Immunomodulator clarithromycin enhances mucosal and systemic immune responses and reduces re-infection rate in pediatric patients with influenza treated with antiviral neuraminidase inhibitors: a retrospective analysis

Challenges and Opportunities for Post-COVID Pulmonary Disease: A Focused Review of Immunomodulation

The resolution of the recent COVID-19 pandemic still requires attention, since the consequences of having suffered the infection, even in mild cases, are associated with several acute and chronic pathological conditions referred to as post-COVID syndrome (PCS). PCS often manifests with pulmonary disease and, in up to 9% of cases, a more serious complication known as post-COVID-19 pulmonary fibrosis (PC19-PF), which has a similar clinical course as idiopathic pulmonary fibrosis (IPF). Generating knowledge to provide robust evidence about the clinical benefits of different therapeutic strategies to treat the pulmonary effects of PCS can provide new insights to amplify therapeutic options for these patients. We present evidence found after a scoping review, following extended PRIMSA guidelines, for the use of immunomodulators in pulmonary PCS. We start with a brief description of the immunomodulatory properties of the relevant drugs, their clinically proven efficacy for viral infections and chronic inflammatory conditions, and their use during the COVID-19 pandemic. We emphasize the need for well-designed clinical trials to improve our understanding the physiopathology of pulmonary PCS and PC19-PF and also to determine the efficacy and safety of candidate treatments.

Stem cell therapy: a novel approach against emerging and re-emerging viral infections with special reference to SARS-CoV-2

The past several decades have witnessed the emergence and re-emergence of many infectious viral agents, flaviviruses, influenza, filoviruses, alphaviruses, and coronaviruses since the advent of human deficiency virus (HIV). Some of them even become serious threats to public health and have raised major global health concerns. Several different medicinal compounds such as anti-viral, anti-malarial, and anti-inflammatory agents, are under investigation for the treatment of these viral diseases. These therapies are effective improving recovery rates and overall survival of patients but are unable to heal lung damage caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Therefore, there is a critical need to identify effective treatments to combat this unmet clinical need. Due to its antioxidant and immunomodulatory properties, stem cell therapy is considered a novel approach to regenerate damaged lungs and reduce inflammation. Stem cell therapy uses a heterogeneous subset of regenerative cells that can be harvested from various adult tissue types and is gaining popularity due to its prodigious regenerative potential as well as immunomodulatory and anti-inflammatory properties. These cells retain expression of cluster of differentiation markers (CD markers), interferon-stimulated gene (ISG), reduce expression of pro-inflammatory cytokines and, show a rapid proliferation rate, which makes them an attractive tool for cellular therapies and to treat various inflammatory and viral-induced injuries. By examining various clinical studies, this review demonstrates positive considerations for the implications of stem cell therapy and presents a necessary approach for treating virally induced infections in patients.

Antibiotics with Antiviral and Anti-Inflammatory Potential Against Covid-19: A Review

In Covid-19 cases, elderly patients in long-term care facilities, children younger than five years with moderate symptoms, and patients admitted to ICU or with comorbidities are at a high risk of coinfection, as suggested by the evidence. Thus, in these patients, antibiotic therapy based on empirical evidence is necessary. Finding appropriate antimicrobial agents, especially with antiviral and anti-inflammatory properties, is a promising approach to target the virus and its complications, hyper-inflammation, and microorganisms resulting in co-infection. Moreover, indiscriminate use of antibiotics can be accompanied by Clostridioides difficile colitis, the emergence of resistant microorganisms, and adverse drug reactions, particularly kidney damage and QT prolongation. Therefore, rational administration of efficient antibiotics is an important issue. The main objective of the present review is to provide a summary of antibiotics with possible antiviral activity against SARS-CoV-2 and anti-immunomodulatory effects to guide scientists for further research. Besides, the findings can help health professionals in the rational prescription of antibiotics in Covid-19 patients with a high risk of co-infection.

