Oseltamivir in seasonal influenza: cumulative experience in low- and high-risk patients

Antiviral options and therapeutics against influenza: history, latest developments and future prospects

Drugs and chemotherapeutics have helped to manage devastating impacts of infectious diseases since the concept of 'magic bullet'. The World Health Organization estimates about 650,000 deaths due to respiratory diseases linked to seasonal influenza each year. Pandemic influenza, on the other hand, is the most feared health disaster and probably would have greater and immediate impact on humanity than climate change. While countermeasures, biosecurity and vaccination remain the most effective preventive strategies against this highly infectious and communicable disease, antivirals are nonetheless essential to mitigate clinical manifestations following infection and to reduce devastating complications and mortality. Continuous emergence of the novel strains of rapidly evolving influenza viruses, some of which are intractable, require new approaches towards influenza chemotherapeutics including optimization of existing anti-infectives and search for novel therapies. Effective management of influenza infections depend on the safety and efficacy of selected anti-infective in-vitro studies and their clinical applications. The outcomes of therapies are also dependent on understanding diversity in patient groups, co-morbidities, co-infections and combination therapies. In this extensive review, we have discussed the challenges of influenza epidemics and pandemics and discoursed the options for anti-viral chemotherapies for effective management of influenza virus infections.

The novel immunobiotic Clostridium butyricum S-45-5 displays broad-spectrum antiviral activity in vitro and in vivo by inducing immune modulation

Clostridium butyricum is known as a probiotic butyric acid bacterium that can improve the intestinal environment. In this study, we isolated a new strain of C. butyricum from infant feces and evaluated its physiological characteristics and antiviral efficacy by modulating the innate immune responses in vitro and in vivo. The isolated C. butyricum S-45-5 showed typical characteristics of C. butyricum including bile acid resistance, antibacterial ability, and growth promotion of various lactic acid bacteria. As an antiviral effect, C. butyricum S-45-5 markedly reduced the replication of influenza A virus (PR8), Newcastle Disease Virus (NDV), and Herpes Simplex Virus (HSV) in RAW264.7 cells in vitro. This suppression can be explained by the induction of antiviral state in cells by the induction of antiviral, IFN-related genes and secretion of IFNs and pro-inflammatory cytokines. In vivo, oral administration of C. butyricum S-45-5 exhibited prophylactic effects on BALB/c mice against fatal doses of highly pathogenic mouse-adapted influenza A subtypes (H1N1, H3N2, and H9N2). Before challenge with influenza virus, C. butyricum S-45-5-treated BALB/c mice showed increased levels of IFN-β, IFN-γ, IL-6, and IL-12 in serum, the small intestine, and bronchoalveolar lavage fluid (BALF), which correlated with observed prophylactic effects. Interestingly, after challenge with influenza virus, C. butyricum S-45-5-treated BALB/c mice showed reduced levels of pro-inflammatory cytokines and relatively higher levels of anti-inflammatory cytokines at day 7 post-infection. Taken together, these findings suggest that C. butyricum S-45-5 plays an antiviral role in vitro and in vivo by inducing an antiviral state and affects immune modulation to alleviate local and systemic inflammatory responses caused by influenza virus infection. Our study provides the beneficial effects of the new C. butyricum S-45-5 with antiviral effects as a probiotic.

A Review on the Potential Species of the Zingiberaceae Family with Anti-viral Efficacy Towards Enveloped Viruses

Natural products are a great wellspring of biodiversity for finding novel antivirals, exposing new interactions between structure and operation and creating successful defensive or remedial methodologies against viral diseases. The members of Zingiberaceae traditional plant and herbal products have robust anti-viral action, and their findings will further lead to the production of derivatives and therapeutic. Additionally, it highlights the insight of utilizing these phytoextracts or their constituent compounds as an emergency prophylactic medicine during the pandemic or endemic situations for novel viruses. In this connection, this review investigates the potential candidates of the Zingiberaceae family, consisting of bioactive phytocompounds with proven antiviral efficacy against enveloped viruses. The present study was based on published antiviral efficacy of Curcuma longa, Zingiber officinale, Kaempferia parviflora, Aframomum melegueta Elettaria cardamomum, Alpina Sps (belongs to the Zingiberaceae family) towards the enveloped viruses. The relevant data was searched in Scopus”, “Scifinder”, “Springer”, “Pubmed”, “Google scholar” “Wiley”, “Web of Science”, “Cochrane “Library”, “Embase”, Dissertations, theses, books, and technical reports. Meticulously articles were screened with the subject relevancy and categorized for their ethnopharmacological significance with in-depth analysis. We have comprehensively elucidated the antiviral potency of phytoextracts, major composition, key compounds, mode of action, molecular evidence, immunological relevance, and potential bioactive phytocompounds of these five species belonging to the Zingiberaceae family. Conveniently, these phytoextracts exhibited multimode activity in combating the dreadful enveloped viruses.

A brief review of influenza virus infection

Influenza is an acute viral respiratory infection that affects all age groups and is associated with high mortality during pandemics, epidemics, and sporadic outbreaks. Nearly 10% of the world's population is affected by influenza annually, with about half a million deaths each year. Influenza vaccination is the most effective method for preventing influenza infection and its complications. The influenza vaccine's efficacy varies each season based on the circulating influenza strains and vaccine uptake rates. Currently, three antiviral drugs targeting the influenza virus surface glycoprotein neuraminidase are available for treatment and prophylaxis of disease. Given the significant burden of influenza infection globally, this review is focused on the latest findings in the etiology, epidemiology, transmission, clinical manifestation, diagnosis, prevention, and treatment of influenza.

Rate of use and effectiveness of oseltamivir in the treatment of influenza illness in high-risk populations: A systematic review and meta-analysis

BACKGROUND

Oseltamivir is recommended in the treatment of influenza illness in high-risk populations, including those with chronic heart and lung diseases.

OBJECTIVES

We conducted a systematic review and meta-analysis to determine the rate of use and effectiveness of oseltamivir in these groups of patients.

METHODS

The protocol for the systematic review was registered on PROSPERO (CRD42019125998). Medline, EMBASE, Cochrane CENTRAL, and CINAHL were searched for observational studies and randomized controlled trials published up to 16 February 2020. Quality appraisal of final studies was conducted using GRADE guidelines. Data were extracted using a predeveloped template. Main outcomes measured included the rate of use of oseltamivir for influenza-like-illness and its effectiveness in reducing disease severity in patients with cardiopulmonary diseases. Outcomes measured for effectiveness were influenza-related complications (respiratory infections and asthma exacerbations), hospitalization rates, and time to freedom from illness. Risk of bias was assessed using Cochrane's Risk of Bias 2.0 tool for randomized trials and Cochrane's Risk of Bias in nonrandomized Studies of Interventions tool for nonrandomized trials. Where data were available, pooled analyses were conducted. Dichotomous variables were evaluated using the Mantel-Hansel method. A random effect model was applied. Summary measures were reported as risk ratios where relevant.

