L). The intra-assay precision (coefficient of variation (CV)) was <2% and the inter-assay precision (CV) was <5%. The limits of detection and quantification were 0.1 and 0.25 mg/L, respectively, in both body fluids. Significant interference from endogenous material or from drugs in clinical samples was not seen. CMMG was detected in most of the 55 clinical samples containing ACV, but little correlation was found between the levels of the drug and its metabolite.

Neurological toxicity of acyclovir: report of a case in a six-month-old liver transplant recipient

Acyclovir-induced neurotoxicity is a rare adverse effect, found especially in adults with pre-existing renal failure. We report a case of neurotoxicity of acyclovir in a six-month-old liver transplant recipient. Case report and review of literature are discussed.

The aciclovir metabolite CMMG is detectable in the CSF of subjects with neuropsychiatric symptoms during aciclovir and valaciclovir treatment

OBJECTIVES

Neuropsychiatric symptoms related to aciclovir or valaciclovir treatment have been a problem since aciclovir was introduced in the early 1980s. We have previously found that subjects with aciclovir-related neuropsychiatric symptoms have increased serum concentrations of aciclovir's main metabolite, 9-carboxymethoxymethylguanine (CMMG). The aim of this study was to investigate whether CMMG was present in the CSF of aciclovir- or valaciclovir-treated subjects with or without neuropsychiatric side effects that appeared during therapy.

METHODS

We investigated retrospectively CSF collected from 21 aciclovir- or valaciclovir-treated subjects. Of these, 9 were subjects with neuropsychiatric signs and symptoms and 12 were asymptomatic subjects, including 10 subjects from a valaciclovir multiple sclerosis trial and 2 subjects with recurrent herpes encephalitis.

RESULTS

CMMG could only be detected in the CSF of subjects with neuropsychiatric symptoms and signs (median CMMG concentration 1.0 micromol/L, range 0.6-7.0). The concentration of CMMG was below the limit of quantification (<0.5 micromol/L) in asymptomatic subjects (P < 0.001). All patients with neuropsychiatric signs and symptoms, except one, had acute renal function impairment or chronic renal failure.

CONCLUSIONS

These results are consistent with the hypothesis that CMMG is involved in the development of neuropsychiatric side effects in aciclovir- or valaciclovir-treated patients. Measurement of CMMG in CSF and/or serum is a promising tool in the diagnostic procedure for aciclovir- or valaciclovir-treated patients with neuropsychiatric symptoms and may help to differentiate between side effects and herpes encephalitis.

[Encephalopathy and acute renal failure during acyclovir treatment]

INTRODUCTION

Adverse neurological and renal effects can occur in patients taking acyclovir. Neurotoxicity of acyclovir results from an accumulation of the antiviral and its metabolites in the bloodstream. This can be observed in the elderly or in patients with chronic renal failure, generally in dialysis patients. Acute renal failure results from intratubular crystallization of acyclovir.

OBSERVATION

A 78-year-old right-handed woman was admitted in an emergency setting for aphasia. Analysis of the cerebrospinal fluid was normal, but herpetic meningo-encephalitis was suspected and intravenous treatment was initiated with acyclovir. After the second infusion, the patient began to suffer from visual hallucinations, confusion and acute renal failure. Herpes PCR was negative in the cerebrospinal fluid, and the adverse drug reactions regressed completely after 72 hours.

CONCLUSION

Renal function has to be checked often in patients given acyclovir for appropriate dose titration. Patients recover prompt from the adverse effects at drug withdrawal.