Longitudinal Analysis of Neutralizing Potency against SARS-CoV-2 in the Recovered Patients after Treatment with or without Favipiravir

The effect of treatment with favipiravir, an antiviral purine nucleoside analog, for coronavirus disease 2019 (COVID-19) on the production and duration of neutralizing antibodies for SARS-CoV-2 was explored. There were 17 age-, gender-, and body mass index-matched pairs of favipiravir treated versus control selected from a total of 99 patients recovered from moderate COVID-19. These subjects participated in the longitudinal (>6 months) analysis of (i) SARS-CoV-2 spike protein’s receptor-binding domain IgG, (ii) virus neutralization assay using authentic virus, and (iii) neutralization potency against original (WT) SARS-CoV-2 and cross-neutralization against B.1.351 (beta) variant carrying triple mutations of K417N, E484K, and N501Y. The results demonstrate that the use of favipiravir: (1) significantly accelerated the elimination of SARS-CoV-2 in the case vs. control groups (p = 0.027), (2) preserved the generation and persistence of neutralizing antibodies in the host, and (3) did not interfere the maturation of neutralizing potency of anti-SARS-CoV-2 and neutralizing breadth against SARS-CoV-2 variants. In conclusion, treatment of COVID-19 with favipiravir accelerates viral clearance and does not interfere the generation or maturation of neutralizing potency against both WT SARS-CoV-2 and its variants.

Azithromycin in viral infections

Azithromycin (AZM) is a synthetic macrolide antibiotic effective against a broad range of bacterial and mycobacterial infections. Due to an additional range of anti-viral and anti-inflammatory properties, it has been given to patients with the coronaviruses SARS-CoV or MERS-CoV. It is now being investigated as a potential candidate treatment for SARS-CoV-2 having been identified as a candidate therapeutic for this virus by both in vitro and in silico drug screens. To date there are no randomised trial data on its use in any novel coronavirus infection, although a large number of trials are currently in progress. In this review, we summarise data from in vitro, murine and human clinical studies on the anti-viral and anti-inflammatory properties of macrolides, particularly AZM. AZM reduces in vitro replication of several classes of viruses including rhinovirus, influenza A, Zika virus, Ebola, enteroviruses and coronaviruses, via several mechanisms. AZM enhances expression of anti-viral pattern recognition receptors and induction of anti-viral type I and III interferon responses. Of relevance to severe coronavirus-19 disease (COVID-19), which is characterised by an over-exuberant innate inflammatory response, AZM also has anti-inflammatory properties including suppression of IL-1beta, IL-2, TNF and GM-CSF. AZM inhibits T cells by inhibiting calcineurin signalling, mammalian target of rapamycin activity and NFκB activation. AZM particularly targets granulocytes where it concentrates markedly in lysosomes, particularly affecting accumulation, adhesion, degranulation and apoptosis of neutrophils. Given its proven safety, affordability and global availability, tempered by significant concerns about antimicrobial stewardship, there is an urgent mandate to perform well-designed and conducted randomised clinical trials.

Possible mechanisms of action of clarithromycin and its clinical application as a repurposing drug for treating multiple myeloma

Clarithromycin (CAM), a semisynthetic macrolide antibiotic, is a widely used antibacterial drug. Recently, the efficacy of CAM as an add-on drug for treating multiple myeloma (MM) has been noted. Its effect on treating MM has been confirmed in combination chemotherapies that include CAM. However, a single treatment of CAM has no efficacy for treating MM. Many myeloma growth factors (MGFs) including interleukin (IL)-6 are known to be closely involved in the development of MM. CAM has been shown to suppress many MGFs, particularly IL-6. The possible mechanisms of action of CAM in treating MM have been suggested to include its immunomodulatory effect, autophagy inhibition, reversibility of drug resistance, steroid-sparing/enhancing effect and suppression of MGFs. In addition, MM is characterised by uncontrolled cell growth of monoclonal immunoglobulin (Ig)-producing neoplastic plasma cells. Large quantities of unfolded or misfolded Ig production may trigger considerable endoplasmic reticulum stress. Thus, MM is originally a fragile neoplasm particularly susceptible to autophagy-, proteasome- and histone deacetylase 6-inhibitors. Taken together, CAM plays an important role in MM treatments through its synergistic mechanisms. In addition, CAM with its pleiotropic effects on cytokines including IL-6 and indirect antiviral effects might be worth a try for treating COVID-19.

