Pneumonia - Prevention

Anti-Viral Drugs: Neuraminidase Inhibitors

Brands and Benefits. Zanamivir (Relenza) and oseltamivir (Tamiflu) are called neuraminidase inhibitors. They are newer agents that have been designed to block a key viral enzyme called neuraminidase, which helps viruses spread (replicate).

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Both zanamivir and oseltamivir have the following benefits:

Neuraminidase inhibitors are effective for treating both A and B strains of influenza. M2 inhibitors, which prevent the virus from reproducing, are only effective against type A.
They shorten the duration of the flu by one to three days.
They may help reduce transmission of the virus, although evidence is needed to confirm these findings.
They may have a lower risk than M2 inhibitors for emerging viral strains that are resistant to their effects. In fact, on January 14 2006, the Centers for Disease Control and Prevention (CDC) released a Heath Alert (the highest level of importance) regarding the use of M2 inhibitors (amantadine and rimantadine) for the prevention or treatment of flu. Due to significant increase in Influenza A resistance to this class of antiviral medication, the CDC recommended against its use for the remainder of the 2005-2006 flu season.
They may reduce complications of influenza, although this needs to be confirmed. It is not yet known if they have any effect on overall survival rates.
They have fewer serious side effects than the M2 inhibitors.
Both have some benefits for preventing influenza. Only oseltamivir has been approved for this purpose, however, and only in people over 13.

Limitations and Side Effects. Although they have many advantages compared to the M2 inhibitors, they are much more expensive. They also need to be taken within two days of symptoms to be effective. There are also some differences between the two agents that could be significant for some individuals:

Zanamivir (Relenza) is administered as a nasal spray or inhaler. People with asthma or other lung disorders may experience airway spasms and should use this drug with caution. Side effects are generally minor in most patients. Of concern, however, was a 2001 British study, which found that a majority of elderly patients were not able to properly use the zanamivir (Relenza) inhaler device, making the medicine virtually ineffective in these cases. The study was small, however, and other reports suggest that zanamivir is sill effective in this older group.
Oseltamivir comes in capsule and liquid form. Side effects are also minor, but about 10 - 15% of patients experience nausea and vomiting. Patients with kidney dysfunction should take lower doses.

Antiviral Drugs for Prevention of The Flu

To date both M2 inhibitors and oseltamivir have been approved for prevention of influenza.

M2 inhibitors. Amantadine and rimantadine protect against the influenza A infection itself in about half of individuals. Rimantadine is preferred for prevention during outbreaks of influenza A because it has fewer adverse side effects.
Neuraminidase Inhibitors. Both zanamivir (Relenza) and oseltamivir (Tamiflu) help prevent both influenza A and B. Only oseltamivir has been approved for this purpose, however, and only in people over 13. Both appear to be very effective in preventing influenza in people who have been exposed to family members with the flu.

Antiviral drugs are not a substitute for vaccines. But,they are extremely important add-ontherapy for peoplein certain high-risk groups. They may also be used:

In combination with the flu vaccine during seasons where there is a poor match between the virus and vaccine.
In high-risk individuals who are vaccinated after the flu season has started. In such cases, it takes about two weeks (or longer in children) for the vaccine to take effect. The anti-viral drugs offer protection during that period.
As supplementary protection for vaccinated people in high-risk groups, such as the elderly or people with compromised immune systems.
In people who cannot have vaccinations for whatever reason.
For people who provide care for high-risk individuals.
For high-risk individuals who cannot or will not be vaccinated.