Valaciclovir: a review of its use in the management of herpes zoster

Synthesis of Selenium-Decorated N-Oxide Isoquinolines: Arylseleninic Acids in Selenocyclization Reactions

Herein, we describe the use of benzeneseleninic acid derivatives (BSA) as a bench-stable and easy to handle selenium reagent to access 4-(selanyl)isoquinoline-N-oxides through the selenocyclization of o-alkynyl benzaldehyde oximes. The reaction is conducted in refluxing methanol, allowing the thermal generation of electrophilic selenium species in situ. By this new protocol, a library of 19 selenium-decorated N-oxide isoquinolines was accessed in up to 96% yield with an outstanding substrate tolerance and the feasibility to scale it up 10 times (from 0.25 to 2.5 mmol).

Herpes zoster ophthalmicus

Herpes zoster ophthalmicus (HZO) occurs when latent varicella zoster virus reactivates in the ophthalmic division of the fifth cranial nerve (CNV1). HZO commonly affects older and immunocompromised patients. This disease is considered an ophthalmic emergency due to the wide range of associated ocular symptoms, including severe chronic pain and vision loss. HZO is typically a clinical diagnosis due to its classic presentation of a unilateral vesicular eruption in the dermatomes corresponding to CNV1. Timely treatment is imperative to minimize ocular morbidity in HZO, given that ocular involvement is present in 50% of affected patients.

Herpes simplex virus, varicella-zoster virus and cytomegalovirus keratitis: Facts for the clinician

Keratitis due to Herpes simplex virus (HSK), Varicella-Zoster virus (VZK) and Cytomegalovirus remains a frequent source of concern for many ophthalmologists. They are a frequent cause of emergency consultations at eye care centers and carry the risk of permanent loss of visual acuity or visual quality and/or chronic neurotrophic keratitis, resulting in a significant decrease in the quality of life. HSK and VZK can affect the corneal epithelium, stroma, or endothelium or a combination of layers. In contrast, most cases of CMV keratitis present as isolated endothelitis (CMVE), a clinical entity that has been described within the last 2 decades. These three types of viral keratitis are characterized by a high frequency of recurrences and each new episode increases the risk of sequelae. Hence, ophthalmologists must adapt the treatment to the clinical presentation of each recurrent episode in order to mitigate the immediate consequences of viral replication and the immune response on corneal transparency. In patients with frequent recurrences, preventive long-term antiviral treatment is strongly recommended. However, in some rare cases, continuous exposure to antivirals may promote the emergence of resistant viral strains, which can be difficult to manage. In the future, the introduction of new antiviral drugs, with differing modes of action compared to current medical therapy, could be an alternative until a truly effective preventive solution, such as a vaccine, is available.

Comparing Prodrugs with Acyclovir for Treating Postherpetic Neuralgia among Herpes Zoster Patients: A Systematic Review and Meta-Analysis

Postherpetic neuralgia (PHN) is a common, painful, and long-term complication of herpes zoster (HZ). PHN increases the demand for healthcare services and, previous studies showed that patients who received antiviral agents were less likely to develop PHN. The objective of this study was to compare the efficacy of prodrugs and acyclovir in treating PHN among patients with HZ. The search included the PubMed, Medline, Embase, and Cochrane Center of Register of Controlled Trails databases through February 2022. Clinical trials and randomized controlled trials (RCTs) involving antiviral agent intervention for HZ patients diagnosed with PHN were eligible for inclusion. A meta-analysis was conducted to calculate pooled risk ratios (RRs) with 95% confidence intervals (CIs) with a fix-effect model. Five RCTs with 1147 HZ patients met our eligibility criteria. Our meta-analysis found that there was a significantly lower risk of PHN for members of the prodrugs group (famciclovir and valaciclovir) compared with those who received acyclovir (RR = 0.86, 95%, CI: 0.75 to 0.98, p = 0.03). The review of studies indicated that the efficacy of prodrugs was better than acyclovir for reliving PHN.

Concurrent Nephrotoxicity and Neurotoxicity Induced by Oral Valacyclovir in a Patient With Previously Normal Kidney Function

Drug-induced nephrotoxicity and neurotoxicity are commonly encountered problems in clinical practice. We describe a case of concurrent valacyclovir-induced nephrotoxicity and neurotoxicity in a 64-year-old man with no history of renal disease who developed acute renal injury and neurological symptoms after he received two weeks of the standard dose of oral valacyclovir for herpes zoster meningitis. His clinical condition improved significantly after the initiation of hemodialysis. Although nephrotoxicity due to intravenous infusion of valacyclovir and/or acyclovir is not uncommon, oral valacyclovir therapy is rarely associated with nephrotoxicity in patients with no history of renal insufficiency. Additionally, concurrent nephrotoxicity and neurotoxicity due to valacyclovir and/or acyclovir are rarely reported. Clinicians should be aware of these adverse events as immediate recognition and intervention are necessary to prevent morbidity.

Targeting ectromelia virus and TNF/NF-κB or STAT3 signaling for effective treatment of viral pneumonia

Viral causes of pneumonia pose constant threats to global public health, but there are no specific treatments currently available for the condition. Antivirals are ineffective when administered late after the onset of symptoms. Pneumonia is caused by an exaggerated inflammatory cytokine response to infection, but tissue necrosis and damage caused by virus also contribute to lung pathology. We hypothesized that viral pneumonia can be treated effectively if both virus and inflammation are simultaneously targeted. Combined treatment with the antiviral drug cidofovir and etanercept, which targets tumor necrosis factor (TNF), down-regulated nuclear factor kappa B-signaling and effectively reduced morbidity and mortality during respiratory ectromelia virus (ECTV) infection in mice even when treatment was initiated after onset of clinical signs. Treatment with cidofovir alone reduced viral load, but animals died from severe lung pathology. Treatment with etanercept had no effect on viral load but diminished levels of inflammatory cytokines and chemokines including TNF, IL-6, IL-1β, IL-12p40, TGF-β, and CCL5 and dampened activation of the STAT3 cytokine-signaling pathway, which transduces signals from multiple cytokines implicated in lung pathology. Consequently, combined treatment with a STAT3 inhibitor and cidofovir was effective in improving clinical disease and lung pathology in ECTV-infected mice. Thus, the simultaneous targeting of virus and a specific inflammatory cytokine or cytokine-signaling pathway is effective in the treatment of pneumonia. This approach might be applicable to pneumonia caused by emerging and re-emerging viruses, like seasonal and pandemic influenza A virus strains and severe acute respiratory syndrome coronavirus 2.