Clinical evidences on the antiviral properties of macrolide antibiotics in the COVID-19 era and beyond

Macrolides are a large group of antibiotics characterised by the presence of a macro-lactone ring of variable size. The prototype of macrolide antibiotics, erythromycin was first produced by Streptomyces and associated species more than half a century ago; other related drugs were developed. These drugs have been shown to have several pharmacological properties: in addition to their antibiotic activity, they possess some anti-inflammatory properties and have been also considered against non-bacterial infections. In this review, we analysed the available clinical evidences regarding the potential anti-viral activity of macrolides, by focusing on erythromycin, clarithromycin and azithromycin. Overall, there is no significant evidences so far that macrolides might have a direct benefit on most of viral infections considered in this review (RSV, Influenza, coronaviruses, Ebola and Zika viruses). However, their clinical benefit cannot be ruled out without further and focused clinical studies. Macrolides may improve the clinical course of viral respiratory infections somehow, at least through indirect mechanisms relying on some and variable anti-inflammatory and/or immunomodulatory effects, in addition to their well-known antibacterial activity.

[Review of current and future directions of antiviral therapy of influenza and acute respiratory viral infections in Russia]

AIM

to determine the perspectives for the use of drugs with combined antiviral, anti - inflammatory and immunomodulatory activity on the basis of medical studies of existing antiviral drugs for the treatment of influenza and acute respiratory viral infections in Russia.

MATERIALS AND METHODS

A brief review of the antiviral drugs used in Russia for the treatment of influenza and acute respiratory viral infections was conducted on the basis of 37 articles published in Scopus, Web of Science (WoS), and RSCI databases in the period from 1997 to 2018.

RESULTS

Resistance to neuraminidase inhibitors (oseltamivir, zanamivir), is slowly developing due to the mutations of the neuraminidase gene H275Y and Q136K. Most influenza A viruses remain resistant to adamantane antivirals. Repeated use of immunomodulators with indirect antiviral action leads to a hyporeactivity of the immune system and, subsequently, to a decrease in their effectiveness. Positive clinical and laboratory data in clinical trials were obtained using Enisamium iodide, a drug with combined action - direct antiviral, and immunomodulatory.

CONCLUSION

According to the WHO strategy, the results of the review demonstrate the need for continued research of medications with combined antiviral and pathogenetic effects on the infectious process caused by influenza and acute respiratory viral infections.

Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1 feeding enhances humoral immune responses, which are suppressed by the antiviral neuraminidase inhibitor oseltamivir in influenza A virus-infected mice

