For Miranda Knowlton, 32, holiday
shopping is truly scary. Miranda's been keeping her asthma
under control with beta agonists and by avoiding triggers
-- like strong perfume. Last December, as she was
rushing through the cosmetics department, she ran into
a cloud of heavy, musky scents. The Yves St Laurent and
Channel sales clerks were in a heated battle with perfume
bottles at full blast, and Miranda was caught in the crossfire.
The result -- a major asthma attack. Unfortunately,
the beta agonists didn't seem all that effective in re-opening
her constricted airways. The reason why may be found in
a pair of recent studies.
The articles, authored by Stanford
University's Dr Shelley Salpeter, indicate that the
drugs themselves could be setting up patients for more
asthma woes and perhaps even heart trouble.
The first study published in the
May issue of Annals of Internal Medicine, looked
at over a dozen papers on the effects of beta agonists
on respiration, and concluded that patients can develop
a tolerance for beta agonists that increases the risk
of asthma attacks. The second study in the June issue
of Chest, examined 33 papers on the cardiovascular
influences of the drugs, and deduced that beta agonists
more than double the risk of heart trouble.
The finding that some industry-funded
studies allowed patients in placebo groups to take beta
agonists 'as-needed,' led researchers to speculate that
these 'flawed' studies may put an artificially positive
spin on the drugs. When only carefully placebo-controlled
studies were considered,"patients on beta agonists started
getting worse asthma symptoms and more frequent respiratory
exacerbations," says Dr Salpeter.
As an emergency response, beta
agonists can be lifesavers. The problem may come when
these drugs are used everyday, creating a higher tolerance
that makes them less effective in the case of a real
emergency.
But as the Chest paper shows,
tolerance is not the only problem with beta agonists.
The doubled risk of heart trouble in beta-agonist users
compared to placebo users is probably because the drugs
bump up the heart rate and cut down on potassium levels,
whereas drugs used to treat heart disease do just the
opposite.
"If you want to push continuous
use of beta agonists, you'll find plenty of published
studies to back your view. However, because of their
flawed designs, none of these trials were placebo-controlled
and therefore should not be used to make valid conclusions
about the safety of beta agonists," says Dr Salpeter.
She also expresses her concern "that physicians who
recommend regular usage of the drugs may actually be
putting their patients at risk."
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