Influence of hemodialysis on acyclovir pharmacokinetics in patients with chronic renal failure

An Unusual Neurological Syndrome in a Haemodialysis Patient

Advanced age and immunosuppressed states allow for complications of herpes zoster such as encephalitis. In this case report, we describe a patient with encephalopathy two days after initiation of antiviral therapy. After the necessary imaging and cerebrospinal fluid (CSF) analysis, it became evident that the neurological syndrome was due to acyclovir. Despite currently practised renal dose modification, the patient developed acyclovir-induced neurotoxicity and required intensification of his dialysis schedule to eliminate the drug. Acyclovir-induced neurotoxicity is a rare clinical presentation and presents a clinical dilemma to the physician who has to distinguish this entity from herpes zoster encephalitis and posterior circulation stroke.

A Unique Case of Valacyclovir Toxicity and Pseudobulbar Affect in a Patient On Peritoneal Dialysis

There are a few cases of valacyclovir-associated neurotoxicity (VAN) reported. This case report documents a case of a 55-year-old male presenting with emotional lability or pseudobulbar affect as the predominant or sole manifestation of VAN. A failure to adjust valacyclovir's dose for herpes simplex infection in the setting of dialysis-dependent end-stage renal disease (ESRD) preceded VAN in this patient. The patient presented with involuntary and uncontrollable outbursts of emotion. Computerized tomography (CT) scan identified no underlying cause. A complete neurological examination with cognitive assessment was performed, with no abnormalities. He benefited from the use of aggressive peritoneal dialysis (PD) that was employed to enhance valacyclovir's clearance in this case of intractable VAN. On discharge, the patient was back to baseline mental function. Traumatic brain injury, neoplasm, vascular lesions, metabolic abnormality, neurological disease, herpetic encephalitis, and disorders of mood were ruled out. This led to the hypothesis of encephalopathy due to valacyclovir intoxication. Given that the clinical manifestations were related to ESRD, a dose-adjustment of valacyclovir is imperative in the setting of ESRD to prevent VAN. Our case presents important clinical variations. Firstly, our patient demonstrates that VAN may present with no focal neurological impairment, but pseudobulbar affect. Secondly, aggressive PD was useful in this case for the treatment of VAN as opposed to hemodialysis. We believe that it cleared valacyclovir resulting in the resolution of symptoms.

Novel Insights to Enhance Therapeutics With Acyclovir in the Management of Herpes Simplex Encephalitis

Acyclovir is an antiviral drug poorly absorbed in the gastrointestinal tract due to its hydrophilicity, with low oral bioavailability (~20%). Although acyclovir is prescribed in the management of herpes simplex encephalitis (HSE), the disease has a poor prognosis, particularly if the treatment is delayed, reaching mortality rates of 70% if left untreated. Thus, high acyclovir doses are administered by intravenous (IV) infusion, usually at a dosage of 10 mg kg^-1 8-hourly in adults with normal renal function. However, the mortality related to HSE treated with acyclovir remains high (~20%) and permanent sequelae are commonly reported after 1 year (~50%). This review analyzed clinical trials following IV acyclovir administration. Novel insights aiming to improve drug bioavailability were reviewed, including acyclovir or its prodrugs, leading to the systemic distribution of the drug or drug targeting. Much research effort has been made to improve antiviral therapy, searching for delivery systems increasing acyclovir bioavailability by non-invasive pathways, such as oral and nasal pathways, or parenterally administered nanotechnology-based systems leading to drug targeting. Nanocarriers administered by non-invasive pathways represent feasible alternatives to treat HSE, even though not be industrially manufactured yet.

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.