Antiviral neuraminidase inhibitors, such as oseltamivir, zanamivir, and peramivir, are widely used for treatment of influenza virus infection. We reported previously that oseltamivir inhibits the viral growth cycle, ameliorates symptoms, and reduces viral antigen quantities. Suppressed viral antigen production, however, induces a reduction of acquired antiviral humoral immunity, and increases the incidence of re-infection rate in the following year. To achieve effective treatment of influenza virus infection, it is necessary to overcome these adverse effects of antiviral neuraminidase inhibitors. Feeding of yogurt fermented with Lactobacillus delbrueckii ssp. bulgaricus (L. bulgaricus) OLL1073R-1 is reported to have immune-stimulatory effects on influenza virus infection in mice and humans. In the present study, we assessed the effect of feeding L. bulgaricus OLL1073R-1 yogurt cultures (YC) on local and systemic humoral immune responses, which were suppressed by oseltamivir treatment, in mice infected with influenza A virus. Yogurt culture (1.14 × 10⁸ cfu/0.4 mL per mouse per day) or sterile water (vehicle) was administered by intragastric gavage for 35 d. At d 22, influenza A virus/Puerto Rico/8/34 (H1N1) (PR8; 0.5 pfu/15 μL per mouse) was instilled intranasally, followed immediately by oral administration of oseltamivir (50 μg/100 μL per mouse, twice daily) or 5% methylcellulose (100 μL/mouse) as a vehicle for 13 d. Titers of anti-PR8-specific IgG and IgA in serum and mucosal secretory IgA (S-IgA) and IgG in bronchoalveolar lavage fluid (BALF) were analyzed by ELISA at 14 d after infection. Oseltamivir significantly suppressed the induction of anti-PR8-specific IgG and IgA in serum and S-IgA and IgG in BALF after infection. Feeding YC mildly but significantly stimulated production of PR8-specific IgA in serum, S-IgA in BALF, and IgG in serum without changing the IgG_2a:IgG₁ ratio. We analyzed the neutralizing activities against PR8 in serum and BALF and found that oseltamivir also reduced protective immunity, and YC feeding abrogated this effect. The immune-stimulatory tendency of YC on anti-PR8-specific IgA and IgG titers in serum and BALF was also detected in mice re-infected with PR8, but the effect was insignificant, unlike the effect of YC in the initial infection.

Macrolides in critically ill patients with Middle East Respiratory Syndrome

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More than one-third of critically ill patients with Middle East Respiratory Syndrome Coronavirus (MERS-CoV) received empiric therapy with macrolides.

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Macrolide therapy is not significantly associated with a reduction in 90-day mortality of critically ill patients with MERS-CoV.

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Macrolide therapy is not significantly associated with improvement in MERS-CoV RNA clearance of critically ill patients with MERS-CoV.

Objectives

Macrolides have been reported to be associated with improved outcomes in patients with viral pneumonia related to influenza and other viruses, possibly because of their immune-modulatory effects. Macrolides have frequently been used in patients with Middle East Respiratory Syndrome (MERS). This study investigated the association of macrolides with 90-day mortality and MERS coronavirus (CoV) RNA clearance in critically ill patients with MERS.

Methods

This retrospective analysis of a multicenter cohort database included 14 tertiary-care hospitals in five cities in Saudi Arabia. Multivariate logistic-regression analysis was used to determine the association of macrolide therapy with 90-day mortality, and the Cox-proportional hazard model to determine the association of macrolide therapy with MERS-CoV RNA clearance.

Results

Of 349 critically ill MERS patients, 136 (39%) received macrolide therapy. Azithromycin was most commonly used (97/136; 71.3%). Macrolide therapy was commonly started before the patient arrived in the intensive care unit (ICU) (51/136; 37.5%), or on day1 in ICU (53/136; 39%). On admission to ICU, the baseline characteristics of patients who received and did not receive macrolides were similar, including demographic data and sequential organ failure assessment score. However, patients who received macrolides were more likely to be admitted with community-acquired MERS (P = 0.02). Macrolide therapy was not independently associated with a significant difference in 90-day mortality (adjusted odds ratio [OR]: 0.84; 95% confidence interval [CI] :0.47–1.51; P = 0.56) or MERS-CoV RNA clearance (adjusted HR: 0.88; 95% CI:0.47–1.64; P = 0.68).

Conclusions

These findings indicate that macrolide therapy is not associated with a reduction in 90-day mortality or improvement in MERS-CoV RNA clearance.