RESULTS

Our systematic review identified nine studies. Oseltamivir use ranged from 25% to 100%. When oseltamivir group was compared to placebo, rates of respiratory tract infections reduced by 28% (RR = 0.72, 95% CI = 0.59-0.90), hospitalization reduced by 52% (RR = 0.48, 95% CI = 0.28-0.80) and median time to illness alleviation decreased by 10.4 to 120 hours. There was no significant reduction in asthma exacerbation rates.

CONCLUSIONS

Our systematic review suggests that the use of oseltamivir is beneficial in reducing disease severity, however, its use in high-risk population remains suboptimal.

Efficacy of oseltamivir compared with zanamivir in COPD patients with seasonal influenza virus infection: a randomized controlled trial

Influenza viruses exacerbate chronic obstructive pulmonary disease (COPD) with considerable morbidity and mortality. Zanamivir and oseltamivir are effective in treating influenza. However, their efficacy in relieving influenza symptoms in COPD patients remains unknown, with the lack of controlled trials in this subject. Therefore, we conducted this randomized controlled trial to investigate the clinical efficacy of both interventions in this population. Patients were allocated to two groups (80 patients each): oseltamivir (OSELTA) and zanamivir (ZANA) groups. Oseltamivir (75 mg) was orally administered twice daily for 5 days, while zanamivir (10 mg) was inhaled twice daily for 5 days. Clinical parameters including body temperature, influenza symptoms (i.e., sore throat, cough, etc.), and serial blood tests were recorded on days 1, 3, and 7. We analyzed primary (changes in body temperature) and secondary outcomes (changes in non-specific symptoms) using the pre-protocol and intention-to-treat analyses. Differences between groups were assessed using t-test. Oseltamivir and zanamivir significantly reduced body temperature on the 3rd day after treatment; however, the number of patients who reported clinical improvement in influenza-like symptoms was significantly higher in the OSELTA group compared to the ZANA group on days 3 (85 vs 68.8%, P=0.015) and 7 (97.5 vs 83.8%, P=0.003). However, no significant changes in hematological (white blood cells and its subtypes) and inflammatory (C-reactive protein) parameters were noted (P>0.05). Our results suggested that oseltamivir and zanamivir are effective in reducing body temperature, while oseltamivir led to better clinical improvement regarding influenza-like symptoms in patients with COPD.

Influenza-Mediated Lung Infection Models

Laboratory rodent influenza infection models have been and continue to be a critical tool for understanding virus-host interactions during infection. The incidence of seasonal influenza infections coupled with the need for novel therapeutics and universal vaccines highlights the need to uncover novel mechanisms of pathogenesis and protection. Mouse models are extremely useful for the evaluation of influenza vaccines and provide an invaluable tool to probe the immune response. This chapter describes the technique of intranasal inoculation of male C57BL/6J mice with an H1N1 strain of influenza (A/Puerto Rico/8/1934) and methods for assessing the optimum dose for infection, viral titers in lung tissue, and severity of disease.

Influenza burden, prevention, and treatment in asthma-A scoping review by the EAACI Influenza in asthma task force

To address uncertainties in the prevention and management of influenza in people with asthma, we performed a scoping review of the published literature on influenza burden; current vaccine recommendations; vaccination coverage; immunogenicity, efficacy, effectiveness, and safety of influenza vaccines; and the benefits of antiviral drugs in people with asthma. We found significant variation in the reported rates of influenza detection in individuals with acute asthma exacerbations making it unclear to what degree influenza causes exacerbations of underlying asthma. The strongest evidence of an association was seen in studies of children. Countries in the European Union currently recommend influenza vaccination of adults with asthma; however, coverage varied between regions. Coverage was lower among children with asthma. Limited data suggest that good seroprotection and seroconversion can be achieved in both children and adults with asthma and that vaccination confers a degree of protection against influenza illness and asthma-related morbidity to children with asthma. There were insufficient data to determine efficacy in adults. Overall, influenza vaccines appeared to be safe for people with asthma. We identify knowledge gaps and make recommendations on future research needs in relation to influenza in patients with asthma.

A pharmacologically immunosuppressed mouse model for assessing influenza B virus pathogenicity and oseltamivir treatment

Immunocompromised patients are highly susceptible to influenza virus infections. Although neuraminidase inhibitor (NAI) therapy has proved effective in these patients, the treatment regimens require optimization, which can be partly addressed via animal models. Here, we describe a pharmacologically immunosuppressed mouse model for studying the pathogenesis of influenza B viruses and evaluating the efficacy of antiviral treatment. We modeled clinical regimens for dexamethasone and cyclophosphamide to immunosuppress BALB/c mice that were then inoculated with B/Phuket/3073/2013 (Yamagata lineage) or B/Brisbane/60/2008 (BR/08, Victoria lineage) virus. Although both viruses caused morbidity and mortality in immunosuppressed mice, BR/08 was more virulent, consistently inducing greater morbidity and 100% lethality in mice inoculated with at least 10³ TCID₅₀/mouse. The replication of both viruses was prolonged in the lungs of immunosuppressed mice, but the extent of pulmonary inflammation in these mice was markedly less than that in immunocompetent animals. Most of the examined cytokines, including IFN-γ, IL-1β, and RANTES, were significantly decreased in the lungs of immunosuppressed mice, as compared to immunocompetent animals, until at least 10 days post-infection. Treatment with the NAI oseltamivir for 8 or 16 days increased the mean survival time and reduced virus spread in the lungs of immunosuppressed mice challenged with a lethal dose of BR/08 but did not completely provide protection or decrease the virus titers. Our data suggests that the synergy of the viral load and aberrant immune responses is a key contributor to the severity of infection, as well as the limited efficacy of oseltamivir, which in immunosuppressed mice curtails virus release without clearing infected cells.

Efficacy and Safety of Intravenous Peramivir Compared With Oseltamivir in High-Risk Patients Infected With Influenza A and B Viruses: A Multicenter Randomized Controlled Study

BACKGROUND

Clinical studies comparing the different neuraminidase inhibitors for treatment of at-risk patients with influenza have not been performed. To optimize such treatments, we assessed the efficacy and safety of intravenous peramivir compared with oral oseltamivir in treating seasonal influenza A or B virus infection.

METHODS

A multicenter, randomized, controlled clinical trial was conducted from December 2012 to May 2014 in high-risk patients infected with seasonal influenza. A total of 92 adult inpatients and outpatients with high risk factors (HRFs) were treated by either a single intravenous infusion of peramivir (600 mg) or oral administration of oseltamivir (75 mg, twice per day for 5 days).

