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HMC Main Pharmacy has the responsibility for distributing the antiviral drugs to all the screening points that offer treatment as well as assessment. It is the responsibility of the screening points to ensure compliance with the indication and criteria for the use of the antiviral drugs. The practice will be subject to auditing and monitoring.
Confirmed, Probable and Suspected
Cases of Swine-origin Influenza A
(H1N1) Virus Infection
Recommendations for use of
antivirals may change as data on
antiviral effectiveness, clinical
spectrum of illness, adverse events
from antiviral use, and antiviral
susceptibility data become
available.
Antiviral treatment should be
considered for confirmed, probable
or suspected cases of swine-origin
influenza A (H1N1) virus infection.
Treatment of hospitalized patients
and patients at higher risk for
influenza complications should be
prioritized.
Only RT-PCR or viral culture can
confirm infection with swine-origin
influenza A (H1N1) virus. The test
performance of rapid antigen tests
and immunofluorescence tests for
detection of swine-origin influenza
A (H1N1) virus is unknown. Persons
who might have swine-origin
influenza A (H1N1) virus and who
test positive for influenza A using
one of these tests should have
confirmatory RT-PCR or viral culture
testing to confirm the presence of
swine-origin influenza A (H1N1)
virus. A negative rapid antigen or
immunofluorescence test cannot be
used to rule out swine-origin
influenza A (H1N1) virus infection.
Antiviral treatment with zanamivir
or oseltamivir should be initiated
as soon as possible after the onset
of symptoms. Evidence for benefits
from treatment in studies of
seasonal influenza is strongest when
treatment is started within 48 hours
of illness onset. However, some
studies of treatment of seasonal
influenza have indicated benefit,
including reductions in mortality or
duration of hospitalization even for
patients whose treatment was started
more than 48 hours after illness
onset. Recommended duration of
treatment is five days.
Recommendations for use of
antivirals may change as data on
antiviral susceptibilities and
effectiveness become available.
Antiviral doses recommended for
treatment of swine-origin influenza
A (H1N1) virus infection in adults
or children 1 year of age or older
are the same as those recommended
for seasonal influenza. Oseltamivir
use for children < 1 year old was
recently approved by the U.S. Food
and Drug Administration (FDA) under
an Emergency Use Authorization (EUA),
and dosing for these children is
age-based.
Note: Areas that continue to have
seasonal influenza activity,
especially those with circulation of
oseltamivir-resistant human A (H1N1)
viruses, might prefer to use either
zanamivir or a combination of
oseltamivir and rimantadine or
amantadine to provide adequate
empiric treatment or
chemoprophylaxis for patients who
might have human influenza A (H1N1)
infection.
Antiviral Chemoprophylaxis
For antiviral chemoprophylaxis of
swine-origin influenza A (H1N1)
virus infection, either oseltamivir
or zanamivir are recommended.
Duration of antiviral
chemoprophylaxis post-exposure is 10
days after the last known exposure
to an ill confirmed case of
swine-origin influenza A (H1N1)
virus infection. Post exposure
prophylaxis should be considered for
contact during the infectious period
(e.g., one day before until 7 days
after the case’s onset of illness).
If the contact occurred more than 7
days earlier, then prophylaxis is
not necessary. For pre-exposure
protection, chemoprophylaxis should
be given during the potential
exposure period and continued for 10
days after the last known exposure
to an ill confirmed case of
swine-origin influenza A (H1N1)
virus infection. Oseltamivir can
also be used for chemoprophylaxis
under the EUA.
Antiviral chemoprophylaxis with
either oseltamivir or zanamivir can
be considered for the following:
1. Household close contacts who are
at high-risk for complications of
influenza (e.g., persons with
certain chronic medical conditions,
persons 65 years or older, children
younger than 5 years old, and
pregnant women) of a suspected case.
2. Children attending school or
daycare who are at high-risk for
complications of influenza (children
with certain chronic medical
conditions) and who had close
contact (face-to-face) with a
confirmed, probable, or suspected
case.
3. Health care workers who are at
high-risk for complications of
influenza (e.g., persons with
certain chronic medical conditions,
persons 65 or older, and pregnant
women) who are working in an area of
the healthcare facility that
contains patients with confirmed
swine-origin influenza A (H1N1)
cases, or who is caring for patients
with any acute febrile respiratory
illness.