Enzyme Models-From Catalysis to Prodrugs

Enzymes are highly specific biological catalysts that accelerate the rate of chemical reactions within the cell. Our knowledge of how enzymes work remains incomplete. Computational methodologies such as molecular mechanics (MM) and quantum mechanical (QM) methods play an important role in elucidating the detailed mechanisms of enzymatic reactions where experimental research measurements are not possible. Theories invoked by a variety of scientists indicate that enzymes work as structural scaffolds that serve to bring together and orient the reactants so that the reaction can proceed with minimum energy. Enzyme models can be utilized for mimicking enzyme catalysis and the development of novel prodrugs. Prodrugs are used to enhance the pharmacokinetics of drugs; classical prodrug approaches focus on alternating the physicochemical properties, while chemical modern approaches are based on the knowledge gained from the chemistry of enzyme models and correlations between experimental and calculated rate values of intramolecular processes (enzyme models). A large number of prodrugs have been designed and developed to improve the effectiveness and pharmacokinetics of commonly used drugs, such as anti-Parkinson (dopamine), antiviral (acyclovir), antimalarial (atovaquone), anticancer (azanucleosides), antifibrinolytic (tranexamic acid), antihyperlipidemia (statins), vasoconstrictors (phenylephrine), antihypertension (atenolol), antibacterial agents (amoxicillin, cephalexin, and cefuroxime axetil), paracetamol, and guaifenesin. This article describes the works done on enzyme models and the computational methods used to understand enzyme catalysis and to help in the development of efficient prodrugs.

Different dosages of valaciclovir for the treatment of herpes zoster in adults: A randomized clinical study

WHAT IS KNOWN AND OBJECTIVE

The dosages of valaciclovir used for herpes zoster treatment recommended by Chinese pharmaceutical companies can differ considerably from those reported in the literature. This randomized clinical study compares the efficacy and safety of different oral valaciclovir doses for the treatment of herpes zoster in adults.

METHODS

A total of 214 patients with herpes zoster were enrolled and randomized into two groups according to age: 98 patients in the 18-44-year group (younger patients) and 116 patients in the 45-74-year group (middle-aged and elderly patients). Patients in the two age groups were then prescribed different doses of valaciclovir. The high-dose group was administered 900 mg of valaciclovir, three times daily for 10 days, whereas the low-dose group was administered 300 mg of valaciclovir, two times daily for 10 days. The efficacy and side effects of these regimens were recorded on days 6, 11 and 30.

RESULTS

In total, 207 (of 214 enrolled) patients completed the study. Of the seven patients who discontinued the study, five discontinued because their follow-up time was not fixed and two withdrew after moving to other cities. At the 11th day after treatment, the clinical effect of high-dose valaciclovir groups were significantly better than that of the low-dose valaciclovir groups in middle-aged and elderly patients (p < 0.05). The difference in visual analog scale (VAS) pain scores between the two dose groups was statistically significant in middle-aged and elderly patients at the 6th day(p < 0.05), whereas there was no difference in younger patients (p > 0.05). The VAS scores were significantly lower in high-dose group than in low-dose group at day 11 in both groups of patients(p < 0.05).There was no statistically significant difference in the time to skin scab improvement between the two different dose groups in younger patients (p > 0.05). Among middle-aged and elderly patients, the incidence of postherpetic neuralgia (PHN) was significantly lower in the high-dose group than in the low-dose group (p < 0.05). The difference in the incidence of adverse reactions between the high-dose and low-dose groups was not statistically significant (p > 0.05). Overall, the main side effect was headache.

WHAT IS NEW AND CONCLUSION

The present study indicates that early treatment with high-dose valaciclovir can significantly reduce pain in patients, especially in elderly patients, in whom it can also reduce the incidence of PHN. In terms of safety, no significant difference was noted in the incidence of adverse reactions between high- and low-dose groups.

Neurological and Ophthalmological Manifestations of Varicella Zoster Virus

BACKGROUND

Approximately 1 million new cases of herpes zoster (HZ) occur in the United States annually, including 10%-20% with herpes zoster ophthalmicus (HZO). Postherpetic neuralgia, a debilitating pain syndrome occurs in 30% HZ, whereas 50% HZO develop ophthalmic complications. Diplopia from cranial nerve palsy occurs in less than 30% HZO, whereas optic neuropathy is seen in less than 1% HZO. We reviewed recent developments in the diagnosis, treatment, and prevention of HZ as well as neurological and ophthalmological complications of relevance to the neuro-ophthalmologist.

EVIDENCE ACQUISITION

We searched the English language literature on Pubmed and Google scholar for articles relevant to the various sections of this review.

RESULTS

Antiviral treatment should be initiated within 48-72 hours of onset of HZ and HZO to decrease pain and reduce complications. We recommend neuroimaging in all patients with neuro-ophthalmic manifestations such as diplopia and acute vision loss. Diagnostic confirmation using polymerase chain reaction and serology on paired serum and cerebrospinal fluid samples should be obtained in those with neurological signs and symptoms or abnormal imaging. Patients with neurological and/or retinal varicella zoster virus (VZV) infection should be treated promptly with intravenous acyclovir. Patients with isolated optic neuropathy or cranial nerve palsy can be managed with oral antivirals. The prognosis for visual recovery is good for patients with isolated optic neuropathy and excellent for patients with isolated ocular motor cranial nerve palsy.

CONCLUSIONS

HZ produces a spectrum of potentially blinding and life-threatening complications that adversely affect quality of life and increase health care costs. Individuals at risk for HZ, such as the elderly and immunocompromised, should be encouraged to receive the highly effective VZV vaccine to prevent HZ and its complications.

