This years flu vaccine was disappointing in its coverage of the influenza strains making folks sick. Because of this, we may have to rely instead on the antiviral medications used to treat influenza. Influenza medications are moderately effective for reducing the duration and severity of influenza when started at the onset of symptoms. These antiviral meds also help reduce the duration of viral shedding, important for limiting spread from person to person.
- Tamiflu (oseltamivir) is a capsule taken as 75 mg daily for 5 days. Tamiflu has been shown in studies to shorten the duration of influenza symptoms by 1.5 to 2 days. Some studies have shown a mortality reduction and shorter length of hospitalization in patients with severe influenza treated with Tamiflu. Tamiflu has been shown to be effective against both Influenza A and B.
- Relenza (zanamivir) is an oral inhaler and cannot be used in patients with underlying asthma or other chronic respiratory conditions. Relenza has also been shown in studies to reduce the duration of symptoms of influenza by 1.3 days in otherwise healthy adults ≤ 65 years of age, and by 2 days in adults ≥ 65 years of age. As is true with Tamiflu, if you start Relenza within 30 hours of the onset of your symptoms you will see more benefit with a three day shortening of major symptoms (from 7 to 4 days). There appears to be no benefit in starting Relenza if you’ve already been sick for 30 hours.
- Rapivab (peramivir) is the newest of the influenza medications just approved in December 2014 for use in people with influenza who have seen sick for 2 days or less. It is the first one that is administered intravenously (through an IV). Peramivir is administered as a single intravenous dose of 600 mg because it has strong and prolonged affinity for influenza virus. Patients who received Rapivab had their influenza symptoms alleviated an average of 21 hours sooner and became afebrile (no longer had a fever) approximately 12 hours sooner than those who received a placebo.
Which one is the best?
There aren’t many comparison studies but Rapivab was compared to Tamiflu and found to be “non-inferior” meaning they both work about the same to limit duration of symptoms. Remember, Relenza can’t be used in anyone with asthma. Tamiflu can also cause nausea and vomiting, and diarrhea is a common adverse effect reported in patients receiving Rapivab. One really isn’t better than the other so look at delivery method (inhaler, pill, IV), cost, and side effect profile with your doctor to make the decision.
Can the influenza virus be resistant to these medications?