RESULTS

The median times to clinical stability (time to reach <37°C) were 40.0 hours (95% confidence interval [CI] = 23.3-64.5) and 37.8 hours (95% CI = 26.3-45.3) in the peramivir and oseltamivir groups, respectively; these values did not reveal a significant difference. The virus titer and change of mean total symptom scores decreased similarly with both treatments. Results of step-wise regression suggested that virus type was a significantly effective prognostic factor with respect to illness resolution. Adverse events (AEs) with peramivir and oseltamivir occurred in 2.2% (n = 1/46) and 13.0% (n = 6/46) of patients, respectively. The severity of AEs was mild in all cases except 2 patients who showed pneumonia or COPD aggravation; both were in the oseltamivir group.

CONCLUSIONS

Intravenous peramivir was effective based on the result of direct comparison with oral oseltamivir. Thus our data show that peramivir is a useful option for the treatment of influenza-infected patients with HRFs.

Reduction of Neuraminidase Activity Exacerbates Disease in 2009 Pandemic Influenza Virus-Infected Mice

During the first wave of the 2009 pandemic, caused by a H1N1 influenza virus (pH1N1) of swine origin, antivirals were the only form of therapeutic available to control the proliferation of disease until the conventional strain-matched vaccine was produced. Oseltamivir is an antiviral that inhibits the sialidase activity of the viral neuraminidase (NA) protein and was shown to be effective against pH1N1 viruses in ferrets. Furthermore, it was used in humans to treat infections during the pandemic and is still used for current infections without reported complication or exacerbation of illness. However, in an evaluation of the effectiveness of oseltamivir against pH1N1 infection, we unexpectedly observed an exacerbation of disease in virus-infected mice treated with oseltamivir, transforming an otherwise mild illness into one with high morbidity and mortality. In contrast, an identical treatment regime alleviated all signs of illness in mice infected with the pathogenic mouse-adapted virus A/WSN/33 (H1N1). The worsened clinical outcome with pH1N1 viruses occurred over a range of oseltamivir doses and treatment schedules and was directly linked to a reduction in NA enzymatic activity. Our results suggest that the suppression of NA activity with antivirals may exacerbate disease in a host-dependent manner by increasing replicative fitness in viruses that are not optimally adapted for replication in that host.

IMPORTANCE

Here, we report that treatment of pH1N1-infected mice with oseltamivir enhanced disease progression, transforming a mild illness into a lethal infection. This raises a potential pitfall of using the mouse model for evaluation of the therapeutic efficacy of neuraminidase inhibitors. We show that antiviral efficacy determined in a single animal species may not represent treatment in humans and that caution should be used when interpreting the outcome. Furthermore, increased virulence due to oseltamivir treatment was the effect of a shift in the hemagglutinin (HA) and neuraminidase (NA) activity balance. This is the first study that has demonstrated that altering the HA/NA activity balance by reduction in NA activity can result in an increase in virulence in any animal model from nonpathogenic to lethal and the first to demonstrate a situation in which treatment with a NA activity inhibitor has an effect opposite to the intended therapeutic effect of ameliorating the infection.

Reducing the impact of influenza-associated secondary pneumococcal infections

When administered prophylactically, we show that the Toll-like receptor-2 (TLR-2) agonist PEG-Pam2Cys (pegylated-S-(2,3-bis(palmitoyloxy)propyl)cysteine) not only mediates potent anti-viral activity against influenza virus but also reduces the impact of secondary infections with Streptococcus pneumoniae (the pneumococcus) by reducing (i) pulmonary viral and bacterial burdens, (ii) the levels of proinflammatory cytokines that normally accompany influenza and S. pneumoniae secondary infections and (iii) the vascular permeability of the pulmonary tract that can allow bacterial invasion of the blood in mice. We also show that an inactivated detergent-disrupted influenza virus vaccine formulated with the Pam2Cys-based adjuvant R4-Pam2Cys provides the host with both immediate and long-term protection against secondary pneumococcal infections following influenza virus infection through innate and specific immune mechanisms, respectively. Vaccinated animals generated influenza virus-specific immune responses that provided the host with long-term protection against influenza virus and its sequelae. This vaccine, which generates an immediate response, provides an additional countermeasure, which is ideal for use even in the midst of an influenza outbreak.

Physiologically based pharmacokinetic modeling of impaired carboxylesterase-1 activity: effects on oseltamivir disposition

BACKGROUND AND OBJECTIVE

Human carboxylesterase-1 (CES1) is an enzyme that is primarily expressed in the liver, where it plays an important role in the metabolism of many commonly used medications. Ethanol (alcohol)-mediated inhibition of CES1 and loss-of-function polymorphisms in the CES1 gene can markedly reduce this enzyme's function. Such alterations in CES1 activity may have important effects on the disposition of substrate drugs. The aim of this study is to develop a physiologically based pharmacokinetic (PBPK) model to predict changes in CES1 substrate drug exposure in humans with CES1 activity impaired by ethanol or loss-of-function CES1 genetic polymorphisms.

METHODS

The antiviral drug oseltamivir, an ethyl ester prodrug that is rapidly converted in vivo to the active metabolite oseltamivir carboxylate (OSC) by CES1 was used as a probe drug for CES1 activity. Oseltamivir PBPK models integrating in vitro and in vivo data were developed and refined. Then the changes in oseltamivir and OSC exposure in humans with CES1 impaired by ethanol or polymorphisms were simulated using a PBPK model incorporating in vitro inhibition and enzyme kinetic data. Model assumptions were verified by comparison of simulations with observed and published data. A sensitivity analysis was performed to gain a mechanistic understanding of the exposure changes of oseltamivir and OSC.

RESULTS

The simulated changes in oseltamivir and OSC exposures in humans with CES1 impaired by ethanol or polymorphism were similar to the observed data. The observed exposures to oseltamivir were increased by 46 and 37 % for the area under the plasma concentration-time curve from time zero to 6 h (AUC6) and from time zero to 24 h (AUC24), respectively, with co-administration of ethanol 0.6 g/kg. In contrast, only a slight change was observed in OSC exposure. The simulated data show the same trend as evidenced by greater change in exposures to oseltamivir (27 and 26 % for AUC(6) and AUC(24), [corrected] respectively) than OSC (≤6 %).

CONCLUSIONS

The PBPK model of impaired CES1 activity correctly predicts observed human data. This model can be extended to predict the effects of drug interactions and other factors affecting the pharmacokinetics of other CES1 substrate drugs.

[Factors related to death by the Pandemic Influenza A (H1N1) 2009 in patients treated with oseltamivir]

This study aimed to identify factors related to death in Pandemic Influenza A(H1N1)2009 in patients treated with Oseltamivir. It is an observational and retrospective study, carried out with data of patients who had presented laboratorial diagnosis of the illness. Data were collected from the notification forms of the disease, belonging to a database of the Ministry of Health. Statistical analysis was performed by chi-square, Student t test and logistic regression, considering significant p values <0,05. The highest mortality was observed in patients aged between 20 and 59 years, low schooling, with the presence of comorbidities, not vaccinated, treated late and had more severe symptoms of infection. The identification of risk factors for death reinforces the need for prevention and early care, especially in the presence of factors that increase the clinical severity of disease.

