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Welcome. My name is Paul Boylan.
I'm an associate professor
in the Department of Pharmacy
at the University of
Oklahoma Health Sciences,
College of Pharmacy,
in Oklahoma City, Oklahoma.
Welcome to Part 3 of
this presentation
on theophylline and
anti-leukotrienes
for the treatment of
airway allergic diseases.
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Part 3 of this presentation
will cover montelukast
and the leukotriene
receptor antagonists
for the treatment of those
airway allergic diseases.
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As you may recall from Part
1 of our presentation,
leukotrienes are compounds
that induce inflammation.
This class of medications are
only administered orally,
and they have various indications
not only to treat lower,
but also upper airway
inflammatory disorders.
I've listed for you
the three most common
leukotriene receptor antagonists
that are available
across the globe.
Those agents include
montelukast,
zafirlukast and zileuton.
You can see that montelukast is
the most common of these agents,
likely because it is
indicated to treat
both asthma and allergies,
technically known as
allergic rhinitis,
and it is indicated for
a wide range of ages.
It may be used in patients
as young as two years of age
and may be used
into adolescence,
as well as into adulthood.
Recently, and we will cover
later in this presentation,
montelukast has
received new warnings
for the potential for
neuropsychiatric events.
Zafirlukast was the leukotriene
receptor antagonist
that anteceded
montelukast on the market
and possesses only the
indication for asthma.
You can see that it has
a smaller range of
ages to be used for,
compared to montelukast.
It should not be
used in patients
less than five years of age.
It perhaps may not be as
common as montelukast
because of its side
effect profile,
and requires one
additional dose per day
compared to montelukast.
That is, zafirlukast is
administered two times per day,
whereas montelukast
has the convenience
of only requiring
once-daily administration.
Whereas montelukast has warnings
for neuropsychiatric events,
zafirlukast has concerns
for causing liver
damage and injury,
and has warnings
for hepatotoxicity.
Zileuton, I should disclose,
is not necessarily
and technically
a leukotriene
receptor antagonist.
Instead, its correct
pharmacologic category
is that of a
5-lipoxygenase inhibitor.
That is, it works more upstream,
as you will recall from
our Part 1 presentation
on immunology and
pathophysiology
and pharmacology.
Because of this, zileuton
should only be used
in adolescents at
least 12 years of age.
It has a higher dose
of 1200 milligrams
and, similar to zafirlukast,
requires twice-daily
administration.
Zileuton is also
metabolized in the liver,
and in its liver metabolism,
it inhibits a very common enzyme
that is responsible
for breaking down
other medications and compounds.
That enzyme is the
cytochrome P450 enzyme,
and the specific
isozyme of CYP450
will be that 1A2 isozyme.