Herpes Zoster Presentation, Management, and Prevention: A Modern Case-Based Review

Herpes zoster (HZ) is a common cutaneous entity with protean clinical presentations, management options, complication rates, and prevention strategies, all of which are rife with dogma. During an inpatient consultation for HZ, have you ever been approached by a frantic staff or family member, worried that a pregnant, elderly, or infant contact will be 'infected' if they get too close? Have your patients ever asked you about their risk of having HZ twice, or claimed that they have frequent 'recurrences'? In what timeline should antiviral therapy be employed? Is there evidence for prednisone or gabapentin in acute HZ treatment? Who should be vaccinated against HZ and what are the benefits and risks? In case-based form, these and other complex but common scenarios will be examined using clinical and viral mechanistic clues, along with updated treatment and prevention guidelines, to provide a modern HZ case management compendium, comprehensive of the diverse age and health populations now presenting with this condition.

Varicella Zoster aseptic meningitis: Report of an atypical case in an immunocompetent patient treated with oral valacyclovir

Varicella Zoster when described has the typical presentation of a dermatomal distribution of a rash and can further lead to CNS complications. This can be treated accordingly with the proper protocol, but if the presentation is atypical and the protocol is challenged or changed per specific patient outcomes, new developments can occur. Here we present a case of a 29-year-old Caucasian female that presented to the emergency department with headache, photophobia, and chills for 5 days. She was previously healthy and immunocompetent; CSF PCR analysis revealed a VZV infection causing acute aseptic meningitis with no shingles rash eruption on physical examination. The patient was not willing to stay hospitalized for the duration of the treatment. This gave us an opportunity to treat her with an oral, rather than IV, antiviral. The patient was successfully treated with oral valacyclovir 2 g Q6H after only receiving two days of IV acyclovir. To the best of our knowledge, this is the first reported case of a patient with VZV-associated meningitis successfully treated with oral valacyclovir.

Valacyclovir Neurotoxicity and Nephrotoxicity in an Elderly Patient Complicated by Hyponatremia

A 66-year-old women with no history of renal disease was admitted due to a coma and acute kidney injury with a serum creatinine level of 7.44 mg/dL which were ascribed to valacyclovir neurotoxicity and nephrotoxicity, respectively. She had received valacyclovir at a standard dosage for the treatment of herpes zoster and was finally discharged, having fully returned to her normal baseline mental status with a recovered serum creatinine level of 0.68 mg/dL. We feel that awareness of this pathology remains a challenge for physicians and therefore strongly recommend the further accumulation of experiences similar to our own. Our experience underscores the pitfalls of administering valacyclovir to elderly patients who barely appear to have a favorable renal function. Several concerns regarding the therapeutic management, including blood purification strategies, that emerged in this case are also discussed.

A sensitive liquid chromatography-tandem mass spectrometry method for the quantification of valacyclovir and its metabolite acyclovir in mouse and human plasma

It is challenging to conduct a pharmacokinetic (PK) study on mice due to the limited amount of plasma one can obtain, which is also true for some clinical studies. Here, we developed and validated a simple, sensitive and robust LC-MS/MS method for measuring the prodrug valacyclovir (VACV) and its metabolite acyclovir (ACV) in mouse and human plasma. This assay utilized an acetonitrile protein precipitation method with isotope-labeled internal standards (IS) and enabled precise and accurate quantification of VACV and ACV in 10 μL plasma samples with a nine-min gradient. The analytes were separated on a Waters Atlantis T3 C18 column. The precursor-product ion transitions for VACV (m/z 325.2 > 152.1), ACV (m/z 226.2 > 152.1), VACV-D4 (m/z 329.2 > 152.1, IS) and ACV-D4 (m/z 230.2 > 152.1, IS) were detected in a multiple reaction monitoring (MRM) positive ion mode using an API4000 LC-MS/MS system. The lower limit of quantification (LLOQ) was 2 nM for both VACV and ACV. The linear range was validated over the concentration ranges of 2-200 nM and 200-5000 nM for both compounds. The matrix effect and stability of VACV and ACV were also evaluated. This assay was successfully applied to a PK study in mice.

Treatment of herpes zoster ophthalmicus: a systematic review and Canadian cost-comparison

OBJECTIVE

A systematic review and cost comparison were conducted to determine the optimal treatment of active herpes zoster ophthalmicus (HZO) in immunocompetent adults.

DESIGN

A literature search of MEDLINE, EMBASE, CINAHL, Cochrane Library, BIOSIS Previews and Web of Science, ClinicalTrials.gov, International Clinical Trials Registry Platform, Networked Digital Library of Theses and Dissertations, and Canadian Health Research Collection was performed. The search period was from January 1990 to March 2017.

PARTICIPANTS

Collectively, 516 immunocompetent patients with active HZO treated with oral antivirals were included.

METHODS

Randomized controlled trials (RCTs) investigating treatment of active HZO in immunocompetent adults, with one oral acyclovir monotherapy arm, were included. Studies fulfilling inclusion criteria were subjected to quality assessment and data extraction. Provincial drug formularies were consulted to extrapolate cost comparison for investigated treatment regimens.

RESULTS

A total of 1515 titles and abstracts and 9 full-text articles were assessed. Three RCTs met the inclusion criteria. Treatment with oral acyclovir (800 mg 5 times daily for 10 days) was superior to placebo in the prevention of ocular manifestations. Oral famciclovir (500 mg 3 times daily for 7 days) and valacyclovir (1000 mg 3 times daily for 7 days) resulted in comparable rates of ocular manifestations relative to oral acyclovir (800 mg 5 times daily for 7 days). According to provincial drug formulary data, famciclovir and valacyclovir are more affordable across Canada with the recommended dosing schedules.

CONCLUSIONS

Oral famciclovir and valacyclovir are reasonable alternatives to oral acyclovir for treatment of active HZO in immunocompetent individuals. Their simpler dosing schedules are associated with a cost benefit that is consistent across Canada.

In Silico Absorption Analysis of Valacyclovir in Wildtype and Pept1 Knockout Mice Following Oral Dose Escalation

PURPOSE

We developed simulation and modeling methods to predict the in vivo pharmacokinetic profiles of acyclovir, following escalating oral doses of valacyclovir, in wildtype and Pept1 knockout mice. We also quantitated the contribution of specific intestinal segments in the absorption of valacyclovir in these mice.