Tracking oseltamivir-resistance in New Zealand influenza viruses during a medicine reclassification in 2007, a resistant-virus importation in 2008 and the 2009 pandemic

INTRODUCTION

Oseltamivir (Tamiflu®) is an important pharmaceutical intervention against the influenza virus. The importance of surveillance for resistance to oseltamivir has been highlighted by two global events: the emergence of an oseltamivir-resistant seasonal influenza A(H1N1) virus in 2008, and emergence of the influenza A(H1N1)pdm09 virus in 2009. Oseltamivir is a prescription medicine in New Zealand, but more timely access has been provided since 2007 by allowing pharmacies to directly dispense oseltamivir to patients with influenza-like illness.

OBJECTIVE

To determine the frequency of oseltamivir-resistance in the context of a medicine reclassification in 2007, the importation of an oseltamivir-resistant seasonal influenza virus in 2008, and the emergence of a pandemic in 2009.

METHODS

A total of 1795 influenza viruses were tested for oseltamivir-resistance using a fluorometric neuraminidase inhibition assay. Viruses were collected as part of a sentinel influenza surveillance programme between the years 2006 and 2010.

RESULTS

All influenza B, influenza A(H3N2) and influenza A(H1N1)pdm09 viruses tested between 2006 and 2010 were shown to be sensitive to oseltamivir. Seasonal influenza A(H1N1) viruses from 2008 and 2009 were resistant to oseltamivir. Sequencing of the neuraminidase gene showed that the resistant viruses contained an H275Y mutation, and S247N was also identified in the neuraminidase gene of one seasonal influenza A(H1N1) virus that exhibited enhanced resistance.

DISCUSSION

No evidence was found to suggest that increased access to oseltamivir has promoted resistance. A probable importation event was documented for the global 2008 oseltamivir-resistant seasonal A(H1N1) virus nine months after it was first reported in Europe in January 2008.

Neuraminidase inhibitors for influenza: a review and public health perspective in the aftermath of the 2009 pandemic

OBJECTIVES

The objectives of this study were to: (1) reflect on key stages in the discovery, development and pre-pandemic use of neuraminidase inhibitors (NAIs), (2) summarise the evidence of NAI effectiveness for treatment and prophylaxis of seasonal influenza prior to the 2009 pandemic, and (3) summarise the evidence base generated during the 2009 pandemic period.

DESIGN

A rapid systematic review of evidence published to June 2010 was conducted where existing high-quality systematic reviews formed a baseline and were supplemented with data from other reviews, randomised controlled trials (RCTs) and observational studies.

MAIN OUTCOME MEASURES

Severity and duration of symptoms; rates of severe illness, complications and death following treatment for influenza or influenza-like illness; rates of influenza and influenza-like illness following long-term prophylaxis or post-exposure prophylaxis of household contacts.

RESULTS

Prior to the 2009 pandemic, evidence from RCTs conducted in seasonal influenza epidemics indicated that NAIs used to treat laboratory-confirmed influenza in healthy adults reduced the duration of illness by one day. NAIs provide high levels of protective efficacy in adults when given long-term or in household-based post-exposure prophylaxis for seasonal influenza. Several 2009 pandemic period observational studies suggest that early treatment may reduce rates of hospitalisation and in-hospital mortality, but data from that period do not substantially increase the evidence base on prophylaxis, although they confirm effectiveness.

CONCLUSIONS

NAIs should be deployed during a future pandemic for either post-exposure prophylaxis or treatment depending on national policy considerations and logistics. The existing evidence base on effectiveness against severe outcomes requires supplementation.

The value of neuraminidase inhibitors for the prevention and treatment of seasonal influenza: a systematic review of systematic reviews

Controversy has arisen regarding the effectiveness of neuraminidase inhibitors (NIs), especially against influenza-related complications. A literature search was performed to critically assess the evidence collected by the available systematic reviews (SRs) regarding the benefits and disadvantages of NIs (oseltamivir, zanamivir) compared to placebos in healthy and at-risk individuals of all ages for prophylaxis and treatment of seasonal influenza. A SR was done using the Cochrane Database of Systematic Reviews, Health Technology Assessment Database, Database of Abstracts of Reviews of Effects, and Medline (January 2006-July 2012). Two reviewers selected SRs based on randomized clinical trials, which were restricted to intention-to-treat results, and they assessed review (AMSTAR) and study quality indicators (GRADE). The SRs included (N = 9) were of high quality. The efficacy of NIs in prophylaxis ranged from 64% (16-85) to 92% (37-99); the absolute risk reduction ranged from 1.2% to 12.1% (GRADE moderate to low). Clinically relevant treatment benefits of NIs were small in healthy adults and children suffering from influenza-like illness (GRADE high to moderate). Oseltamivir reduced antibiotic usage in healthy adults according to one SR, but this was not confirmed by other reviews (GRADE low). Zanamivir showed a preventive effect on antibiotic usage in children (95% (77-99);GRADE moderate) and on the occurrence of bronchitis in at-risk individuals (59% (30-76);GRADE moderate). No evidence was available on the treatment benefits of NIs in elderly and at-risk groups and their effects on hospitalization and mortality. In oseltamivir trials, nausea, vomiting and diarrhea were significant side-effects. For zanamivir trials, no adverse effects have been reported. The combination of diagnostic uncertainty, the risk for virus strain resistance, possible side effects and financial cost outweigh the small benefits of oseltamivir or zanamivir for the prophylaxis and treatment of healthy individuals. No relevant benefits of these NIs on complications in at-risk individuals have been established.

Rianimazione e influenza grave: pandemia influenzale A (H1N1)

Durante la pandemia influenzale A (H1N1) nel 2009-2010, il 20% dei pazienti ospedalizzati ha presentato delle forme gravi con trasferimento in rianimazione. L’età mediana di questi pazienti era di circa 30 anni, con una percentuale leggermente inferiore al 10% di donne gravide. Si riscontrava circa un 80% di comorbilità, essenzialmente malattie cardiorespiratorie e obesità. Il tempo mediano tra la comparsa della sindrome influenzale e il trasferimento in rianimazione era di un giorno. I test di diagnosi rapida sono realizzabili a partire da semplici campioni respiratori, ma la loro sensibilità rimane bassa. La durata mediana del ricovero in rianimazione era dell’ordine di 11 giorni. Circa il 70% dei pazienti ha richiesto una ventilazione meccanica (durata mediana di dieci giorni). Oltre il 95% di questi pazienti ha ricevuto un trattamento antivirale e oltre il 95% degli antibiotici, a fronte di un 20% soltanto di infezioni batteriche documentate, soprattutto da Streptococcus pneumoniae e Staphylococcus aureus. La mortalità globale a 28 giorni era del 17%. Il tempo mediano tra la comparsa della sindrome influenzale e il decesso era di 14 giorni. Fra questi decessi, la maggior parte dei pazienti aveva ricevuto un trattamento antivirale, ma non sempre nelle prime 48 ore, il che appare un fattore prognostico infausto. Così, il trattamento antivirale è consigliato nelle forme gravi; il virus pandemico A (H1N1) era sensibile ai due inibitori della neuraminidasi. Sono stati riscontrati dei casi sporadici di resistenza, il che spinge a sviluppare altre molecole attive sui virus influenzali.

