Thursday, December 21, 2017

CDC: Influenza Antiviral Medications - Summary for Clinicians


Because of the bad rap they've gotten over the past 10 years, some doctors (and many patients) may fail to recognize the importance of early administration of antivirals to at-risk patients with severe influenza. 
Despite headlines, such as the Daily Mail’s bombastic Ministers blew £650MILLION on useless anti-flu drugs, the preponderance of evidence shows that antivirals do lessen both the severity and duration of severe influenza, and can be life-saving for some patients.  
We've gone over these studies before, but a quick perusal of these earlier blogs can serve as a refresher:
CID Journal: Early Administration Of NAIs Improves Survivability Of H7N9 Patients
ECDC: Expert Opinion On Use Of Neuraminidase Inhibitor Antivirals For Influenza

EID Journal: Revisiting The Oseltamivir Effectiveness Debate

Wellcome Trust/AMS Report On Antivirals For Influenza

CID Journal: Outcomes Of Prompt Influenza Antiviral Treatment Of Older Adults

During a severe H3N2 flu season such as appears likely this winter - where the elderly may be disproportionately affected and seasonal flu vaccine may provide only modest protection -  the importance of aggressive treatment is paramount.
Yesterday the CDC posted an extensive review of influenza antiviral medications for both treatment and chemoprophylaxis.
While the technical details are mostly of interest to clinicians, it is important that those who are at higher risk of complications know to contact their doctors immediately when they are sickened, since antivirals are most effective when taken during the first 48 hours.

Influenza Antiviral Medications: Summary for Clinicians

On This Page

The information on this page should be considered current for the 2017-2018 influenza season for clinical practice regarding the use of influenza antiviral medications.
This page contains excerpts from Antiviral Agents for the Treatment and Chemoprophylaxis of Influenza – Recommendations of the Advisory Committee on Immunization Practices (ACIP). PDF Version[1 MB, 28 Pages]
Antiviral medications with activity against influenza viruses are an important adjunct to influenza vaccine in the control of influenza.
  • Influenza antiviral prescription drugs can be used to treat influenza or to prevent influenza.
  • Five licensed prescription influenza antiviral agents are available in the United States.
  • Three influenza antiviral medications approved by the U.S. Food and Drug Administration (FDA) are recommended for use in the United States during the 2017-2018 influenza season: oral oseltamivir (available as a generic version or under the trade name Tamiflu®), inhaled zanamivir (trade name Relenza®), and intravenous peramivir (trade name Rapivab®). These drugs are chemically related antiviral medications known as neuraminidase inhibitors that have activity against both influenza A and B viruses. Generic oseltamivir was approved by the FDA in August 2016 and became available in December of 2016.
  • Amantadine and rimantadine are antiviral drugs in a class of medications known as adamantanes. These medications are active against influenza A viruses, but not influenza B viruses. As in recent past seasons, there continues to be high levels of resistance (>99%) to adamantanes among circulating influenza A(H3N2) and influenza A(H1N1)pdm09 (“2009 H1N1”) viruses. Therefore, amantadine and rimantadine are not recommended for antiviral treatment or chemoprophylaxis of currently circulating influenza A viruses.
  • Antiviral resistance to oseltamivir, zanamivir, and peramivir among circulating influenza viruses is currently low, but this can change. Also, antiviral resistance can emerge during or after treatment in some patients (e.g., immunocompromised).
  • For information about antiviral drug resistance to influenza viruses and guidance on the use of influenza antiviral medications when antiviral resistance is suspected or documented this season, see Antiviral Drug-Resistance among Influenza Viruses.
  • For weekly surveillance data on antiviral resistance this season, see the FluView U.S. Influenza Surveillance Report.

While their value in treating mild to moderate influenza in healthy adults is debatable, early treatment with antivirals have shown great value when treating patients who:
  • are hospitalized;
  • have severe, complicated, or progressive illness, or; 
  • are at higher risk for influenza complications.
The CDC considers those a `higher risk' to include:

Persons at higher risk for influenza complications recommended for antiviral treatment include:

  • children aged younger than 2 years;1
  • adults aged 65 years and older;
  • persons with chronic pulmonary (including asthma), cardiovascular (except hypertension alone), renal, hepatic, hematological (including sickle cell disease), and metabolic disorders (including diabetes mellitus), or neurologic and neurodevelopment conditions (including disorders of the brain, spinal cord, peripheral nerve, and muscle, such as cerebral palsy, epilepsy [seizure disorders], stroke, intellectual disability [mental retardation], moderate to severe developmental delay, muscular dystrophy, or spinal cord injury);
  • persons with immunosuppression, including that caused by medications or by HIV infection;
  • women who are pregnant or postpartum (within 2 weeks after delivery);
  • persons aged younger than 19 years who are receiving long-term aspirin therapy;
  • American Indians/Alaska Natives;
  • persons who are morbidly obese (i.e., body mass index is equal to or greater than 40); and
  • residents of nursing homes and other chronic care facilities.

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