METHODS

Simulations were conducted using a mechanistic advanced compartmental absorption and transit (ACAT) model implemented in GastroPlus™. Simulations were performed for 3 h post-dose in wildtype and Pept1 knockout mice following single oral doses of 10, 25, 50 and 100 nmol/g valacyclovir, and compared to experimentally observed plasma concentration-time profiles of acyclovir.

RESULTS

Good fits were obtained in wildtype and Pept1 knockout mice. Valacyclovir was primarily absorbed from duodenum (42%) and jejunum (24%) of wildtype mice, with reduced uptake from ileum (3%) and caecum/colon (1%), for a total of 70% absorption. In contrast, the absorption of valacyclovir in Pept1 knockout mice was slow and sustained throughout the entire intestinal tract in which duodenum (4%), jejunum (14%), ileum (10%) and caecum/colon (12%) accounted for a total of 40% absorption.

CONCLUSION

The ACAT model bridged the gap between in situ and in vivo experimental findings, and facilitated our understanding of the complicated intestinal absorption processes of valacyclovir.

Bilateral herpes zoster in a patient with end-stage kidney disease

Herpes zoster (HZ) is caused by the reactivation of a latent varicella-zoster virus (VZV) infection within the cranial or dorsal root ganglia. The cutaneous lesions of HZ are typically limited to a single dermatome, while non-contiguous HZ involving two or more dermatomes is a very rare clinical entity. In this report, we describe a case of HZ involving the left and right side of the abdomen corresponding to the T11 dermatome in a 63-year-old man on chronic peritoneal dialysis. The characteristic cutaneous manifestation encouraged us to ascribe the disease to HZ duplex bilateralis, and the patient was given a single dose of oral valacyclovir and achieved a favorable outcome. The therapeutic concerns regarding the reactivation of VZV in patients with end-stage kidney disease are also discussed.

Valacyclovir versus acyclovir for the treatment of herpes zoster ophthalmicus in immunocompetent patients

BACKGROUND

Herpes zoster ophthalmicus affects the eye and vision, and is caused by the reactivation of the varicella zoster virus in the distribution of the first division of the trigeminal nerve. An aggressive management of acute herpes zoster ophthalmicus with systemic antiviral medication is generally recommended as the standard first-line treatment for herpes zoster ophthalmicus infections. Both acyclovir and its prodrug valacyclovir are medications that are approved for the systemic treatment of herpes zoster. Although it is known that valacyclovir has an improved bioavailability and steadier plasma concentration, it is currently unclear as to whether this leads to better treatment results and less ocular complications.

OBJECTIVES

To assess the effects of valacyclovir versus acyclovir for the systemic antiviral treatment of herpes zoster ophthalmicus in immunocompetent patients.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register; 2016, Issue 5), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to June 2016), Embase (January 1980 to June 2016), Web of Science Conference Proceedings Citation Index-Science (CPCI-S; January 1990 to June 2016), BIOSIS Previews (January 1969 to June 2016), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov), and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP; www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 13 June 2016.

SELECTION CRITERIA

We considered all randomised controlled trials (RCTs) in which systemic valacyclovir was compared to systemic acyclovir medication for treatment of herpes zoster ophthalmicus. There were no language restrictions.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, evaluated the risk of bias in included trials, and extracted and analysed data. We did not conduct a meta-analysis, as only one study was included. We assessed the certainty of the evidence for the selected outcomes using the GRADE approach.

MAIN RESULTS

One study fulfilled the inclusion criteria. In this multicentre, randomised double-masked study carried out in France, 110 immunocompetent people with herpes zoster ophthalmicus, diagnosed within 72 hours of skin eruption, were treated, with 56 participants allocated to the valacyclovir group and 54 to the acyclovir group. The study was poorly reported and we judged it to be unclear risk of bias for most domains.Persistent ocular lesions after 6 months were observed in 2/56 people in the valacyclovir group compared with 1/54 people in the acyclovir group (risk ratio (RR) 1.93 (95% CI 0.18 to 20.65); very low certainty evidence. Dendritic ulcer appeared in 3/56 patients treated with valacyclovir, while 1/54 suffered in the acyclovir group (RR 2.89; 95% confidence interval (CI) 0.31 to 26.96); very low certainty evidence), uveitis in 7/56 people in the valacyclovir group compared with 9/54 in the acyclovir group (RR 0.96; 95% CI 0.36 to 2.57); very low certainty evidence). Similarly, there was uncertainty as to the comparative effects of these two treatments on post-herpetic pain, and side effects (vomiting, eyelid or facial edema, disseminated zoster). Due to concerns about imprecision (small number of events and large confidence intervals) and study limitations, the certainty of evidence using the GRADE approach was rated as low to very low for the use of valacyclovir compared to acyclovir.

AUTHORS' CONCLUSIONS

This review included data from only one study, which had methodological limitations. As such, our results indicated uncertainty of the relative benefits and harms of valacyclovir over acyclovir in herpes zoster ophthalmicus, despite its widespread use for this condition. Further well-designed and adequately powered trials are needed. These trials should include outcomes important to patients, including compliance.

Valacyclovir and Postherpetic Neuralgia

Objective:

To describe the role of valacyclovir in the treatment of acute herpes zoster pain and its effect in postherpetic neuralgia.

Data Sources:

A literature search was conducted on MEDLINE (1980–October 2003). Search terms included valacyclovir, postherpetic neuralgia, treatment, acyclovir, and valacyclovir.

Study Selection and Data Extraction:

Articles describing use of valacyclovir in the treatment of herpes zoster, with focus upon alleviation of acute zoster pain and postherpetic neuralgia, and articles describing use of valacyclovir for this indication in comparison with other antivirals were evaluated.

Data Synthesis:

Four studies discussing the use of valacyclovir in the treatment of herpes zoster with focus on herpetic pain and postherpetic neuralgia were identified. All of these studies reported that valacyclovir is an effective treatment for herpes zoster and alleviates associated pain significantly faster than acyclovir, presumably due to its greater bioavailability. Valacyclovir likely results in a higher adherence rate than acyclovir because it is dosed 3 versus 5 times daily. Interestingly, the severity of pain was not significantly different between the 2 treatments, only the duration. Finally, one study showed that valacyclovir is equally as effective as famciclovir in alleviating pain associated with herpes zoster.