Clarithromycin suppresses induction of monocyte chemoattractant protein-1 and matrix metalloproteinase-9 and improves pathological changes in the lungs and heart of mice infected with influenza A virus

The influenza A virus (IAV)-cytokine-trypsin/matrix metalloproteinase-9 (MMP-9) cycle is one of the important mechanisms of multiple organ failure in severe influenza. Clarithromycin, a macrolide antibiotic, has immune modulatory and anti-inflammatory effects. We analyzed the effects of clarithromycin on the induction of chemokines, cytokines, MMP-9, trypsin, vascular hyper-permeability and inflammatory aggravation in mice with IAV infection. IAV/Puerto Rico/8/34(H1N1) infection increased the levels of monocyte chemoattractant protein-1 (MCP-1) and cytokines in serum, and MMP-9 and trypsin in serum and/or the lungs and heart. Clarithromycin significantly suppressed the induction of serum MCP-1 and MMP-9 and vascular hyperpermeability in these organs in the early phase of infection, but did not suppress the induction of trypsin, IL-6 or IFN-γ. Histopathological examination showed that clarithromycin tended to reduce inflammatory cell accumulation in the lungs and heart. These results suggest that clarithromycin suppresses infection-related inflammation and reduces vascular hyperpermeability by suppressing the induction of MCP-1 and MMP-9.

Anti-inflammatory effects of adjunctive macrolide treatment in adults hospitalized with influenza: A randomized controlled trial

INTRODUCTION

- Macrolides can ameliorate inflammation in respiratory diseases, providing clinical benefits. Data in influenza is lacking.

METHOD

- A randomized, open-label, multicenter trial among adults hospitalized for laboratory-confirmed influenza was conducted. Study treatments of oseltamivir and azithromycin (500 mg/day), or oseltamivir alone, both for 5 days, were allocated at 1:1 ratio. The primary outcome was plasma cytokine/chemokine concentration change over time (Day 0-10); secondary outcomes were viral load and symptom score changes. Generalized Estimating Equation (GEE) models were used to analyze longitudinal data.

RESULTS

- Fifty patients were randomized to the oseltamivir-azithromycin or oseltamivir groups, with comparable baseline characteristics (age, 57 ± 18 years; A/H3N2, 70%), complications (72%), and viral load. Pro-inflammatory cytokines IL-6 (GEE: β -0.037, 95%CI-0.067,-0.007, P = 0.016; reduction from baseline -83.4% vs -59.5%), CXCL8/IL-8 (β -0.018, 95%CI-0.037,0.000, P = 0.056; -80.5% vs -58.0%), IL-17 (β -0.064, 95%CI-0.117,-0.012, P = 0.015; -74.0% vs -34.3%), CXCL9/MIG (β -0.010, 95%CI-0.020,0.000, P = 0.043; -71.3% vs -56.0%), sTNFR-1, IL-18, and CRP declined faster in the oseltamivir-azithromycin group. There was a trend toward faster symptom resolution (β -0.463, 95%CI-1.297,0.371). Viral RNA decline (P = 0.777) and culture-negativity rates were unaffected. Additional ex vivo studies confirmed reduced induction of IL-6 (P = 0.017) and CXCL8/IL-8 (P = 0.005) with azithromycin.

CONCLUSION

- We found significant anti-inflammatory effects with adjunctive macrolide treatment in adults with severe influenza infections. Virus control was unimpaired. Clinical benefits of a macrolide-containing regimen deserve further study. [ClinicalTrials.gov NCT01779570].

Mechanistic perspective of the oxido-immunopathologic resolution property of kolaviron in mice influenza pneumonitis