Status of Hemodialysis of Drugs in 2002

Hemodialysis is a life-sustaining chronic therapy for individuals with end stage renal disease (ESRD). It is also frequently used for days to weeks for patients with acute renal failure who are awaiting the recovery of their kidneys from the acute toxic or traumatic event. Both populations of patients often require complex pharmacotherapeutic regimens, and it is not uncommon for them to be receiving 10 or more concomitant medications. Optimization of care for these patients is dependent on the selection of the most appropriate drug as well as dosage regimen design, which accounts for the influence of hemodialysis therapy on drug disposition. During the last 10 to 15 years there have been several significant changes in the prescribed dose of dialysis and the composition and size of dialyzers available for use. Furthermore, reuse of dialyzers, which was rare in the early 1980s, is now common; it is employed with over 70% of patients with ESRD. The new synthetic dialyzers, which are now used for over 60% of ESRD patients in the United States, are uniformly associated with dramatic improvements in drug removal; dialysis clearance increases of 3 to 10 fold were common for the few drugs evaluated. The influence of these changes in hemodialysis therapy on drug disposition are discussed in a quantitative fashion, and a conceptual framework for drug therapy regimen decision making is presented. For the majority of the drugs reviewed, however, there were no data in the literature regarding dialyzability with currently available dialyzers. The generation of dialyzability data for old and new pharmacotherapeutic agents with state of the art dialysis procedures is clearly needed.

Intensification of peritoneal dialysis improves valacyclovir neurotoxicity

Valacyclovir induced neurotoxicity is a life-threatening complication, usually starting 24-48 h after drug-peak serum concentrations. The elderly with impaired renal function seem to be the most susceptible group to valacyclovir neurotoxicity. Although hemodialysis is considered the best method for rapid drug removal, our case showed that intensive peritoneal dialysis regimen leads to the recovery of neurotoxicity after 3 days.

The use of antiviral drugs during the neonatal period

Parenteral therapy of viral infections of the newborn and infant began with vidarabine (adenine arabinoside) for the treatment of neonatal herpes simplex virus (HSV) infections in the early 1980s. Acyclovir has become the treatment of choice for neonatal HSV infections and a variety of other herpesvirus infections. Ganciclovir is beneficial for the treatment of congenital cytomegalovirus (CMV) infections involving the central nervous system (CNS). This article reviews the use of acyclovir and ganciclovir in the treatment of neonatal HSV and congenital CMV infections. A brief summary precedes a detailed discussion of available established and alternative therapeutics.

Expression of organic anion transporter 2 in the human kidney and its potential role in the tubular secretion of guanine-containing antiviral drugs

The organic anion transporters 1 and 3 (OAT1 and OAT3) and organic cation transporter 2 (OCT2) are important for renal tubular drug secretion. In contrast, evidence for OAT2 expression in the human kidney is limited, and its role in renal drug transport is unknown. Both mRNA (real-time polymerase chain reaction) and protein (Western blotting) for OAT2 were detected in renal cortex from eight donors, and interindividual variability in protein levels was 3-fold. OAT2 protein in the renal cortex was localized (by immunohistochemistry) to the basolateral domain of tubules, as were OAT1 and OAT3. The absolute abundance of OAT2 mRNA was similar to that of OAT1 mRNA and 3-fold higher than that of OCT2 mRNA but 10-fold lower than that of OAT3 mRNA. A previous observation that OAT2 transports cGMP led us to examine whether acyclovir, ganciclovir, and penciclovir are OAT2 substrates; they are guanine-containing antivirals that undergo active tubular secretion. Transport of the antivirals into human embryonic kidney cells was stimulated 10- to 20-fold by expression of OAT2, but there was little to no transport of the antivirals by OAT1, OAT3, or OCT2. The K(m) values for acyclovir, ganciclovir, and penciclovir transport were 94, 264, and 277 μM, respectively, and transport efficiencies were relatively high (6-24 μl · min(-1) · mg protein(-1)). This study provides definitive evidence for the expression of OAT2 in the human kidney and is the first to demonstrate that OAT2, compared with OAT1, OAT3, or OCT2, has a preference for antiviral drugs mainly eliminated in the urine via active secretion.

The epidemiology of drug-induced disorders: the kidney

The epidemiology of drug-induced renal disorders is a complex topic. Drug-associated nephrotoxicity accounts for 18 - 27% of all acute kidney injury cases in US hospitals. Medications can affect all aspects of the kidney, and drugs that are associated with renal dysfunction are used commonly in clinical practice. The article reviews six major mechanisms of drug-induced renal dysfunction as well as lists the major medications involved. NSAIDs, aminoglycosides, amphotericin B and calcineurin inhibitors are just some examples of drugs that contribute to renal dysfunction. The medical community must be aware of patient risk factors for nephrotoxicity, as well as the drug's inherent nephrotoxic potential, when prescribing and administering medications.

