Influenza Medication

Updated: Oct 12, 2017
  • Author: Hien H Nguyen, MD, MS; Chief Editor: Michael Stuart Bronze, MD  more...
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Medication

Medication Summary

The goals of pharmacotherapy are to reduce morbidity and to prevent complications. Agents include vaccines and antiviral drugs. The uricosuric agent probenecid may be used as an adjunct to antiviral treatment.

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Antivirals, Influenza

Class Summary

The antiviral drugs indicated for the treatment and chemoprophylaxis of influenza are the neuraminidase inhibitors (ie, oseltamivir and zanamivir). Neuraminidase inhibitors act directly on the viral proteins, decreasing the virulence of infection. Adamantanes (amantadine and rimantadine) were used in the past, but resistance against these agents has become widespread, and they are no longer recommended.

Oseltamivir (Tamiflu)

Oseltamivir inhibits neuraminidase, an enzyme that breaks the bond between newly produced virions and the host cell membrane. Specifically, neuraminidase—a glycoprotein located on the surface of the influenza virus—cleaves the attachment between hemagglutinin on the viral surface and the sialic acid receptor on the host cell membrane, thereby facilitating the release of the virion from the cell. Inhibition of neuraminidase thus decreases viral spread.

Oseltamivir is effective for the treatment of influenza A or B. It must be administered within 48 hours of symptom onset. The sooner it is taken after symptom onset, the better the effect. Oseltamivir reduces the length of illness by an average of 1.5 days. (In a subgroup of high-risk patients, illness was reduced by 2.5 days.) It also reduces the severity of symptoms. This agent is available as capsules (75, 45, and 30 mg) and as an oral suspension.

Oseltamivir resistance emerged in the United States during the 2008-2009 influenza season. Accordingly, zanamivir is now recommended as the initial choice for antiviral prophylaxis or treatment when influenza A infection or exposure is suspected.

A second-line alternative is to use a combination of oseltamivir and rimantadine rather than oseltamivir alone. Local influenza surveillance data and laboratory testing can assist the physician regarding antiviral agent choice.

The efficacy of oseltamivir against avian influenza is not well established.

Zanamivir (Relenza Diskhaler)

Zanamivir is an inhibitor of neuraminidase, an enzyme that breaks the bond between newly produced virions and the host cell membrane. Specifically, neuraminidase—a glycoprotein located on the surface of the influenza virus—cleaves the attachment between hemagglutinin on the viral surface and the sialic acid receptor on the host cell membrane, thereby facilitating the release of the virion from the cell. Inhibition of neuraminidase thus decreases viral spread.

This agent is effective against both influenza A and B; its efficacy against avian influenza is not well established. Severe and even fatal bronchospasm has been reported during treatment with zanamivir; consequently, this agent is not recommended for treatment or prophylaxis of influenza in individuals with underlying airway diseases (eg, asthma and chronic obstructive pulmonary disease).

Zanamivir is inhaled through a Diskhaler oral inhalation device. Circular foil disks that contain 5-mg blisters of drug are inserted into the supplied inhalation device.

Peramivir (Rapivab)

Peramivir elicits antiviral activity by inhibiting influenza virus neuraminidase, an enzyme that releases viral particles from the plasma membrane of infected cells. It is indicated for the treatment of acute uncomplicated influenza in adults who have been symptomatic for no more than 2 days. It is administered as a single 600 mg IV dose infused over 15-30 minutes.

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Vaccines, Inactivated, Viral

Class Summary

Influenza vaccine is administered each year before flu season. Typically, 3 virus strains (2 influenza A and 1 influenza B), which antigenically represent the influenza strains likely to circulate the next flu season, are included in the formulation each year. Quadrivalent vaccines that included 2 influenza A strains and 2 influenza B strains are available. The US Food and Drug Administration (FDA) makes the final decision about vaccine strains for influenza vaccines to be sold in the United States, based on year-round surveillance conducted by the US Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO). [53]

In April 2007, the FDA approved the first vaccine for H5N1 influenza (ie, avian influenza or bird flu). A second H5N1 influenza vaccine was approved by the FDA in November 2013. It contains the ASO3 adjuvant that allows a smaller amount of antigen to simulate an immune response. Each of these vaccines provides different viral strains; A/Vietnam/1203/2004 and A/Indonesia/05/2005 for the original and adjuvanted vaccines, respectively. H5N1 vaccines are available only to government agencies and for stockpiles.