Implicated in influenza-associated pathology are innate defence overzealousness and unabated secretion of oxidative tissue-sensitive antimicrobial agents. At different time points, mice were pre-treated with kolaviron (400 mg/kg), a natural antioxidant and anti-inflammatory agent, and subsequently challenged with 2 LD₅₀ influenza A/H3N2/Perth/16/09 virus. After euthanasia at day 6, blood, lungs, liver and spleen were collected and processed for biochemical, immunohistochemical and flow cytometric assessment of redo-inflammatory imbalance, cytokine storm indices and T helper 1 host response. Previously kolaviron was reported to delay mortality onset, improve morbidity and attenuate myeloperoxidase activity and nitric oxide production with minimal impact on viral clearance. This study additionally confirmed nitric oxide, but not hydrogen peroxide, as the major culprit implicated in influenza virus-induced oxido-pathology. Systemic effect of the sustained inflammation and nitrosative stress was more prominent in the spleen and lung than in the liver of mice infected with A/H3N2/Perth/16/09. Influential to immunopathology was heightened pulmonary expression of IL-1β, RANTES, IL-10, MCP-1, NF-κB, iNOS and COX-2. However, kolaviron combated the influenza-established nitrative stress, reversed the elicited cytokine storm and restored the oxidized environment to a reductive milieu. Our data also suggest that kolaviron administration early in infection may foster CD4⁺ response. These data indicate that kolaviron may confer disease-dwindling properties during acute influenza infection via a system-wide protective approach involving multiple targets especially at the early stage of the infection.

Impact of oseltamivir use on the reduction of complications in patients with influenza: a prospective study

To evaluate the factors associated with oseltamivir prescription and to study the effectiveness of oseltamivir in reducing influenza-related complications. A prospective cohort study using the SOS Doctors (a network of physicians who perform house-call visits in Attica, Greece). Patients with confirmed or clinically suspected influenza were followed up to 14 days during the 2011-2012 influenza period. 410 patients with confirmed or suspected influenza were included. Healthy adults were mainly enrolled, with a median age of 44 years. Influenza diagnosis was mainly based on clinical criteria (65.8 % of patients). Oseltamivir was prescribed for 45.4 % of them. In a multivariate analysis, prescription of oseltamivir was associated with the attending physician (p < 0.001), positive influenza test (p < 0.001) and diabetes (p = 0.027). Data on complications were available for 351 patients, and 50 (15.8 %) of them reported at least one. Seven patients required hospitalization. Types of complications (pneumonia, bronchitis, etc.) were not significantly different between patients receiving and those not receiving oseltamivir. In the multivariate analysis, higher oseltamivir prescription rate was associated with fewer complications (p < 0.001). Bearing in mind the limitations of a non-randomized study, in a real-life setting, oseltamivir prescription and the rate of complications in patients with influenza were associated with the attending physician, underlying diseases and diagnostic tests. Overall, when the frequency of oseltamivir prescription increased, the influenza-related complications decreased.

The mechanisms of delayed onset type adverse reactions to oseltamivir

Oseltamivir is recommended for the treatment and prophylaxis of influenza in persons at higher risk for influenza complications such as individuals with diabetes, neuropsychiatric illnesses, and respiratory, cardiac, renal, hepatic or haematological diseases. However, a recent Cochrane review reported that reduction of antibody production, renal disorders, hyperglycaemia, psychiatric disorders, and QT prolongation may be related to oseltamivir use. The underlying mechanisms are reviewed. There is decisive evidence that administration of a clinically compatible dose of oseltamivir in mice challenged by a respiratory syncytial virus (RSV) that lacks a neuraminidase gene showed symptom-relieving effects and inhibition of viral clearance. These effects were accompanied by decreased level of T cell surface sialoglycosphingolipid (ganglioside) GM1 that is regulated by the endogenous neuraminidase in response to viral challenge. Clinical and non-clinical evidence supports the view that the usual dose of oseltamivir suppresses pro-inflammatory cytokines such as interferon-gamma, interleukin-6, and tumour necrosis factor-alpha almost completely with partial suppression of viral shedding in human influenza virus infection experiment. Animal toxicity tests support the clinical evidence with regard to renal and cardiac disorders (bradycardia and QT prolongation) and do not disprove the metabolic effect. Reduction of antibody production and cytokine induction and renal, metabolic, cardiac, and prolonged psychiatric disorders after oseltamivir use may be related to inhibition of the host’s endogenous neuraminidase. While the usual clinical dose of zanamivir may not have this effect, a higher dose or prolonged administration of zanamivir and other neuraminidase inhibitors may induce similar delayed reactions, including reduction of the antibody and/or cytokine production.