[One episode of meningoencephalitis, three diagnoses]

Meningo-encephalitis is a set of threatening diseases. The treatment needs to be started quickly for pathogens such as herpes simplex virus type 1 or Listeria monocytogenes. Apart from these classical etiologies, many other diseases may induce meningo-encephalitis. We report the case of a patient, infected with HIV, who presented a history of meningo-encephalitis due to herpes simplex type 1. Three weeks later, he presented an encephalopathy due to aciclovir and then we discovered a chronic meningitis in relation with his HIV infection.

Drug-Associated Renal Dysfunction

Acute renal failure (ARF) in patients in the ICU is associated with a high mortality. Drug-induced renal dysfunction is an important, yet often overlooked, cause of ARF in this patient population. A drug use evaluation at the authors' institution, to assess the prescribing patterns of potential nephrotoxins in the adult and pediatric ICUs, found that antibiotics (aminoglycosides, amphotericin B, penicillins, cephalosporins, acyclovir), nonsteroidal anti-inflammatory drugs, contrast dye, and various other nephrotoxic medications are used widely in all of the ICUs. By focusing on several commonly prescribed classes of nephrotoxic medications in the ICU, this article reviews the general mechanisms of drug-associated renal dysfunction.

Adverse neuropsychiatric effects of cytomegalovirus prophylaxis with valaciclovir in renal transplant recipients

BACKGROUND

Valaciclovir (VACV) has been reported to induce adverse neuropsychiatric effects (ANE), especially in patients with renal failure, but few data are available for renal transplant recipients (RTR).

METHODS

We conducted a retrospective study in RTR given VACV as cytomegalovirus prophylaxis, from January 1999 to December 2000, to define the incidence rate, type and outcome of VACV-induced ANE, and to identify risk factors for ANE. The VACV-induced ANE were defined as neuropsychiatric disorders justifying VACV dose reduction or withdrawal. Patients with and without VACV-induced ANE were compared by univariate and multivariate analysis.

RESULTS

In all, 167 RTR were included, of whom 25 (15%) displayed VACV-induced ANE (mainly hallucinations and confusion), which occurred with a mean of 4 days after the start of VACV. ANE were reversible in all cases. Multivariate analysis showed that delayed graft function (DGF) was the main risk factor for VACV-induced ANE [Odds ratio (OR): 12.1; 95% CI = 3.4-43.4; P = 0.0001]. All VACV doses given to patients with ANE were in accordance with the current recommended adaptation to estimated glomerular filtration rate (GFR).

CONCLUSION

In RTR, VACV-induced ANE are significantly frequent but reversible. DGF occurrence is the main risk factor for these ANE. In RTR with DGF, the recommended doses for GFR below 10 ml/min might be too high. Several strategies, in RTR with DGF, might lower the risk of ANE, including reduction of the currently recommended VACV dosage, delayed VACV introduction until improvement of renal function, or use of another anti-cytomegalovirus drug.

[Cerebral and renal toxicity of acyclovir in a patient treated for meningoencephalitis]

We report the case of a 65-year-old man treated with intravenous acyclovir and amoxicilline for meningoencephalitis. Six days later, he suddenly developed acute renal failure, associated with central nervous system symptoms. The high acyclovir concentration in plasma and spinal fluid confirmed the hypothesis of acyclovir toxicity. Continuous haemofiltration resulted in a rapid amendment of neurologic and renal symptoms. Despite the high therapeutic index of acyclovir, manifestations of neurotoxicity and nephrotoxicity are not a rare event. The risk is increased in the elderly and in patients with renal insufficiency. Rapid intravenous injections are contraindicated. Continuous haemofiltration is rapidly efficient. The value of acyclovir concentration determination in plasma and spinal fluid are stressed.

Herpes zoster associated encephalitis in dialysis patients

Two patients on dialysis because of chronic renal failure who developed herpes zoster associated encephalitis are reported. Both developed overt encephalopathy despite treatment with oral acyclovir for the preceding herpes zoster eruption. The encephalopathy responded rapidly to intravenous acyclovir.

