Know When to Prescribe an Antiviral

Know When to Prescribe an Antiviral


Flu season is back and vaccinating continues to be the best way to protect ourselves and our patients against serious complications from the flu.[1] Patients should only receive the intramuscular vaccine; intranasal flu vaccine is not effective for the 2016-2017 flu season.1 Patients 17 and younger should be offered the flu vaccine during office visits, while those 18 years and older also have the option of receiving it at pharmacies.

Treatment (Antiviral and Supportive)

Patients who are high risk for complications and appear to have influenza should be considered for early antiviral treatment, independent of laboratory confirmation or influenza vaccine status. [2] This includes:

  • Pregnant and postpartum women
  • Children younger than 2 years
  • Persons with chronic illness such as asthma, diabetes, sickle cell disease, or seizure disorders
  • Persons with neurodevelopmental disorders such as cerebral palsy and intellectual disability
  • Persons with immunosuppression
  • Children on long-term aspirin therapy

Clinical benefit is greatest when antiviral therapy is started within 48 hours of influenza illness onset.[3] When given within 48 hours of symptom onset, studies show oseltamivir reduces illness duration by one day.[4] Initiation of antiviral treatment beyond 48 hours of symptom onset may have additional benefit for hospitalized patients, pregnant women, and patients with complicated/severe illness.[5] Antiviral therapy has been shown to offer minimal or no benefit in healthy children and adults when initiated more than 2 days after onset of uncomplicated influenza.[6] Apply the principles of antimicrobial stewardship when prescribing antiviral therapy to prevent drug resistant flu.[7],[8] Antiviral therapy should not be a substitute for vaccination.

Relenza (zanamivir) and Tamiflu (oseltamivir) are antivirals recommended by the FDA and covered by Texas Medicaid with activity against influenza A and B.[9] Both antivirals are indicated for patients who have been symptomatic for no more than 48 hours and treatment duration is five days. [10]

Relenza (zanamivir)[11]

  • Dispensed as an orally inhaled powder.
  • May be a good choice for patients who do not tolerate the GI-related side effects of other antivirals/antibiotics or have difficulty taking suspensions with strong taste.
  • Approved for treatment in ages 7 and older and prophylaxis in ages 5 and older.
  • Not recommended for patients with asthma or an underlying respiratory disease.
  • Common side effects include sinusitis, dizziness, and bronchospasm.
  • Like Tamiflu, Relenza is a neuraminidase inhibitor and may be a good alternative if Tamiflu resistant flu is suspected.

Tamiflu (oseltamivir)[12]

  • Available as a capsule or oral suspension.
  • Approved for treatment in all ages and prophylaxis in children 3 months or older.
  • Nausea, vomiting, and diarrhea are the most common side effects, occurring in 15% of patients.
  • Counsel patients to take Tamiflu with food to reduce GI-related side effects.


Chemoprophylaxis should not be considered a substitute for vaccination. CDC’s Advisory Committee for Immunization Practices (ACIP) recommends chemoprophylaxis for the following[13]:

  • Post exposure prophylaxis may be considered for family or close contacts of suspected or confirmed cases who are at higher risk of flu complications, and who have not received the flu shot
  • Post exposure prophylaxis may be considered for unvaccinated healthcare workers who have had occupational exposure without protective equipment
  • Pre-exposure prophylaxis should only be used for persons at very high risk of flu complications who cannot be otherwise protected at times of high risk for exposure
  • Prophylaxis should also be administered to all eligible residents of institutions that house patients at high risk when needed to control outbreaks



[2] Antiviral Therapy and Prophylaxis for Influenza in Children Committee on Infectious Diseases Pediatrics Apr 2007, 119 (4) 852-860; DOI: 10.1542/peds.2007-0224


[4] Fry AM, Goswami D, Nahar K, Sharmin AT, Rahman M, Gubareva L, Azim T, Bresee J, Luby SP, Brooks WA. Efficacy of oseltamivir treatment started within 5 days of symptom onset to reduce influenza illness duration and virus shedding in an urban setting in Bangladesh: a randomised placebo-controlled trial. Lancet Infect Dis. 2014 Feb;14(2):109-18. doi: 10.1016/S1473-3099(13)70267-6.







[11] Lexicomp Online® , Pediatric & Neonatal Lexi-Drugs® , Hudson, Ohio: Lexi-Comp, Inc.; January 17, 2017.

[12] Lexicomp Online® , Pediatric & Neonatal Lexi-Drugs® , Hudson, Ohio: Lexi-Comp, Inc.; January 17, 2017.


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