Oseltamivir pharmacokinetics in critically ill adults receiving extracorporeal membrane oxygenation support

Extracorporeal membrane oxygenation (ECMO) is known to affect pharmacokinetics and hence optimum dosing. The aim of this open label, prospective study was to investigate the pharmacokinetics of oseltamivir (prodrug) and oseltamivir carboxylate (active metabolite) during ECMO. Fourteen adult patients with suspected or confirmed H1N1 influenza were enrolled in the study. Oseltamivir 75 mg was enterally administered twice daily and blood samples for pharmacokinetic assessment were taken on day 1 and 5. A multi-compartmental model to describe the pharmacokinetics of oseltamivir and oseltamivir carboxylate was developed using a non-linear mixed effects modelling approach. The median (range) clearance of oseltamivir carboxylate was 15.8 (4.8-36.6) l/hour, lower than the reported mean value of 21.5 l/hour in healthy adults. The median (range) steady state volume of distribution of oseltamivir carboxylate was 179 (61-436) litres, much greater than healthy adults but similar to previous reports in critically ill patients. Substantial 'between subject' variability in systemic exposure to oseltamivir carboxylate was revealed; median (range) area under the curve and Cmax were 4346 (644-13660) ng/hour/ml and 509 (54-1277) ng/ml, respectively. Both area under the curve and Cmax were significantly correlated with serum creatinine (r2=0.37, P=0.02 and r2=0.29, P=0.02, respectively). Systemic exposure to oseltamivir carboxylate following the administration of enteral oseltamivir 75 mg twice daily in adult ECMO patients is comparable to those in ambulatory patients and far in excess of concentrations required to maximally inhibit neuraminidase activity of the H1N1 virus. Dosage adjustment for ECMO, per se, appears not to be necessary; however, doses should be reduced in patients with renal dysfunction.

Amaryllidaceae alkaloids inhibit nuclear-to-cytoplasmic export of ribonucleoprotein (RNP) complex of highly pathogenic avian influenza virus H5N1

Please cite this paper as: He et al. (2013) Amaryllidaceae alkaloids inhibit nuclear‐to‐cytoplasmic export of ribonucleoprotein (RNP) complex of highly pathogenic avian influenza virus H5N1. Influenza and Other Respiratory Viruses 7(6), 922–931.

Background  Few drugs are currently licensed to treat influenza A infection, and new therapies are needed, especially for highly pathogenic strains. Traditional medicinal plants, such as Lycoris radiata, are a potential source of new antiviral agents.

Objective  To test 15 Amaryllidaceae alkaloids isolated from the bulbs of L. radiata in vitro for antiviral activities against influenza virus type A, A/Chicken/GuangDong/178/2004 (H5N1, 178).

Methods  Antiviral activities of the compounds were tested in time‐of‐addition assays, hemagglutination inhibition (HI) assays, neuraminidase (NA) activity assays, and viral entry inhibition assays using H5N1‐HIV pseudoviruses. Effects of the compounds on localization and activity of the viral ribonucleoprotein (RNP) were determined by immunofluorescence and an RNP minigenome assay, respectively.

Results  Among the alkaloids, lycorine (AA1), hippeastrine (AA2), hemanthamine (AA3) and 11‐hydroxy vittatine (AA4) exhibited antiviral activities, with EC₉₀ values of 0·52, 82·07, 4·15, and 13·45 μm, respectively. These compounds did not affect the function of the outer membrane proteins or the viral entry process and viral RNP activity. As AA1 and AA3 exhibited stronger antiviral activities, they were further analyzed. Intracellular nucleoprotein (NP) localization showed that AA1 and AA3 inhibited the RNP complex in the nucleus at an early stage of a single‐round and multi‐round of replication.

Conclusion  Four Amaryllidaceae alkaloids were first determined that could exert anti‐influenza activities after virus entry into cells. Furthermore, AA1 and AA3 could inhibit nuclear‐to‐cytoplasmic export of the RNP complex of virus replication. Thus, these compounds may be developed further as anti‐influenza drug candidates.

Comparison of nasal and nasopharyngeal swabs for influenza detection in adults

OBJECTIVE

Examine differences in the detection of influenza by specimen and test type using paired nasal and nasopharyngeal swabs.

DESIGN

Prospective study

SETTING

Enrollment took place between January and March 2007 in a central Wisconsin population.

PARTICIPANTS

Adult patients were screened and enrolled by trained research coordinators following medical encounters for acute respiratory illnesses of <10 days duration.

METHODS

Paired nasal and nasopharyngeal swabs were collected from consenting patients and tested by both real-time reverse transcriptase polymerase chain reaction (rRT-PCR) and viral culture. A composite measure of positivity was used as the gold standard; cases included any positive result by rRT-PCR or viral culture from either specimen type.

RESULTS

Paired samples were collected from 240 adults; 33 (14%) individuals tested positive for influenza by rRT-PCR. Using rRT-PCR, the sensitivity of the nasal swab was 89% (95% CI, 78%-99%) and the sensitivity of the nasopharyngeal swab was 94% (95% CI, 87%-100%), compared to a composite gold standard.

CONCLUSION

Test sensitivity did not vary significantly by swab type when using a highly sensitive molecular diagnostic test, but power was limited to detect modest differences.

Simple and sensitive assay for quantification of oseltamivir and its active metabolite oseltamivir carboxylate in human plasma using high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry: improved applicability to pharmacokinetic study

Although liquid chromatography/electrospray ionization tandem mass spectrometry-based assays have been reported for the measurement of the antiviral oseltamivir (OS) in human samples, these assays either involve complicated sample pretreatment or lack sensitivity. Here we introduce a straightforward approach to improve the assay performance for OS and its metabolite oseltamivir carboxylate (OSC) in human plasma. A very low concentration of mobile phase modifier can improve the ionization efficiency of both analytes, thus enabling a high sensitivity without any matrix effect. The fast LC gradient further increases the sensitivity by narrowing the peak width (6-9s) and eluting the analytes at higher organic content. The increased ionization efficiency and minimized matrix effects enabled us to introduce a one-step protein precipitation for sample clean-up without compromising the sensitivity. The lower limit of quantification was 0.34 ng/mL for both analytes, which was at least 3 times more sensitive than published assays that involve complicated sample pretreatment. The assay involves measurement of analytes and their stable-isotope internal standards in small-volume (30-μL) plasma. Sodium fluoride was utilized to prevent the hydrolysis of OS during and after sampling. The calibration curve was linear over the range of 0.34-1000 ng/mL. Accuracy was 95-110% and the precision was 2.2-11.0%. This method was applied successfully to the human pharmacokinetic study of OS, and can estimate the relevant pharmacokinetic parameters of OS with more accuracy. The approach utilized in the optimization of assay performance can be extended to the measurement of other drugs in biomatrices.

