| According to a recent report on influenza
| |
| | adults. Once-daily oseltamivir for seven
|
| in the Journal of Virology, "Although
| |
| | to 10 days is also effective for
|
| vaccination is the ideal way to reduce
| |
| | post-exposure prophylaxis in household
|
| the interspecies spread of influenza
| |
| | contacts, including children, and when
|
| viruses, the preparation of a new vaccine
| |
| | ill index cases receive concurrent
|
| takes six months or more. In the
| |
| | treatment.
|
| interim, antiviral drugs are the only
| |
| | Relenza (zanamivir; the second choice for
|
| option."
| |
| | treatment of bird flu)
|
| Antiviral drugs can be used for both
| |
| | 1. Prescription antiviral medication
|
| treatment and prevention of H5N1 bird
| |
| | approved for treatment of seasonal
|
| flu, but have significant limitations.
| |
| | influenza by the FDA.
|
| These drugs are expensive, supplies of
| |
| | 2. Mechanism of action: neuraminidase
|
| them are limited, they have to be given
| |
| | inhibitor. (It is a potent and specific
|
| within a short time period to be
| |
| | inhibitor of the neuraminidase activity
|
| effective, and resistance either has
| |
| | of influenza A and B viruses. Compared
|
| already developed or can develop at any
| |
| | to oseltamivir, zanamivir is more active
|
| time. Even under optimal circumstances,
| |
| | against influenza B but less active
|
| none of them are 100 percent effective.
| |
| | against influenza A/N2 neuraminidases of
|
| There are four antivirals that are
| |
| | clinical isolates, although the clinical
|
| approved by the U.S. Food and Drug
| |
| | importance of such differences is
|
| Administration (FDA) for use against
| |
| | uncertain. Zanamivir is inhibitory for
|
| influenza-two older and inexpensive
| |
| | certain influenza A neuraminidase
|
| drugs, amantadine and rimantadine, to
| |
| | variants that are resistant to
|
| which the bird-flu virus has developed
| |
| | oseltamivir.) [Emphasis added.]
|
| significant resistance-and two newer,
| |
| | 3. Available forms: Not available in
|
| more expensive and more effective drugs,
| |
| | tablet or pill form; available only for
|
| Roche's oseltamivir (brand name:
| |
| | oral inhalation with a proprietary
|
| Tamiflu), and GlaxoSmithKline's zanamivir
| |
| | Diskhaler device.
|
| (brand name: Relenza; must be inhaled).
| |
| | NOTE: The proprietary inhaler device for
|
| The two new drugs belong to a class of
| |
| | delivering zanamivir is breath-activated
|
| antiviral agents called neuraminidase
| |
| | and requires a cooperative, trained
|
| inhibitors. Tamiflu works by blocking the
| |
| | patient. The use of the Diskhaler device
|
| action of a specific enzyme, known as
| |
| | is not reliable in young children, very
|
| neuraminidase, on the surface of the
| |
| | infirm or elderly persons, or those
|
| influenza virus to prevent it from
| |
| | cognitively impaired. Although the
|
| spreading and infecting other cells in
| |
| | inhaler has been used effectively in
|
| the body.
| |
| | older adults, over half of hospitalized
|
| Amantadine was once effective against
| |
| | older adults could not correctly use the
|
| H5N1, but its effectiveness has
| |
| | device after instruction.
|
| diminished drastically because the virus
| |
| | 4. Effective only if given within 48
|
| has developed resistance against it.
| |
| | hours of onset of symptoms.
|
| There is some indication, however, that a
| |
| | 5. FDA-approved for treatment for those
|
| combination of Tamiflu and amantadine
| |
| | seven years and older.
|
| might be more effective than Tamiflu
| |
| | 10 mg (two inhalations) twice
|
| alone. Information about Tamiflu and
| |
| | daily for five days.
|
| Relenza is summarized below:
| |
| | 6. Not FDA-approved for prophylaxis
|
| Tamiflu (oseltamivir; the first choice
| |
| | (prevention) of seasonal influenza (but
|
| for prevention or treatment of bird flu)
| |
| | may be effective).