Conclusions:

Valacyclovir 1 g given orally 3 times a day for 7 days is effective in the treatment of herpes zoster. It is superior to acyclovir 800 mg given orally 5 times a day for 7 days and equivalent to famciclovir 500 mg given orally 3 times a day for 7 days in alleviating acute zoster pain and postherpetic neuralgia.

The efficacy and cost-effectiveness of valacyclovir in cytomegalovirus prevention in solid organ transplantation

Prevention of cytomegalovirus infection using antiviral prophylaxis or the pre-emptive therapy approach is an integral part of management of patients after solid organ transplantation. Regarding renal transplantation, valacyclovir is currently the only antiviral agent recommended for prophylaxis as an alternative to valganciclovir. This review article discusses studies documenting the efficacy and safety of valacyclovir prophylaxis as well as those comparing valacyclovir with other prophylactic regimens or with pre-emptive therapy. Also addressed are the economic aspects supporting the cost-effectiveness of valacyclovir prophylaxis and demonstrating lower costs compared with other cytomegalovirus preventive strategies.

Impact of peptide transporter 1 on the intestinal absorption and pharmacokinetics of valacyclovir after oral dose escalation in wild-type and PepT1 knockout mice

The primary objective of this study was to determine the in vivo absorption properties of valacyclovir, including the potential for saturable proton-coupled oligopeptide transporter 1 (PepT1)-mediated intestinal uptake, after escalating oral doses of prodrug within the clinical dose range. A secondary aim was to characterize the role of PepT1 on the tissue distribution of its active metabolite, acyclovir. [³H]Valacyclovir was administered to wild-type (WT) and PepT1 knockout (KO) mice by oral gavage at doses of 10, 25, 50, and 100 nmol/g. Serial blood samples were collected over 180 minutes, and tissue distribution studies were performed 20 minutes after a 25-nmol/g oral dose of valacyclovir. We found that the C(max) and area under the curve (AUC)₀₋₁₈₀ of acyclovir were 4- to 6-fold and 2- to 3-fold lower, respectively, in KO mice for all four oral doses of valacyclovir. The time to peak concentration of acyclovir was 3- to 10-fold longer in KO compared with WT mice. There was dose proportionality in the C(max) and AUC₀₋₁₈₀ of acyclovir in WT and KO mice over the valacyclovir oral dose range of 10-100 nmol/g (i.e., linear absorption kinetics). No differences were observed in the peripheral tissue distribution of acyclovir once these tissues were adjusted for differences in perfusing drug concentrations in the systemic circulation. In contrast, some differences were observed between genotypes in the concentrations of acyclovir in the distal intestine. Collectively, the findings demonstrate a critical role of intestinal PepT1 in improving the rate and extent of oral absorption for valacyclovir. Moreover, this study provides definitive evidence for the rational development of a PepT1-targeted prodrug strategy.

Single-day treatment for orolabial and genital herpes: a brief review of pathogenesis and pharmacology

Herpes simplex virus (HSV) infection is a highly prevalent condition responsible for significant morbidity and occasional mortality each year. Approximately half of all patients infected by HSV will experience at least one recurrence in their lifetime. For these recurrences, traditional therapy has included both suppressive and episodic treatment with nucleoside analogs. In regards to episodic treatment, 2- to 5-day oral regimens are best studied and most commonly reported. As with any medical condition having a well-understood mechanism of action and targeted treatment, therapeutic intervention is only as effective as allowed by patient compliance. Based on these concerns, recent studies have focused on shorter, less complicated, and more affordable options. This review delineates the evidence for single-day treatments of orolabial and genital herpes. Randomized, double-blind studies of both valacyclovir and famciclovir as single-day episodic therapy for HSV have been reported in the literature. Although no head-to-head studies between the drugs have been performed, both regimens produced significant improvement in healing time and symptom resolution over placebo. Single-day therapy for HSV infection is appealing for multiple reasons. First, it simplifies the regimen, increasing likelihood of patient compliance. Additionally, it allows complete delivery of the medication at the onset of symptoms, when viral replication is highest and intervention has greatest effect. Lastly, the reduced number of pills necessary for single versus multiple day therapy decreases the overall cost of treatment per episode, an important factor in modern-day healthcare.

Herpes zoster ophthalmicus

OPINION STATEMENT

The management of herpes zoster (HZ) usually involves a multidisciplinary approach aiming to reduce complications and morbidity. Patients with herpes zoster ophthalmicus (HZO) are referred to ophthalmologists for prevention or treatment of its potential complications. Without prompt detection and treatment, HZO can lead to substantial visual disability. In our practice, we usually evaluate patients with HZO for corneal complications such as epithelial, stromal, and disciform keratitis; anterior uveitis; necrotizing retinitis; and cranial nerve palsies in relation to the eye. These are acute and usually sight-threatening. We recommend oral acyclovir in conjunction with topical 3% acyclovir ointment, lubricants, and steroids for conjunctival, corneal, and uveal inflammation associated with HZO. Persistent vasculitis and neuritis may result in chronic ocular complications, the most important of which are neurotrophic keratitis, mucus plaque keratitis, and lipid degeneration of corneal scars. Postherpetic complications, especially postherpetic neuralgia (PHN), are observed in well over half of patients with HZO. The severe, debilitating, chronic pain of PHN is treated locally with cold compresses and lidocaine cream (5%). These patients also receive systemic treatment with NSAIDs, and our medical colleagues cooperate in managing their depression and excruciating pain. Pain is the predominant symptom in all phases of HZ disease, being reported by up to 90% of patients. Ocular surgery for HZO-related complications is performed only after adequately stabilizing pre-existing ocular inflammation, raised intraocular pressure, dry eye, neurotrophic keratitis, and lagophthalmos. Cranial nerve palsies are common and most often involve the facial nerve, although palsy of the oculomotor, trochlear, and abducens nerves may occur in isolation or (rarely) simultaneously. In our setting, complete ophthalmoplegia is seen more often than isolated palsies, but recovery is usually complete. Vasculitis within the orbital apex (orbital apex syndrome) or brainstem dysfunction is postulated to be the cause of cranial nerve palsies. A vaccine of a lyophilized preparation of the oka strain of live, attenuated varicella-zoster virus is suggested for patients who are at risk of developing HZ and has been shown to boost immunity against HZ virus in older patients.