Development of acute ischemic stroke in a patient with acute respiratory distress syndrome (ARDS) resulting from H1N1 pneumonia

Pneumonia due to H1N1 infection is now very common. We report a case of ischemic stroke which arose subsequently to H1N1 influenza. The patient was a female who developed acute respiratory distress syndrome (ARDS) after H1N1 influenza, was ventilated as per standard protocol and started treatment with oseltamivir. When sedation was stopped during weaning from the ventilator, she was found to have left hemiparesis resulting from multiple infarctions in the brain. Contrary to thrombocytosis usually seen in acute influenza, the platelet counts in our patient actually dropped. We suspected that increased interleukin release or stickiness of the platelets might have caused this ischemic stroke. In the course of time, she had acceptable neurological recovery following treatment with aspirin and neuro-rehabilitation. This case report provides evidence that a rare, debilitating complication like stroke can occur in H1N1 infection. A high index of suspicion of the probability of a cerebrovascular event should be borne in mind and regular neurological assessment should be done in such cases.

Absence of central nervous system and hypothermic effects after single oral administration of high doses of oseltamivir in the rat

Oseltamivir is widely used for the treatment and prophylaxis of influenza. Renewed interest in the central nervous system (CNS) tolerability profile of oseltamivir has been triggered by the reports of neuropsychiatric adverse events in patients with influenza. In addition, a recent pre-clinical study in rodents suggested a hypothermic effect of oseltamivir. The current studies investigated the CNS effects, body temperature effect and toxicokinetic profile of oseltamivir in rats. The CNS/temperature study included three groups receiving oseltamivir (500, 763 and 1000 mg/kg free base by oral gavage), one vehicle/control group and one reference group (D-amphetamine, 10 mg/kg). CNS parameters (behaviour, motor activity and co-ordination and sensory/motor reflex responses) and rectal temperature were measured at baseline and at five intervals until 8 hr after dosing. In the toxicokinetic study, rats received oseltamivir by oral gavage at 763 or 1000 mg/kg free base. Plasma, cerebrospinal fluid (CSF) and perfused brain concentrations of oseltamivir and its active metabolite, oseltamivir carboxylate (OC), were measured until 8 hr after dosing. Median scores for CNS parameters were similar in controls and animals receiving oseltamivir at all time points. Oseltamivir had no physiologically relevant effect on body temperature, but induced a short-lived and small dose-independent decrease in temperature in all active treatment groups at 1 hr after dosing only. Plasma concentrations of OC were higher than of oseltamivir, but the reverse was true in CSF and brain. CNS penetration was low for both moieties. In rats, oseltamivir at supratherapeutic doses up to 1000 mg/kg free base did not exert any effects on CNS function or hypothermic effects and led to limited CNS exposure, resulting in large safety margins.

Influenza pandêmica A (H1N1) 2009: fatores de risco para o internamento

OBJETIVO: Avaliar os aspectos da influenza pandêmica A (H1N1) 2009 em pacientes hospitalizados a fim de identificar os fatores de risco para o internamento e, consequentemente, para o agravamento da doença. MÉTODOS: Estudo observacional e retrospectivo realizado entre março e dezembro de 2010. Os dados foram coletados a partir do Sistema Nacional de Agravos de Notificação do Ministério da Saúde. Foram incluídos somente os pacientes hospitalizados e não hospitalizados com confirmação laboratorial da infecção durante o período de estudo. As variáveis referentes às características demográficas e clínicas foram avaliadas estatisticamente a fim de comparar as taxas de internamento na presença ou na ausência desses fatores. Os fatores de risco foram identificados por regressão logística. RESULTADOS: Foram incluídos no estudo 4.740 pacientes com confirmação laboratorial da infecção. Desses, 1.911 foram internados, e 258 (13,5%) foram a óbito. Os fatores de risco para o internamento foram idade (faixa etária de 20 a 29 anos), etnia negra ou indígena, presença de algumas comorbidades (cardiopatias, pneumopatias, nefropatias, hemoglobinopatia, imunodepressão, diabetes, obesidade, puerpério e tabagismo), número alto de comorbidades associadas, e alguns sintomas (dispneia, diarreia, vômito, dor torácica, hemoptise, pneumonia e sibilos). Níveis maiores de escolaridade e uso precoce do oseltamivir foram relacionados a fatores de proteção. A hospitalização contribuiu para o aumento da sobrevida. CONCLUSÕES: O conhecimento das características epidemiológicas que podem estar associadas a internação, gravidade da doença e mortalidade podem ser úteis na adoção de medidas preventivas e no diagnóstico e tratamento precoce da doença, colaborando para a diminuição dos óbitos e da necessidade de hospitalização.

Oseltamivir in seasonal, pandemic, and avian influenza: a comprehensive review of 10-years clinical experience

Oseltamivir (Tamiflu®; F. Hoffmann-La Roche Ltd, Basel, Switzerland) is an orally administered antiviral for the treatment and prevention of influenza A and B infections that is registered in more than 100 countries worldwide. More than 83 million patients have been exposed to the product since its introduction. Oseltamivir is recommended by the World Health Organization (WHO) for use in the clinical management of pandemic and seasonal influenza of varying severity, and as the primary antiviral agent for treatment of avian H5N1 influenza infection in humans. This article is a nonsystematic review of the experience gained from the first 10 years of using oseltamivir for influenza infections since its launch in early 2000, emphasizing recent advances in our understanding of the product and its clinical utility in five main areas. The article reviews the pharmacokinetics of oseltamivir and its active metabolite, oseltamivir carboxylate, including information on special populations such as children and elderly adults, and the co-administration of oseltamivir with other agents. This is followed by a summary of data on the effectiveness of oseltamivir treatment and prophylaxis in patients with all types of influenza, including pandemic (H1N1) 2009 and avian H5N1 influenza. The implications of changes in susceptibility of circulating influenza viruses to oseltamivir and other antiviral agents are also described, as is the emergence of antiviral resistance during and after the 2009 pandemic. The fourth main section deals with the safety profile of oseltamivir in standard and special patient populations, and reviews spontaneously reported adverse event data from the pandemic and pre-pandemic periods and the topical issue of neuropsychiatric adverse events. Finally, the article considers the pharmacoeconomics of oseltamivir in comparison with vaccination and usual care regimens, and as a component of pandemic influenza mitigation strategies.