The administration of oseltamivir results in reduced effector and memory CD8+ T cell responses to influenza and affects protective immunity

The clinical benefits of oseltamivir (Tamiflu) are well established, but the effects of antiviral treatment on the immune response are poorly understood. By use of flow cytometric analyses and the mouse model, we thoroughly investigated the impact of such a treatment on the immune response and the generation of protective immunity to influenza. We demonstrated that influenza-specific CD8(+) effector T cell recruitment was reduced up to 81% in the lungs of mice treated with oseltamivir (5 or 50 mg/kg twice daily; EC50 49 nM in vitro) compared to saline controls, but cell generation was unaffected in draining lymph nodes. Importantly, we showed that oseltamivir administration significantly decreased the pools of tissue-resident and circulating effector memory (93.7%) and central memory CD8(+) T cells (45%) compared to saline controls. During heterologous secondary infection, a decreased memory CD8(+) T cell pool combined with reduced generation of secondary influenza-specific effectors in the lymph nodes resulted in 10-fold decreased CD8(+) T cell recall responses, which increased mouse morbidity and delayed viral clearance. Furthermore, antiviral administration led to a significant 5.7-fold decreased production of functional anti-influenza antibodies. Thus, our study demonstrates that antiviral treatment affects the development of the adaptive immune response and protective immunity against influenza.

Seasonal Human Influenza: Treatment Options

Seasonal influenza can be a self-limiting illness in healthy individuals but is associated with short-term morbidity and economic burden. Influenza can cause significant morbidity and mortality in young children, the elderly, pregnant and post-partum women, patients with co-morbidities and the immunocompromised. Neuraminidase inhibitors (NAIs) are the treatment of choice for influenza due to widespread resistance to the adamantanes. NAIs are efficacious for the treatment of influenza in ambulatory patients with mild illness, when initiated within 48 h of symptom onset. Early treatment with NAIs has been shown to reduce otitis media in children, and lower respiratory tract complications, resulting in antibiotic therapy, in adults. Evidence on the efficacy of NAIs for the prevention of influenza-related complications in at-risk populations, based on reviews of data from randomised trials is inconclusive. However, observational studies suggest that in hospitalised patients early treatment with NAIs has been associated with reduced mortality. NAIs should be initiated as soon as possible in patients at high-risk of influenza-related complications, with suspected or proven influenza, hospitalised patients and patients with severe or progressive disease. NAIs can be considered in previously healthy patients when therapy can be initiated within 48 h of symptom onset. In previously healthy patients, the therapeutic efficacy of oseltamivir is time-dependent, with maximal benefit observed when therapy is initiated within 48 h of symptom onset. However, several observational studies suggest therapeutic benefit beyond 48 h, in hospitalised patients, severe disease, and patients at high risk of complications, including pregnant women. NAIs should be considered in patients at high risk of influenza-related complications who present late. Further studies are needed to define the optimal timing of NAIs. Oseltamivir-resistant virus has been widely reported but is predominantly an issue in H1N1 seasonal influenza. Zanamivir-resistant influenza virus is rare, and inhaled or intravenous (IV) zanamivir is the treatment of choice in proven or suspected oseltamivir-resistant virus. Intubated patients with severe influenza can be treated with oseltamivir (suspension) administered via nasogastric tube. The commercial dry powder formulation of zanamivir should not be administered, via nebulisation, as it has been associated with ventilator malfunction and mortality. In intubated patients, when there are concerns about gastric absorption, IV zanamivir should be obtained under Emergency Investigational New Drug access schemes. Currently available evidence does not support the use of high-dose or extended-duration oseltamivir in patients with severe influenza, but does require further investigation. Extracorporeal membrane oxygenation has not been shown to be superior to conventional management in patients with influenza-associated acute respiratory distress syndrome and should be considered as salvage therapy. Corticosteriods should not be used in the treatment of severe influenza as this has been associated with increased risk of mortality and bacterial superinfection.