Infection in the elderly

Many functional, demographic, and immunologic changes associated with aging are responsible for increasing the incidence and severity of infectious diseases in the elderly. Management is complicated by age-related organ system changes. Because many of the elderly are on multiple medications for underlying illnesses, antimicrobial therapy needs to be chosen keeping drug interactions and adverse events in mind. Common infections seen in the elderly are infections of skin and soft tissue, urinary tract, respiratory tract, and gastrointestinal tract. Organized and well-funded programs to address infectious disease issues in the elderly are the only way to improve care.

Pharmacokinetics of acyclovir after intravenous infusion of acyclovir and after oral administration of acyclovir and its prodrug valacyclovir in healthy adult horses

The purpose of this study was twofold. The first aim was to evaluate the oral bioavailability and pharmacokinetics (PKs) of acyclovir in horses after intravenous (i.v.) administration and after oral administration of acyclovir and its prodrug, valacyclovir. Second, we aimed to combine these PK data with pharmacodynamic (PD) information, i.e., 50% effective concentrations (EC(50) values) from in vitro studies, to design an optimal dosage schedule. Three treatments were administered to healthy adult horses: 10 mg of acyclovir/kg of body weight delivered as an i.v. infusion over 1 h, 20 mg of acyclovir/kg administered as tablets by nasogastric intubation, and 20 mg of valacyclovir/kg administered as tablets by nasogastric intubation. Total plasma concentrations were measured by a high-performance liquid chromatography method combined with fluorescence detection, while unbound plasma concentrations were determined by liquid chromatography-tandem mass spectrometry. The peak concentration of i.v. acyclovir was approximately 10 mug/ml for both the total and the unbound plasma concentrations. The mean half-life of elimination was between 5.05 h (total concentration) and 11.9 h (unbound concentration). Oral administration of acyclovir resulted in low maximum concentration in plasma (C(max)) and poor bioavailability. A 10-times-higher C(max) and an 8-times-higher bioavailability were achieved with oral administration of valacyclovir. The i.v. administration of 10 mg/kg acyclovir and the oral administration of 20 mg/kg valacyclovir achieved concentrations within the sensitivity range of equine herpesvirus type 1 (EHV-1). The higher bioavailability of valacyclovir makes it an attractive candidate for the prophylactic and/or therapeutic treatment of horses infected with EHV-1. The results from the PK/PD modeling showed that a dosage of 40 mg/kg valacyclovir, administered three times daily, would be sufficient to reach plasma concentrations above the EC(50) values.

The change in zoster-associated pain treated with oral valaciclovir in immunocompetent patients with acute herpes zoster

We have analysed zoster-associated pain treated with valaciclovir (VCV) in immunocompetent patients with acute herpes zoster over 6 months, and evaluated the safety of VCV. We know of no reports that evaluate postherpetic neuralgia (PHN) treated with VCV for 6 months. Predisposing factors that influence PHN were age (over 60 years), clustered vesicles, severity of eruption, sleep disturbance, and hypesthesia. Timing of the administration of VCV before or after the onset of rash did not influence the incidence of PHN. No serious adverse reactions were observed during the administration of VCV.

Pulmonary complications of haematopoietic cell transplantation in children

Paediatric haematopoietic cell transplantation has experienced significant advances in the last few decades. However, pulmonary complications are an important limitation to the efficacy of this intervention, contributing to post-transplantation morbidity and mortality. Such complications persist even in experienced centres and occur in adult and paediatric recipients. This review identifies the paediatric pulmonary complications that are commonly seen following haematopoietic cell transplantation and addresses both infectious and non-infectious aetiologies and their clinical manifestations, evaluation, and potential therapy. Ultimately, improvement in outcomes will require attention to immunosuppression as well as traditional diagnostic procedures and treatment. This article aims to review the current state of pulmonary complications post-transplantation, to examine the impact of our recent advances and changes in treatment, and to identify potential future therapies and hypothesise what role these might have on long-term survival.

Herpes Zoster: Medical and Nursing Management

Herpes zoster, the latent descendent of the varicella zoster virus, commonly is seen in clinical practice. Healthcare providers must recognize and treat the virus to decrease the incidence of postherpetic neuralgic pain syndrome. Treatment with an antiviral medication regimen should be initiated rapidly for patients who have had lesions for up to 72 hours. Acyclovir has been the treatment of choice for herpes zoster in the past, but newer drugs, such as valacyclovir, a prodrug of acyclovir, and famciclovir, are as effective for treating the virus and have more convenient dosing regimens and decreased incidence of postherpetic neuralgia.

Validation of the genital herpes treatment satisfaction questionnaire (GHerpTSQ) in status and change versions

A new measure of treatment satisfaction (GHerpTSQ) for recurrent genital herpes simplex virus (HSV) was validated and used to evaluate two therapeutic strategies widely used for the management of HSV: episodic treatment, where individual herpes outbreaks are treated as they arise; suppressive therapy, where treatment is taken daily to prevent HSV outbreaks. Satisfaction with treatment is important since daily dosing with suppressive therapy is necessary in the absence of symptoms. A 12-item questionnaire was designed using a modified form of the Diabetes treatment satisfaction questionnaire (DTSQ). The psychometric properties of the GHerpTSQ were evaluated within a sample of 125 Canadians with a history of HSV (type 1, 2) infection participating in a 48 week randomised cross-over trial. Factor analysis suggested that the items can be analysed as two separate subscales corresponding to Control/effectiveness, and Convenience/lifestyle; the single item concerning side effects was retained for separate analysis. Forced one-factor analysis showed that the two subscales can be combined to obtain a total score relating to overall treatment satisfaction. The GHerpTSQ has good internal reliability, clear structure with little overlap of subscales and evidence of good sensitivity to changes in treatment.