Potential adverse effects of oseltamivir in rats: males are more vulnerable than females

Oseltamivir is the most widely used antiviral drug for the treatment and prophylaxis of influenza. However, not much is known about its adverse effects. The potential side effects were investigated in male and female rats (140-170 g). Oseltamivir was administered at 2.2 mg·kg(-1)·day(-1) for 5 days. For both genders, treatment with oseltamivir resulted in significant reductions in the hepatic activities of glutathione reductase, glutathione peroxidase, and glutathione S-transferase. Also for both genders, oseltamivir produced modest reductions in the hepatic activities of UDP-glucuronosyltransferase, quinone oxidoreductase, thioredoxin reductase, CYP1A1/2, and CYP3A, as well as hepatic glutathione content. For both genders, neither the kidney functions nor protein profile was affected by oseltamivir. Oseltamivir also caused significant elevation in serum levels of both triacylglycerols and LDL-cholesterol and in the activity of γ-glutamyl transpeptidase, in both genders. For male animals only, oseltamivir treatment elevated the serum level of total cholesterol as well as the activity of serum alanine aminotransferase, and reduced the hepatic activities of superoxide dismutase and catalase. Oseltamivir caused oxidative stress and acute toxicity in the liver, and disrupted the cholesterol and lipid metabolism but was less likely to cause serious drug interactions. There was a sexual differentiation in these adverse effects, with adverse effects being more evident in male rats.

Influenza in immunocompromised patients: considerations for therapy

Influenza infection results in substantial morbidity and mortality in immunocompromised patients, and the risks for influenza and its related complications depend on the degree of immunosuppression. In addition to influenza vaccination and infection control precautions, two classes of antiviral drugs are currently approved for treatment and prophylaxis in uncomplicated infected patients. However, there are no randomized controlled trials assessing the efficacy and safety of licensed antivirals for influenza management in immunocompromised patients. The purpose of this article is to highlight some considerations for therapy in immunocompromised patients, the usefulness of vaccination for the prevention of influenza and the clinical interest in surveillance of antiviral resistance.

Clinical manifestations, therapy and outcome of pandemic influenza a (H1N1) 2009 in hospitalized patients

Background/Aim. Increasing number of epidemiological and clinical studies to date showed that the pandemic influenza A (H1N1) 2009, by its characteristics, significantly differs from infection caused by seasonal influenza. Therefore, the information about clinical spectrum of manifestations, risk factors for severe form of the disease, treatment and outcome in patients with novel flu are still collected. Methods. A total of 98 patients (mean age 32 ? 15 years, range 14-88 years) with the signs and symptoms of novel influenza were treated in the Clinic for Infectious and Tropical Diseases, Military Medical Academy. There were 74 (75.5%) patients with suspected influenza A (H1N1) 2009, 10 (10.2%) with the likelihood and 14 (14.3%) with the confirmed influenza. In all the patients we registered the basic demographic data, risk factors for severe disease, symptoms and signs of influenza, laboratory tests and chest radiography. We analyzed antiviral therapy use and disease outcome (survived, died). Results. The average time from the beginning of influenza A (H1N1) to the admission in hospital was 3 days (0-16 days) and from the moment of hospitalization to the Intensive Care Unit (ICU) admission was 2 days (0-5 days). There were 49 (50.0%) patients, 20-29 years of age and 5 (5.1%) patients older than 65. A total of 21 (21.4%) patients were with underlying disease, 18 (18.4%) were obese, 19 (19.4%) were cigarette smokers. All of the patients had fever, 81 (82.6%) cough, while dyspnea and diarrhea were registered in ? of the patients. In more than 75% of the patients laboratory tests were within normal limits. The realtime polymerase chain reaction (PCR) test for identification of influenza A (H1N1) 2009 was positive in 14 (77.8%), while pneumonia was verified in 30 (30.7%) of the patients. Six (6.1%) patients, mean age of 45 ? 14 years (31-59 years) were admitted to the ICU, of whom five (5.1%) had Adult Respiratory Distress Syndrome (ARDS). Risk factors were registered more frequently in the patients with acute respiratory failure (14.2% vs 4.9%, p < 0.05). A total of 67 (68.4%) patients received oseltamivir, 89 (90.1%) was applied to antibiotics and 64 (65.3%) were treated with a combined therapy. Antiviral therapy was applied to 43 (43.3%) patients in the first 48 hours from the onset of the disease, of whom only one (3.4%) developed ARDS. Fatal outcome was noted in 2.0% of the patients (2 of 98 patients) and in 33.3% of the patients treated in the ICU. Conclusion. Novel influenza A (H1N1) is most commonly manifested as a mild acute respiratory disease, which usually affects young healthy adults. A small number of the patients develop severe illness with acute respiratory failure and death. Patients seem to have benefit from antiviral therapy especially in first 48 hours.

General Mechanisms of Antiviral Resistance

This chapter discusses the general mechanisms of antiviral resistance. Mammalian viruses represent a diverse group of infectious agents. The viruses that cause the common diseases of man and domestic animals comprise approximately 25 known families, which fall into groups according to their genome and replication strategies. Further evolution of modern viruses is continuing with mutations, recombinations, or reassortments. The use of vaccines has greatly reduced the burden of human disease caused by several other human viruses. Specific antiviral compounds have been developed for several of those viral infections that have not been adequately controlled by vaccines. Herpes viruses establish a latent state that enables the virus to remain in the host for a lifetime despite normal adaptive immune responses. Antivirals are effective at reducing virus replication during an acute episode. Another way in which a virus can establish a form of latency is by means of integration of a DNA copy of the genome. The virus has over 100 serotypes/genotypes. The mutation rate of a virus has been described as the probability that during a single replication of the virus genome a particular nucleotide position is altered. Several families of RNA virus have segmented genomes. Resistant variants are selected so quickly that a treated person can pass on resistant virus to contacts. Viruses are resistant to specific antiviral drugs. Although the genetic barrier needs to be increased for long-term delay in resistance in chronic infections, with any drug combination used in naturally self-limiting infections, the extra effect in reducing viral load quickly may well be a useful benefit. Our current antiviral therapies have been successful in reducing the burden of human diseases but many viruses have evolved strategies for countering new threats to their replication.

In vitro inhibitory activity of Alpinia katsumadai extracts against influenza virus infection and hemagglutination

Background

Alpinia katsumadai (AK) extracts and fractions were tested for in vitro antiviral activities against influenza virus type A, specially human A/PR/8/34 (H1N1) and avian A/Chicken/Korea/MS96/96 (H9N2), by means of time-of-addition experiments; pre-treatment, simultaneous treatment, and post treatment.