|
| 1. Prescription antiviral medication
| |
| | 7. Side effects: Inhaled zanamivir is
|
| approved for treatment of seasonal
| |
| | generally well tolerated, and the
|
| influenza by the Food and Drug
| |
| | frequency of complaints is not
|
| Administration (FDA). Note that use of
| |
| | significantly different from those in
|
| Tamiflu for treatment or prevention of
| |
| | placebo [sugar pill] recipients among
|
| avian influenza (bird flu) is an
| |
| | adults and children aged five years and
|
| "off-label" use of the medication, that
| |
| | older.
|
| is, a use that has not been officially
| |
| | However, post-marketing reports indicate
|
| approved by the FDA. However, Tamiflu is
| |
| | a potential risk for acute bronchospasm,
|
| widely recognized as the best available
| |
| | respiratory arrest, or worsening of COPD
|
| medication for prevention or treatment of
| |
| | [chronic obstructive pulmonary disease]
|
| bird flu, and its use in this situation
| |
| | accompanied by pulmonary edema [water in
|
| is recommended by the Centers for Disease
| |
| | the lungs], after zanamivir inhalation,
|
| Control (CDC) and the World Health
| |
| | particularly in persons with underlying
|
| Organization (WHO).
| |
| | airway disease [such as asthma].
|
| 2. Mechanism of action: neuraminidase
| |
| | Apparent declines in respiratory function
|
| inhibitor (active against all nine
| |
| | have also been rarely reported in those
|
| influenza A neuraminidase subtypes
| |
| | without recognized airway disease.
|
| recognized in nature, including recent
| |
| | Consequently, use in patients with
|
| pathogenic avian viruses [H5N1, H7N7,
| |
| | underlying airway disease is not
|
| N9N2], as well as a virus containing the
| |
| | generally recommended in the United
|
| neuraminidase from the 1918 pandemic
| |
| | States, although treatment in at-risk
|
| strain).
| |
| | patients is used in other countries. If
|
| 3. Available forms: 75 mg capsules and 12
| |
| | used in patients with obstructive airway
|
| mg/ml suspension.
| |
| | disease, zanamivir should be administered
|
| 4. Effective only if given within 48
| |
| | cautiously under close observation and
|
| hours of onset of symptoms.
| |
| | with availability of fast-acting
|
| 5. FDA-approved for treatment for those
| |
| | bronchodilators.
|
| one year and older.a. Dose for treatment
| |
| | 8. Use in pregnancy: Category C (meaning
|
| of influenza for those 12 and older: 75
| |
| | no scientific studies have been done to
|
| mg twice daily for five days.b. Dose for
| |
| | prove that it is safe in
|
| treatment of influenza for those under
| |
| | pregnancy-because of liability, no such
|
| twelve: 2 mg/kg up to a maximum of 75 mg
| |
| | studies are ever undertaken-but available
|
| twice daily for five days.c. Side effects
| |
| | evidence indicates that it is probably
|
| occurring in five percent or more of
| |
| | safe to use during pregnancy).
|
| patients taking Tamiflu for treatment
| |
| | 9. Significant drug interactions: none.
|
| were nausea, vomiting, and diarrhea.
| |
| | How effective is Relenza for prevention
|
| These symptoms generally do not persist
| |
| | or treatment of seasonal influenza?
|
| with ongoing treatment. Rare instances of
| |
| | Clinical studies have shown the
|
| serious side effects have been reported,
| |
| | following:
|
| but they are of uncertain relationship to
| |
| | Early inhaled zanamivir (10 mg twice
|
| Tamiflu.
| |
| | daily for five days) treatment of
|
| 6. FDA-approved for prophylaxis
| |
| | uncomplicated influenza in previously
|
| (prevention) of influenza for those 13
| |
| | healthy adults and children aged five to
|
| and older:a. Dose for prophylaxis of
| |
| | 12 years shortens the time to illness
|
| influenza for those 12 and older: 75 mg
| |
| | resolution and return to usual activities
|
| daily for 10 days.b. Not approved for
| |
| | by one to three days. Treatment benefits
|
| prophylaxis of influenza for those
| |
| | appear to be greater in those with severe
|
| younger than 12. However, use of Tamiflu
| |
| | symptoms at entry, in those older than 50
|
| in this situation is probably safe and
| |
| | years, and in higher-risk patients.