Intraperitoneal administration of acyclovir in patients receiving continuous ambulatory peritoneal dialysis

In subjects with normal renal function, acyclovir is rapidly removed from the body via the kidneys. In subjects with end-stage renal disease, the half-life is significantly prolonged. The half-life in subjects receiving hemodialysis and continuous ambulatory peritoneal dialysis (CAPD) is similarly prolonged (10.0 +/- 2.2 and 13.2 +/- 4.7 hours, respectively). After intravenous dosage, peritoneal clearance was 3.4 +/- 0.2 mL/min. Intraperitoneal dosing in subjects receiving CAPD resulted in a bioavailability of 61 +/- 10% and drug levels sufficient to inhibit herpes simplex virus (HSV) and varicella zoster virus (VZV). Intraperitoneal administration is an alternative route of administration in patients with poor vascular access.

Antiviral agents

Potent effective antiviral drugs recently have been licensed for several viral diseases, ushering in a new era in the treatment of viral diseases. Several unique features in the process of a viral infection have been identified as target points for inhibition. The unique steps and the interfering compounds are the subject of this review.

Acyclovir pharmacokinetics in a patient on continuous ambulatory peritoneal dialysis

Acyclovir is an effective agent for the treatment of herpes virus infections, however, the pharmacokinetics of the drug are altered in renal failure. We studied this drug in a continuous ambulatory peritoneal dialysis (CAPD) patient who was immunocompromised and had cutaneous herpes infection. The elimination half-life (17.1 hours) was similar to that reported for end-stage renal disease (ESRD) patients, while the volume of the central compartment (29.6 L/1.73 m2), the steady state volume of distribution (68.1 L/1.73 m2), and the total body clearance (48.3 mL/min/1.73 m2) were greater. The mean CAPD clearance was only 4.4 mL/min, with less than 10% of an administered dose being recovered in the 24-hour dialysate. Further studies are needed to establish a dosing regimen for CAPD patients.

Drug prescribing in renal failure: dosing guidelines for adults

The data base for rational guidelines to safe, efficacious drug prescribing in adults with renal insufficiency are presented in tabular form. Current medical literature was extensively surveyed to provide as much specific information as possible. When information is lacking, however, recommendations are based on pharmacokinetic variables in normal subjects. Nephrotoxicity, important adverse effects, and special considerations in renal patients are noted. Adjustments are suggested for hemodialysis and peritoneal dialysis when appropriate.

The clinical use of intravenous acyclovir

Acyclovir (acycloguanosine) is a new antiviral compound with activity against certain herpes viruses. Acyclovir is phosphorylated preferentially in virus-infected cells into its active form, acyclovir triphosphate, an inhibitor of viral-induced DNA polymerase. Acyclovir, which possesses an acyclic carbohydrate moiety, also causes premature DNA chain termination. Acyclovir has shown clinical activity against herpes simplex virus (HSV) types 1 and 2 and varicella zoster virus (VZV), but its usefulness in cytomegalovirus, Epstein-Barr virus, and chronic hepatitis B infections requires further study. In randomized clinical trials of infections caused by HSV and VZV, intravenous acyclovir has been shown to shorten the duration of viral shedding and lesion pain and hasten the resolution of skin lesions, with minimal toxicity.

Acyclovir clinical pharmacology. An overview

The current status of pharmacokinetic and toxicologic information on acyclovir is reviewed from a clinical pharmacologist's perspective. Acyclovir pharmacokinetics is accurately described by a two-compartment open model. The volume of distribution at steady state is about two-thirds of the body weight. The half-life of its beta phase of elimination is about three hours with normal renal function and increases to about 18 hours with anuria. Hemodialysis removes about 60 percent of the acyclovir in the body. The pharmacokinetics is independent of dose at least up to 15 mg/kg. Acyclovir is minimally (15 percent) protein-bound an only a small percentage (15 percent) of an intravenous dose is metabolized in persons with normal renal function. Acyclovir is eliminated primarily by glomerular filtration with a small addition from tubular secretion. The toxicity of acyclovir seems to be acceptably low. Local irritation with extravasation exists. Transient glomerular dysfunction is occasionally seen after bolus administration. Other side effects remain to be clearly established.