Results

In pre-treatment assay, the AK extracts and AK fractions did not show significant antiviral activity. During the simultaneous treatment assay, one AK extract and five AK fractions designated as AK-1 to AK-3, AK-5, AK-10, and AK-11 showed complete inhibition of virus infectivity against A/PR/8/34 (H1N1) and A/Chicken/Korea/MS96/96 (H9N2). The 50% effective inhibitory concentrations (EC₅₀) of these one AK extracts and five AK fractions with exception of the AK-9 were from 0.8 ± 1.4 to 16.4 ± 4.5 μg/mL against A/PR/8/34 (H1N1). The two AK extracts and three AK fractions had EC₅₀ values ranging from <0.39 ± 0.4 to 2.3 ± 3.6 μg/mL against A/Chicken/Korea/MS96/96 (H9N2). By the hemagglutination inhibition (HI) assay, the two AK extracts and five AK fractions completely inhibited viral adsorption onto chicken RBCs at less than 100 μg/mL against both A/PR/8/34 (H1N1) and A/Chicken/Korea/MS96/96 (H9N2). Interestingly, only AK-3 was found with inhibition for both viral attachment and viral replication after showing extended antiviral activity during the post treatment assay and quantitative real-time PCR.

Conclusions

These results suggest that AK extracts and fractions had strong anti-influenza virus activity that can inhibit viral attachment and/or viral replication, and may be used as viral prophylaxis.

Oseltamivir in seasonal, avian H5N1 and pandemic 2009 A/H1N1 influenza: pharmacokinetic and pharmacodynamic characteristics

Oseltamivir is the ester-type prodrug of the neuraminidase inhibitor oseltamivir carboxylate. It has been shown to be an effective treatment for both seasonal influenza and the recent pandemic 2009 A/H1N1 influenza, reducing both the duration and severity of the illness. It is also effective when used preventively. This review aims to describe the current knowledge of the pharmacokinetic and pharmacodynamic characteristics of this agent, and to address the issue of possible therapeutic drug monitoring. According to the currently available literature, the pharmacokinetics of oseltamivir carboxylate after oral administration of oseltamivir are characterized by mean ± SD bioavailability of 79 ± 12%, apparent clearance of 25.3 ± 7.0 L/h, an elimination half-life of 7.4 ± 2.5 hours and an apparent terminal volume of distribution of 267 ± 122 L. A maximum plasma concentration of 342 ± 83 μg/L, a time to reach the maximum plasma concentration of 4.2 ± 1.1 hours, a trough plasma concentration of 168 ± 32 μg/L and an area under the plasma concentration-time curve from 0 to 24 hours of 6110 ± 1330 μg · h/L for a 75 mg twice-daily regimen were derived from literature data. The apparent clearance is highly correlated with renal function, hence the dosage needs to be adjusted in proportion to the glomerular filtration rate. Interpatient variability is moderate (28% in apparent clearance and 46% in the apparent central volume of distribution); there is no indication of significant erratic or limited absorption in given patient subgroups. The in vitro pharmacodynamics of oseltamivir carboxylate reveal wide variation in the concentration producing 50% inhibition of influenza A and B strains (range 0.17-44 μg/L). A formal correlation between systemic exposure to oseltamivir carboxylate and clinical antiviral activity or tolerance in influenza patients has not yet been demonstrated; thus no formal therapeutic or toxic range can be proposed. The pharmacokinetic parameters of oseltamivir carboxylate after oseltamivir administration (bioavailability, apparent clearance and the volume of distribution) are fairly predictable in healthy subjects, with little interpatient variability outside the effect of renal function in all patients and bodyweight in children. Thus oseltamivir carboxylate exposure can probably be controlled with sufficient accuracy by thorough dosage adjustment according to patient characteristics. However, there is a lack of clinical study data on naturally infected patients. In addition, the therapeutic margin of oseltamivir carboxylate is poorly defined. The usefulness of systematic therapeutic drug monitoring in patients therefore appears to be questionable; however, studies are still needed to extend the knowledge to particular subgroups of patients or dosage regimens.

High levels and safety of oseltamivir carboxylate plasma concentrations after nasogastric administration in critically ill children in a pediatric intensive care unit

During the 2009 H1N1 influenza pandemics, the concentrations of oseltamivir (O) and its active metabolite (oseltamivir carboxylate [OC]) were determined in 11 children (1 month to 16 years of age) admitted to intensive care units for presumed severe H1N1 infection. They received oseltamivir phosphate (OP) nasogastrically at doses between 1.5 and 6.8 mg/kg of body weight. High OC concentrations were found, with a mean level of 678 ± 535 μg/liter. The mean OP concentration was 27 ± 52 μg/liter. No marked side effect was reported.

Comparison of combined nose-throat swabs with nasopharyngeal aspirates for detection of pandemic influenza A/H1N1 2009 virus by real-time reverse transcriptase PCR

Data assessing the diagnostic accuracies of use of different respiratory samples for the detection of the novel influenza A/H1N1 2009 virus by molecular methods are lacking. The objective of this study was to compare the sensitivity of combined nose and throat swabs (CNTS) with that of nasopharyngeal aspirates (NPA). This was a prospective study of adults and children with suspected influenza. Real-time reverse transcriptase PCR testing was used for the virological diagnosis. Of the 2,473 patients included, 264 with paired CNTS and NPA were randomly selected. Novel influenza A/H1N1 virus was identified in at least one sample for 115 (43.6%) patients, the majority of them young adults. In 109 patients (94.8%) the virus was identified in the CNTS, and in 98 (85.2%) it was identified in the NPA (P = 0.02). In 93 patients (80.1%), the virus was identified in both specimens. Spearman's rho correlation coefficient between the two methods was 0.82 (P < 0.001). There were no significant differences in accuracy between the specimens when patients were stratified according to demographic or clinical characteristics except in the case of women, in whom the sensitivity of CNTS was higher (P = 0.01). The combination of CNTS and NPA had a significantly higher sensitivity in identifying the virus than did each method alone (P = 0.02 for the comparison of the combination of both sampling methods with CNTS, and P < 0.001 for the comparison with NPA). We conclude that in patients with the novel influenza A/H1N1 virus, the diagnostic yield of CNTS is higher than that of NPA. The combination of both sampling methods increases the likelihood of diagnosing the virus.

Invasive aspergillosis after pandemic (H1N1) 2009

We report 2 patients with invasive aspergillosis after infection with pandemic (H1N1) 2009. Influenza viruses are known to cause immunologic defects and impair ciliary clearance. These defects, combined with high-dose corticosteroids prescribed during influenza-associated adult respiratory distress syndrome, may be novel risk factors predisposing otherwise immunocompetent patients to invasive aspergillosis.