Famciclovir

Famciclovir (Famvir) is the oral prodrug of penciclovir, an agent that has demonstrated antiviral activity against herpes simplex viruses, type 1 (HSV-1) and 2 (HSV-2) [which cause orolabial and/or genital herpes simplex], and against varicella zoster virus (VZV) [a reactivation of which leads to herpes zoster]. Famciclovir has efficacy similar to that of aciclovir (in immunocompetent or immunocompromised patients) or valaciclovir (in immunocompetent patients) in the treatment of herpes zoster, and efficacy similar to aciclovir in the treatment of first or recurrent episodes of genital herpes (in immunocompetent or immunocompromised patients). Famciclovir also has efficacy in the suppression of recurrent episodes of genital herpes, and in the treatment of orolabial herpes, in immunocompetent patients. As such, famciclovir is a well tolerated first-line option for the treatment of herpes zoster and the treatment and suppression of genital herpes, and is approved for the treatment of recurrent orolabial herpes. Convenient patient-initiated single-day (for recurrent genital herpes) and single-dose (for orolabial herpes) dosage regimens may contribute to treatment compliance, patient acceptability and subsequent treatment outcomes.

Hematopoietic stem cell transplantation: a primer for the primary care physician

Hematopoietic stem cell transplantation has been used for many years to treat various malignant and nonmalignant hematologic conditions. However, the high-dose conditioning regimen can lead to major organ dysfunction, life-threatening infection and bleeding. In the allogeneic setting, graft-versus-host disease may also develop, making post-transplant management complex. Once a transplant recipient is discharged from hospital and returns to his or her local community, the primary care physician can play an important role in care. Recipients of stem cell transplants may be severely immunocompromised for many months after transplantation, especially if they are still taking immunosuppressive drugs. Furthermore, endocrine and metabolic deficiencies can develop, and transplant survivors are at risk of a second malignant disease. This review is intended as a basic overview of allogeneic and autologous stem cell transplantation with a special focus on long-term follow-up issues relevant to primary care providers.

Factors influencing the features of postherpetic neuralgia and outcome when treated with tricyclics

This paper retrospectively reviews features of postherpetic neuralgia (PHN) in up to 279 personal patients in relation to treatment outcome when treated with tricyclic antidepressants (TCAs). Factors affecting characteristics of PHN: (i) Patients with allodynia (89%) and/or burning pain (56%) have a much higher visual analogue pain intensity score than those without; (ii) Acyclovir (ACV) given for acute shingles (HZ) does not reduce the incidence of subsequent PHN, but reduces the pain intensity in PHN patients with allodynia; (iii) ACV given for acute HZ reduces the incidence of burning pain in subsequent PHN, but not of allodynia; (iv) ACV given for acute HZ reduces the incidence of clinically detectable sensory deficit in subsequent PHN. Factors affecting outcome of TCA-treated PHN: (i) The point in time at which TCA treatment is commenced is by far the most critical factor: started between 3 and 12 months after acute HZ onset, more than two-thirds obtain pain relief (NNT=1.8); between 13 and 24 months, two-fifths (41%) (NNT=3.6); and more than two years, one-third (NNT=8.3). Background and paroxysmal pain disappear earlier and are more susceptible of relief than allodynia. (ii) Twice as many (86%) of PHN patients without allodynia obtain pain relief with TCA treatment than those with (42%); (iii) the use of ACV for acute HZ more than halves the time-to-relief of PHN patients by TCAs; (iv) PHN patients with burning pain are significantly less likely to obtain pain relief with TCAs than those without (p<0.0001).

Oral antivirals revisited in the treatment of herpes zoster: what do they accomplish?

Oral antiviral agents currently represent the most important therapeutic keystone in the treatment of herpes zoster. Three oral antiviral agents are available for the treatment of herpes zoster: acyclovir, its derivative valacyclovir, and famciclovir. Meta-analysis of published data has shown that oral acyclovir significantly reduces various herpes zoster-related symptoms as well as the duration, intensity and prevalence of zoster-associated pain (ZAP). However, this drug does not influence postherpetic neuralgia. The newer agents famciclovir and valacyclovir exhibit a better oral bioavailability than acyclovir. These agents have demonstrated similar efficacy to acyclovir with ZAP and they require less frequent administration. When initiated within 72 hours, oral antiviral therapy of herpes zoster is beneficial in selected, elderly immunocompetent patients, reducing the duration and intensity of ZAP and providing more rapid skin lesion healing. Oral antivirals are also of benefit in immunocompromised patients with uncomplicated herpes zoster. However, signs of cutaneous and visceral dissemination should be monitored; if signs occur, intravenous antiviral therapy is indicated.

Patients' preference of valacyclovir once-daily suppressive therapy versus twice-daily episodic therapy for recurrent genital herpes: a randomized study

BACKGROUND

Valacyclovir is effective for suppressive and episodic treatment of recurrent genital herpes. Few data on patients' treatment strategy preferences are available.

GOAL

The goal was to assess patients' preference, satisfaction, and quality of life with suppressive versus episodic treatment of recurrent genital herpes.

STUDY DESIGN

This was a multicenter, open-label, randomized, two-arm, crossover 48-week study involving 225 patients with genital herpes.

RESULTS

Suppressive valacyclovir therapy was preferred to episodic valacyclovir treatment by 72% of patients (P < 0.001). Overall treatment satisfaction and quality of life were significantly greater during suppressive therapy (P < 0.001 and P = 0.002, respectively). The risk of recurrence during the first 24 weeks was reduced by 78% with suppressive therapy (P < 0.001). Significantly fewer patients experienced recurrences during suppressive treatment than with episodic treatment (P < 0.001). Valacyclovir was well tolerated.

CONCLUSIONS

Suppressive valacyclovir was preferred to episodic therapy by most patients. Suppressive therapy was associated with increased treatment satisfaction, and decreased risk and lower frequency of recurrences.

Ocular penetration of acyclovir and its peptide prodrugs valacyclovir and val-valacyclovir following systemic administration in rabbits: An evaluation using ocular microdialysis and LC-MS

PURPOSE

To investigate the ocular penetration of acyclovir and its prodrugs following systemic administration and to elucidate the mechanism of penetration.

