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1 23rd January 14:02
deena via medkb.com
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Posts: 1
Default Asthma and Viagra (viagra asthma pulmonary impotence pulmonary edema)


Viagra gets tested for another purpose

OXFORD, England Bob Dole and his contemporaries aren't the only ones
popping little blue pills these days. During a two-month-long trial currently
underway in Bolivia, more than 100 volunteers are participating in tests to
see whether Viagra might be used to prevent and treat illnesses associated
with high altitude.
At high altitudes, the blood vessels in the lungs contract, a phenomenon that
can lead to potentially fatal pulmonary edema, an ac***ulation of fluid that
makes it difficult for the lungs to supply the body with oxygen and eliminate
carbon dioxide.

Viagra came to fame as the first medication to treat male impotence. Altitude
sickness, like male impotence, results when blood vessels are too constricted.
The hope is that by causing blood vessels in the lungs to dilate, Viagra will
aid the transfer of oxygen from the lungs to the bloodstream and thereby
prevent altitude sickness.

"Viagra is very selective in its effects, and it acts on two main parts of
the body. The first is obviously the genitals, but the other is the lungs,"
says project research director Kenneth Baillie from his home in Edinburgh.

If the experiment proves Viagra is effective, it may have implications for
other illnesses and symptoms caused by shortage of oxygen, including asthma.

In order to determine the drug's effectiveness, researchers are using an
ultrasound probe to measure the blood pressure in volunteers' lungs at high
altitude.

The expedition is being organized by Apex, a British medical charity founded
by Baillie and five others when they were still medical students in 2000. The
group of young internal medicine specialists all shared an interest in high
altitude physiology. For this expedition, the volunteers themselves are
paying most of the travel costs; the research costs are being covered by Apex,
with the help of the British Heart Foundation and several other charities.

"It's difficult to study altitude illnesses because of the remote location of
these environments," Baillie says. Advanced experiments require electrical
power and the ability to transport blood samples.

The Apex expedition makes use of the power at the Chacaltaya laboratory
normally a physics lab which is at 17,060 feet. Meanwhile, Marken, a
specialized courier company, will pick up blood samples from the mountaintop
lab and transport them at minus 70 degrees Celsius back to the researchers'
lab in Edinburgh.

The 106 participants, all volunteers, are mostly students from the University
of Edinburgh and other British universities. They are going up to the
mountaintop in groups of 20 to 30, each spending 10 days at the lab.

About half of the volunteers are taking Viagra, the other half are taking a
placebo.

Are the researchers concerned about the possible unintended consequences of
giving Viagra to a test group that includes a large number of 18- to 24-year-
old men? "We worried that the volunteers might be able to tell that they had
the Viagra because of one ... er ... particular side effect," Baillie admits.


However, he adds, "We're hoping that there will be a strong enough placebo
effect that they won't be able to tell."

Roger Thompson, the project director, reports by telephone from Bolivia that
so far the volunteers haven't been able to discern whether they are taking
the drug or the placebo. "We had one guy who thought he was on it for a few
days, but then decided later that he wasn't." In order to make the experiment
legitimate, neither the researchers nor the subjects know who is taking the
drug at this point.

Those who are on the drug are taking a particularly high dosage. "It's about
one and a half times the dose you would take when using Viagra for other
purposes," Thompson says. And the volunteers take it three times a day to
ensure that there is enough of the drug in their blood 24 hours a day.

Richard Oram, 23, is looking forward to his role as one of the research
volunteers. "It's an opportunity to be a part of some really advanced
research," he says.

The Oxford medical student says he doesn't expect any problems with Viagra.
"I've never taken it before, so I'm slightly curious," Oram says. "I expect
I'll know if I'm on it, but then again, *** is such a psychological thing so
the placebo effects should be strong. So who knows?"

As for what his parents might think about the experiment, Oram says, "I
haven't talked to them much about it, but I think they've had a good laugh."

In addition to the lung blood pressure tests, by testing the concentration of
various gases in the subjects' breath while they exercise, researchers hope
to prove that Viagra makes athletic activity at high altitudes easier.

Thompson says that the students have been active during their time at the lab,
some of them making the 1,000-foot climb from the lab to Mount Chacaltaya's
summit several times a day.

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2 23rd January 14:02
00doc
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Posts: 1
Default Asthma and Viagra (asthmatic pulmonary pulmonary edema down heart)


PDE5 inhibitors (PDE5I's like Viagra, Levitra, and Cialis) causes
vasodilation by increasing levels of nitric oxide (not to be confused with
"laughing gas" = nitrous oxide). All blood vessels respond to this but it
turns out that the arteries of the lungs are more sensitive to it (i.e.
respond at lower levels) then the system circulation. This is why people
taking nitrates for their heart cannot take Viagra. It results in life
threateningly low blood pressures.

In an acute attack the lung closes down blood vessels feeding hypoxic
partsof the lungs and preferentially shunts it ot the parts that are still
getting oxygen. So giving a PDE5I to a hypoxic asthmatic in an acute attack
would likely result in shunting of blood away from the ventilated parts of
the lung to unventilated parts and would worsen hypoxia.

In chronically hypoxic pulmonary patients (more often seen in emphysemia and
other chronic lung diseases than asthma) the entire pulmonary circulation
closes down and created high blood pressures in the pulmonary arteries
(pulmonary hypertension) and problems pumping blood for the right side of
the heart (right heart failure). For this the Viagra has been shown to be
beneficial.

My point is that you will see these meds used in certain types of lung
patients more and more but it will only be beneficial for the absolute worst
asthmatics (those so bad they require daily oxygen) and it won't have much
if any role in acute attacks. They probably should have used a different
word than "asthma" in that last sentence.

Altitude sickness is another condition involving hypoxia, pulmonary
hypertension, and vasogenic pulmonary edema (leaky vessels leading to fluid
in the lungs) so there is active research on whether PDE5I's can help.

Of course they are students. Who else would volunteer to spend 10 days in a
lab at the top of a freezing mountain trying to see if they get altitude
sickness? They probably just promised them free pizza.


It is common in placebo controlled studies for the subjects (and sometimes
the researchers) to actively try to thwart the blinding and figure out who
is getting the study drug and who is getting the placebo. Come to think if
it (pun not intended but noted and intentionally not removed) this study
might be more fun than I initially thought.

Like pregnancy?


Why does he think they are signing up? I'm sure the only thing the subjects
are worried about is being in the placebo group.


Advanced what?


And who cares?


No comment.

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00doc
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