Which medications are used for treatment of influenza A and B pneumonia?

Updated: Mar 24, 2021
  • Author: Zab Mosenifar, MD, FACP, FCCP; Chief Editor: John J Oppenheimer, MD  more...
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Amantadine hydrochloride and rimantadine hydrochloride are approved for the prevention and treatment of influenza A virus infection. They are not active against influenza B virus infection. Both drugs are absorbed well orally, block the viral M2 protein ion channel, and inhibit the uncoating of the virus. Rimantadine is a synthetic analog of amantadine and has comparable therapeutic efficacy.

Treatment with these compounds has been associated with the emergence of viral resistance. The clinical significance of this is not known. Many of the current strains are not susceptible to amantadine/rimantadine (including H1N1 influenza virus), so empiric use of these agents as the only drug is not recommended.

Oseltamivir, zanamivir, and peramivir block the neuraminidase surface protein on both influenza A and influenza B viruses. [78, 79, 80, 81, 82, 83]

These drugs trap the virus inside the infected respiratory epithelial cells and prevent spread to other cells. They are active against both influenza A and influenza B viruses. These newer drugs have a different safety profile and lower potential for inducing resistance, but they are much more expensive.

Peramivir (Rapivab) was approved by the FDA in December 2014 for use in adults as a single 600 mg IV dose. It has since been approved for children aged 6 months and older. In clinical trials, a single intravenous dose of peramivir, a sialic acid analogue and a selective inhibitor of neuraminidases produced by influenza A and B viruses, is effective and well tolerated in subjects with uncomplicated seasonal influenza virus infection. At both 300 mg and 600 mg, peramivir significantly reduced the time to alleviation of symptoms in comparison with placebo. [84] Additional data from over 2,700 subjects treated with peramivir in 27 clinical trials also supported its approval. It was available in the United States by emergency protocol during the 2009 H1N1 influenza pandemic.

The results of zanamivir studies have confirmed its efficacy only if therapy is started within 24-48 hours of symptom onset in febrile patients. Most studies have reported a similar window of opportunity for oseltamivir. Like the older agents, they reduce the course of influenza by approximately one day. Oseltamivir resistance emerged in the United States during the 2008-2009 influenza season.

For severe influenza pneumonia, antiviral medication should be given, even after the 48-hour window.

In a double-blind, randomized controlled trial, one inhalation of laninamivir octanoate was shown as effective for the treatment of seasonal influenza in adults. Effectiveness was also shown for the oseltamivir-resistant virus. [85]

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