|
| effective. By deduction, dose should be
| |
| | Inhaled zanamivir treatment in adults is
|
| 1 mg/kg up to a maximum of 75 mg daily
| |
| | associated with a 40 percent reduction in
|
| for 10 days.c. Side effects occurring in
| |
| | lower respiratory tract events leading to
|
| five percent or more of patients taking
| |
| | antibiotic use and a 28 percent overall
|
| Tamiflu for prophylaxis were headache,
| |
| | reduction in antibiotic prescriptions. In
|
| nausea, and fatigue.
| |
| | high-risk patients with primarily
|
| 7. Use in pregnancy: Category C (meaning
| |
| | mild-to-moderate asthma or other chronic
|
| no scientific studies have been done to
| |
| | cardiopulmonary conditions, zanamivir
|
| prove that it is safe in
| |
| | treatment reduces illness duration and
|
| pregnancy-because of liability, no such
| |
| | the incidence of complications leading to
|
| studies are ever undertaken-but available
| |
| | antibiotic use.
|
| evidence indicates that it is probably
| |
| | Prophylactic administration of once-daily
|
| safe to use during pregnancy).
| |
| | inhaled zanamivir (10 mg) is protective
|
| 8. Significant drug interactions: none
| |
| | against febrile influenza illness during
|
| (although probenecid doubles the level of
| |
| | influenza season (84 percent efficacy) or
|
| oseltamivir)
| |
| | when used for post-exposure prophylaxis
|
| How effective is Tamiflu for prevention
| |
| | in households with or without treatment
|
| or treatment of seasonal influenza?
| |
| | of the ill index case (82 percent
|
| Clinical studies have shown the
| |
| | efficacy).
|
| following:
| |
| | One study found that two weeks of inhaled
|
| Oral oseltamivir is highly protective
| |
| | zanamivir was superior to oral
|
| against experimental human influenza, and
| |
| | rimantadine [another antiviral drug] in
|
| early treatment is associated with
| |
| | preventing influenza A infection in
|
| reductions in viral titers, symptoms,
| |
| | nursing home residents, in part because
|
| nasal cytokines [inflammatory agents],
| |
| | of a high frequency of rimantadine
|
| and middle-ear pressure abnormalities.
| |
| | resistance, and inhaled zanamivir has
|
| Early oseltamivir treatment of acute
| |
| | been used to curtail transmission of
|
| influenza in otherwise healthy adults and
| |
| | amantadine-resistant influenza A in
|
| children aged one to 12 years reduces the
| |
| | nursing homes. However, inhaled zanamivir
|
| time to illness alleviation by one to 1.5
| |
| | is not approved for chemoprophylaxis
|
| days, fever duration, and viral titers in
| |
| | (prevention) in the United States or most
|
| the upper respiratory tract. Early
| |
| | other countries.
|
| treatment reduces time to functional
| |
| | Finally, it is important to be aware of
|
| recovery by three days or more.
| |
| | the fact that the effectiveness of
|
| Treatment of children also reduces the
| |
| | Tamiflu and Relenza has been studied
|
| risk for otitis media [inner-ear
| |
| | against circulating strains of human
|
| infection] and decreases overall
| |
| | influenza, not against the bird flu
|
| antibiotic use. In healthy and high-risk
| |
| | virus. In a study reported in the August
|
| adults, early treatment decreased the
| |
| | issue of the Journal of Infectious
|
| risk for lower respiratory tract
| |
| | Diseases, Yen and others from St. Jude
|
| complications leading to antibiotics and
| |
| | Children's Research Hospital in Memphis,
|
| to hospitalization. In is unknown
| |
| | Tennessee found that eight-day regimens
|
| whether treatment reduces the risk for
| |
| | of Tamiflu were more effective than the
|
| transmission [of the virus from the
| |
| | suggested five-day regimen for treating
|
| infected person to someone else].
| |
| | infections with the H5N1 bird-flu virus.
|
| Prophylactic administration of once-daily
| |
| | The authors concluded that a prolonged
|
| oral oseltamivir (75 mg) is highly
| |
| | and higher-dose oseltamivir regimen may
|
| effective in reducing the risk for
| |
| | be required for the most beneficial
|
| developing febrile illness during
| |
| | antiviral effect.
|
| influenza season in unimmunized adults.
| |
| | Bradford Frank, M.D., M.P.H., M.B.A.
|
| Prevention of influenza reduces secondary
| |
| | The Frank Group
|
| complications in institutionalized older
| |
| | P.O.
|