4. Travelers to Mexico who are at
high-risk for complications of
influenza (e.g., persons with
certain chronic medical conditions,
persons 65 or older, children
younger than 5 years old, and
pregnant women).
5. First responders who are at
high-risk for complications of
influenza (e.g., persons with
certain chronic medical conditions,
persons 65 or older, children
younger than 5 years old, and
pregnant women) and who are working
in areas with confirmed cases of
swine-origin influenza A (H1N1)
virus infection.
Side effects of Antivirals
treatment
Oseltamivir
Nausea and vomiting were reported
more frequently among adults
receiving oseltamivir for treatment
(nausea without vomiting,
approximately 10%; vomiting,
approximately 9%) than among persons
receiving placebo (nausea without
vomiting, approximately 6%;
vomiting, approximately 3%). Among
children treated with oseltamivir,
14% had vomiting, compared with 8.5%
of placebo recipients. Overall, 1%
discontinued the drug secondary to
this side effect, and a limited
number of adults who were enrolled
in clinical treatment trials of
oseltamivir discontinued treatment
because of these symptoms. Similar
types and rates of adverse events
were reported in studies of
oseltamivir chemoprophylaxis. Nausea
and vomiting might be less severe if
oseltamivir is taken with food. No
published studies have assessed
whether oseltamivir impairs the
immunologic response to TIV.
Transient neuropsychiatric events
(self-injury or delirium) have been
reported postmarketing among persons
taking oseltamivir; the majority of
reports were among adolescents and
adults living in Japan. FDA advises
that persons receiving oseltamivir
be monitored closely for abnormal
behavior.
Zanamivir
Limited data are available about the
safety or efficacy of zanamivir for
persons with underlying respiratory
disease or for persons with
complications of acute influenza,
and zanamivir is licensed only for
use in persons without underlying
respiratory or cardiac disease. In a
study of zanamivir treatment of ILI
among persons with asthma or chronic
obstructive pulmonary disease in
which study medication was
administered after use of a
B2-agonist, 13% of patients
receiving zanamivir and 14% of
patients who received placebo
(inhaled powdered lactose vehicle)
experienced a greater than 20%
decline in forced expiratory volume
in 1 second (FEV1) after treatment.
However, in a phase-I study of
persons with mild or moderate asthma
who did not have ILI, one of 13
patients experienced bronchospasm
after administration of zanamivir.
In addition, during postmarketing
surveillance, cases of respiratory
function deterioration after
inhalation of zanamivir have been
reported. Because of the risk for
serious adverse events and because
efficacy has not been demonstrated
among this population, zanamivir is
not recommended for treatment for
patients with underlying airway
disease. Allergic reactions,
including oropharyngeal or facial
edema, also have been reported
during postmarketing surveillance.
In clinical treatment studies of
persons with uncomplicated
influenza, the frequencies of
adverse events were similar for
persons receiving inhaled zanamivir
and for those receiving placebo
(i.e., inhaled lactose vehicle
alone). The most common adverse
events reported by both groups were
diarrhea, nausea, sinusitis, nasal
signs and symptoms, bronchitis,
cough, headache, dizziness, and ear,
nose, and throat infections. Each of
these symptoms was reported by less
than 5% of persons in the clinical
treatment studies combined.
Zanamivir does not impair the
immunologic response to TIV.
Use during pregnancy
Oseltamivir, zanamivir, amantadine
and rimantadine are both "Pregnancy
Category C" medications, indicating
that no clinical studies have been
conducted to assess the safety of
these medications for pregnant
women. Only two cases of amantadine
use for severe influenza illness
during the third trimester have been
reported. However, both amantadine
and rimantadine have been
demonstrated in animal studies to be
teratogenic and embryotoxic when
administered at substantially high
doses. Because of the unknown
effects of influenza antiviral drugs
on pregnant women and their fetuses,
these four drugs should be used
during pregnancy only if the
potential benefit justifies the
potential risk to the embryo or
fetus; the manufacturers' package
inserts should be consulted.
However, no adverse effects have
been reported among women who
received oseltamivir or zanamivir
during pregnancy or among infants
born to such women.
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