METHODS

Hydrophilic peptide prodrugs of acyclovir were infused intravenously in New Zealand albino rabbits over 45 min at a dose equivalent to 30 mmoles/kg acyclovir. Aqueous and vitreous humor samples were obtained utilizing ocular microdialysis and blood samples were obtained from the mid ear vein using a cannula.

RESULTS

The plasma bioavailability for acyclovir, valacyclovir and val-valacyclovir were similar with area under curve values being 896.24 (+/-143.58), 776.54 (+/-197.52), 824.69 (+/-217.43) min x micromoles/L respectively. Anterior segment area under curve values were 53.70 (+/-35.58), 139.85 (+/-9.43) and 291.05 (+/-88.13) min x micromoles/L respectively while the mean residence time values were 46.47 (+/-24.94), 76.30 (+/-7.24) and 188.39 (+/-80.73) min respectively. Vitreous levels of the prodrugs were not measurable.

CONCLUSIONS

The valine and valine-valine ester prodrugs of ACV penetrated the anterior segment of the eye much better than acyclovir alone, probably via a carrier mediated transport mechanism.

Prophylaxis of herpesvirus infections in immunocompetent and immunocompromised older patients

In older patients, prophylaxis of herpesvirus infections mainly involves preventing the recurrence of herpes simplex virus (HSV) and complications of herpes zoster in immunocompetent patients, while in immunocompromised patients it is more concerned with the prevention of opportunistic virus reactivation. HSV ocular infection is the most frequent cause of corneal blindness in the US. The effectiveness of aciclovir 400mg twice daily in preventing the recurrence of HSV eye disease in immunocompetent patients has been well demonstrated. The issue of treatment duration for patients with highly recurrent ocular herpes remains unresolved. Post-herpetic neuralgia (PHN) is one of the most common neuralgic illnesses worldwide. Some progress in prevention of PHN has been made with a combination of antiviral therapy (famciclovir or valaciclovir), started within 72 hours of onset of the rash, and analgesic treatment. However, the best prevention of PHN is the prevention of herpes zoster disease, and the varicella vaccine is an option which over the next few years will be tested in clinical trials. For immunocompromised patients of any age, restoring immunity prevents herpesvirus disease, as demonstrated for cytomegalovirus (CMV) in AIDS patients receiving highly active antiretroviral therapy. Specific antiviral therapy during the initial period after transplantation could prevent reactivation of HSV or CMV in seropositive recipients. Whether pre-emptive therapy or prophylaxis with ganciclovir is the optimal approach against CMV remains controversial, and the relative merits and limitations of each approach may guide the choice. In stem cell transplantation, pre-emptive therapy with foscarnet avoids the neutropenia and related complications associated with ganciclovir. In renal transplant recipients, universal prophylaxis of CMV infection with valaciclovir has the same efficacy as ganciclovir. Although it is relatively toxic, cidofovir should be further evaluated because of its in vitro activity against most DNA viruses.

Development and validation of a plasma assay for acyclovir using high-performance capillary electrophoresis with sample stacking

A sensitive plasma assay for acyclovir has been developed and validated. Acyclovir was separated from plasma components using Oasis HLB columns. Separation was obtained with no plasma interference using micellar electrokinetic chromatography (175 mM SDS) and hydroxypropyl-beta-cyclodextrin (100 mM) in 90 mM borate buffer (pH 8.8) containing 0.2% NaCl. High sensitivity was achieved by large volume sample introduction and stacking. The linear range was from 20 to 10000 ng/ml with a limit of quantitation of 20 ng/ml. This method is a viable alternative to HPLC because of its high separation and sensitivity, reproducibility, and adaptability to other nucleoside analogs.

Separation methods for acyclovir and related antiviral compounds

Acyclovir (ACV) is an antiviral drug, which selectively inhibits replication of members of the herpes group of DNA viruses with low cell toxicity. Valaciclovir (VACV), a prodrug of ACV is usually preferred in the oral treatment of viral infections, mainly herpes simplex virus (HSV). Also other analogues such as ganciclovir and penciclovir are discussed here. The former acts against cytomegalovirus (CMV) in general and the latter against CMV retinitis. The action mechanism of these antiviral drugs is presented briefly here, mainly via phosphorylation and inhibition of the viral DNA polymerase. The therapeutic use and the pharmacokinetics are also outlined. The measurement of the concentration of acyclovir and related compounds in biological samples poses a particularly significant challenge because these drugs tend to be structurally similar to endogenous substances. The analysis requires the use of highly selective analytical techniques and chromatography methods are a first choice to determine drug content in pharmaceuticals and to measure them in body fluids. Chromatography can be considered the procedure of choice for the bio-analysis of this class of antiviral compounds, as this methodology is characterised by good specificity and accuracy and it is particularly useful when metabolites need to be monitored. Among chromatographic techniques, the reversed-phase (RP) HPLC is widely used for the analysis. C18 Silica columns from 7.5 to 30 cm in length are used, the separation is carried out mainly at room temperature and less than 10 min is sufficient for the analysis at 1.0-1.5 ml/min of flow-rate. The separation methods require an isocratic system, and various authors have proposed a variety of mobile phases. The detection requires absorbance or fluorescence measurements carried out at 250-254 nm and at lambdaex=260-285 nm, lambdaem=375-380 nm, respectively. The detection limit is about 0.3-10 ng/ml but the most important aspect is related to the sample treatment, mainly when body fluids are under examination. The plasma samples obtained from human blood are pre-treated with an acid or acetonitrile deproteinization and the supernatant after centrifugation is successively extracted before RP-HPLC injection. Capillary Electrophoresis methods are also discussed. This new analytical approach might be the expected evolution, in fact the analyses are improved with regard to time and performance, in particular coated capillary as well as addition of stabilisers have been employed. The time of analysis is shortened arriving at less than half a minute. Furthermore by using an electrochemical detection, and having a calibration linearity in the range of 0.2-20.0 ng/ml, the detection limit is 0.15 microg/ml. The measurements of acyclovir and penciclovir have been presented but in the future other related drugs will probably be available using CE methods.