- Hello Jeff - Most people haven't a clue if they get their
news from network talking head droids. There is a very disturbing situation
that has begun - now H1N1 is resistant to the new antiviral in clinical
trials.
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- Giving antivirals to immune compromised individuals is,
in my opinion, risky because their immune systems don't work properly.
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- Patty
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- Source: PHYSORG.com News
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- Rapid development of drug-resistant 2009 H1N1 influenza
reported in 2 cases
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- Doctors from the National Institute of Allergy and Infectious
Diseases (NIAID) report that 2 people with compromised immune systems who
became ill with [pandemic (H1N1) 2009] influenza [virus infection] developed
drug-resistant strains of virus after less than 2 weeks on therapy. Doctors
who treat prolonged influenza infection should be aware that even a short
course of antiviral treatment may lead to drug-resistant virus, say the
authors, and clinicians should consider this possibility as they develop
initial treatment strategies for their patients who have impaired immune
function.
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- Both patients in the new report developed resistance
to the key influenza drug oseltamivir (Tamiflu), and one also demonstrated
clinical resistance to another antiviral agent, now in experimental testing,
intravenous peramivir, note senior authors Matthew J Memoli, MD, and Jeffery
K Taubenberger, MD, PhD. This is the 1st reported case of clinically significant
peramivir-resistant 2009 H1N1 illness, say the scientists. The report is
scheduled to appear in print on 1 May [2010] in Clinical Infectious Diseases
and is now online [MJ Memoli et al: Rapid selection of oseltamivir and
peramivir resistant pandemic H1N1 during therapy in 2 immunocompromised
hosts. Clinical Infectious Diseases DOI:10. 1086/651605 (2010)]. The people
in the current case report had immune limitations due to blood stem cell
transplants that occurred several years previously. Both recovered from
their influenza infections.
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- "While the emergence of drug-resistant influenza
virus is not in itself surprising, these cases demonstrate that resistant
strains can emerge after only a brief period of drug therapy," says
NIAID Director Anthony S Fauci, MD. "We have a limited number of drugs
available for treating influenza and these findings provide additional
urgency to efforts to develop antivirals that attack influenza virus in
novel ways."
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- The pandemic (H1N1) 2009 influenza virus is susceptible
to just one of the 2 available classes of anti-influenza drugs, the neuraminidase
inhibitors. Besides oseltamivir, other neuraminidase inhibitors are zanamivir
(Relenza), which is inhaled, and the intravenously administered investigational
drug peramivir. As the H1N1 influenza pandemic unfolded, laboratory tests
of virus strains isolated from patients showed that some strains contained
a genetic mutation (the H275Y mutation) that makes the virus less susceptible
to some neuraminidase inhibitors.
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- The 2 people in the current case study had pre-existing
medical conditions that impaired their immune system function before contracting
2009 H1N1 flu. Strains of pandemic (H1N1) 2009 virus containing the H275Y
mutation had been reported previously in people with diminished immune
function, but in previous cases the mutation arose after more than 24 days
of continuous therapy. In the newly described cases, the mutation appeared
after 14 days in one individual and after 9 days in the 2nd. "Although
the recommended length of treatment with oseltamivir is 5 days, it is common
for physicians to continue giving this 1st-line drug longer if the patient
does not improve," says Dr Memoli.
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- Both people in the current report received oseltamivir
for extended periods but they continued to shed virus in their nasal secretions
throughout treatment. When one patient's condition worsened despite 24
days of oseltamivir treatment, doctors administered peramivir for 10 days.
The drug did not reduce viral shedding and the patient remained ill, demonstrating
what the authors described as clinically significant resistance to peramivir.
Next, doctors administered the only other available flu drug, zanamivir,
for 10 days. The person then fully recovered.
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- "Additional, larger studies are needed to further
refine our findings," says Dr Memoli. "But these cases of rapid
appearance of drug-resistant 2009 H1N1 influenza in immune-compromised
patients are worrisome and should prompt clinicians to reconsider how they
use available flu drugs."
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- The mutation that allows the pandemic (H1N1) 2009 influenza
virus to resist oseltamivir also significantly reduces the virus's susceptibility
to peramivir. If a relatively short course of oseltamivir causes a mutant
flu strain to emerge in a particular patient, that person may not respond
to peramivir. Zanamivir might be a good choice if a patient does not respond
within a few days to oseltamivir, Dr Memoli says. However, because zanamivir
must be inhaled, patients who are very ill and whose breathing is mechanically
supported cannot be given zanamivir.
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- "As clinicians, we should carefully consider our
treatment options and use all the drugs available to us wisely. This is
especially important in a patient with prolonged infection or when an antiviral
drug fails to cure the patient after the recommended course of treatment,"
says Dr Memoli.
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- http://www.physorg.com/news188830290.html
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- --
- Communicated by
- ProMED-mail
- promed@promedmail.org
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- Previously it was reported that a kidney transplant patient
in Western Australia developed resistance to oseltamivir and ultimately
the patient's infection was cleared by zanamivir treatment (Medical Journal
of Australia, 11 Jan 2010... http://www.mja.com.au/public/issues/192_03_010210/spe11148_fm.html
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- Although both oseltamivir and zanamivir are inhibitors
of the activity of the influenza virus neuraminidase protein, the oseltamivir-resistance
(His274Tyr) mutation does not confer resistance to zanamivir. The interesting
feature of the NIAID report is the rapidity of appearance of oseltamivir
resistance and the lack of response to another antiviral agent, now in
experimental testing, intravenous peramivir, which presumably has the same
site of action as oseltamivir.
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- One patient's infection was ultimately cleared by zanamivir
treatment. It is not recorded if the patient's virus remained zanamivir
sensitive. - Mod.CP]
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- Patricia A. Doyle DVM, PhD Bus Admin, Tropical Agricultural
Economics Univ of West Indies Please visit my "Emerging Diseases"
message board at:http://www.emergingdisease.org/phpbb/index.php Also
my new website: http://drpdoyle.tripod.com/ Zhan le Devlesa tai
sastimasa Go with God and in Good Health
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