Influenza virus vaccine trivalent (Afluria, Fluzone, Agriflu, Flucelvax, Fluarix, Fluvirin, Fluzone High-Dose, Fluzone Intradermal)

Influenza vaccine is indicated for active immunization to prevent infection from influenza A and B viruses. The vaccine induces antibodies specific to virus strains contained in the vaccine. The FDA determines influenza vaccine contents annually. Carefully check the indications and age ranges for various brands of influenza vaccine. For example, Fluzone is approved for children as young as 6 months, whereas Fluvirin is approved for children aged 4 years or older. Fluzone High-Dose is specifically formulated to provide a higher antigen content to evoke a stronger immune response in patients ≥65 years.

Influenza virus vaccine trivalent, recombinant (Flublok)

This vaccine is made from recombinant HA proteins that are not derived from egg or chick embryo. The CDC's Advisory Committee on Immunization Practices (ACIP) recommends FluBlok for vaccination of adults aged 18 y or older with egg allergy of any severity.

Influenza vaccine is indicated for active immunization to prevent infection from influenza A and B viruses. The vaccine induces antibodies specific to virus strains contained in the vaccine. The US Public Health Service determines influenza vaccine contents annually. Typically, 3 live attenuated virus strains, which antigenically represent the influenza strains likely to circulate the next flu season, are included in the formulation each year.

Influenza virus vaccine quadrivalent (Fluarix Quadrivalent, Fluzone Quadrivalent, FluLaval Quadrivalent)

Quadrivalent vaccines contain two strains of influenza A and two of influenza B. The vaccine induces antibodies specific to virus strains contained in vaccine. Each year, the US Public Health Service determines which viral strains will be included in the seasonal influenza vaccine that will antigenically represent the viral strains most likely to circulate in the next flu season. It is administered as an IM injection.

Influenza virus vaccine quadrivalent, recombinant (Flublok Quadrivalent)

Contains recombinant hemagglutinin (HA) proteins of the 4 strains of influenza virus specified by health authorities for inclusion in the annual seasonal vaccine. Contains no egg proteins, antibiotics, or preservatives.

Influenza virus vaccine trivalent, adjuvanted (Fluad)

Indicated for active immunization against influenza disease caused by influenza virus subtypes A and type B contained in the vaccine for adults aged ≥65 y. The vaccine is manufactured using an egg-based process. It is formulated with the adjuvant MF59, an oil-in-water emulsion of squalene oil. Squalene, a naturally occurring substance found in humans, animals, and plants, is highly purified for the vaccine manufacturing process. Adjuvants are incorporated into some vaccine formulations to enhance or direct the immune response of the vaccinated individual.

Influenza virus vaccine (H5N1)

The H5N1 inactivated virus vaccine induces antibodies against viral hemagglutinin, thereby blocking viral attachment to human respiratory tract epithelial cells. The vaccine is estimated to reduce the risk of contracting avian influenza by 45%. This vaccine is indicated for active immunization of adults at increased risk for exposure to the H5N1 influenza virus subtype A/Vietnam/1203/2004. [10]

Influenza virus vaccine (H5N1), adjuvanted

This vaccine contains the AS03 adjuvant. In clinical studies, the adjuvanted vaccine formulation stimulated the required immune response while using a smaller amount of antigen as compared to a formulation without adjuvant. It is indicated for active immunization for the prevention of disease caused by the influenza A virus H5N1 subtype A/Indonesia/05/2005.

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Vaccines, Live, Viral

Class Summary

Influenza vaccine is administered each year before flu season. The FDA makes the final decision about vaccine strains for influenza vaccines to be sold in the United States, based on year-round surveillance conducted by the CDC and the WHO. [53]

In June 2016, CDC’s Advisory Committee on Immunization Practices (ACIP) voted that live attenuated influenza vaccine (LAIV) should NOT be used during the 2016-2017 flu season. This recommendation has been extended by ACIP for the 2017-2018 influenza season. [50, 102] Data showed the estimate vaccine effectiveness among study participants in children aged 2-17 years against any flu virus was 3% (95% CI, -49% to 37%). [55]

Influenza virus vaccine quadrivalent, intranasal (FluMist Quadrivalent)

ALERT: CDC’s ACIP states intranasal flu vaccine should NOT be used during the 2017-2018 Northern Hemisphere influenza season.

In previous years, intranasal influenza vaccine was indicated for active immunization to prevent influenza A and B viruses in healthy children, adolescents, and adults aged 2 to 49 years.

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Uricosuric Agents

Class Summary

Agents that inhibit the tubular secretion of the active metabolite of oseltamivir may be used as adjunctive therapy with this antiviral drug.

Probenecid

Probenecid inhibits tubular secretion of the active metabolite of oseltamivir, reducing its clearance by approximately 50% and approximately doubling systemic exposure to oseltamivir. The appropriate dosing for combination therapy with probenecid and oseltamivir in the treatment of avian influenza has not been established.

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