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Astemizole

Astemizole is a synthetic antihistamine that acts as a selective antagonist of the histamine H1 receptor. It was developed by Janssen and marketed as a long-acting, relatively non-sedating antihistamine for allergic rhinitis and chronic urticaria. It gained widespread use in the 1980s and 1990s but was withdrawn from many markets after safety concerns emerged.

Pharmacology: It binds to H1 receptors to reduce histamine-mediated symptoms. The compound is highly lipophilic with

Safety and regulation: Astemizole can prolong the QT interval by blocking cardiac IKr potassium channels, increasing

Current status: Astemizole is not approved for medical use in most countries. It is discussed in pharmacology

a
long
half-life.
It
is
extensively
metabolized
in
the
liver
by
cytochrome
P450
3A4
to
inactive
metabolites.
Plasma
levels
can
be
markedly
increased
by
inhibitors
of
CYP3A4
such
as
macrolide
antibiotics
and
azole
antifungals,
leading
to
greater
risk
of
adverse
effects.
the
risk
of
torsades
de
pointes
and
sudden
death,
particularly
in
patients
with
electrolyte
disturbances
or
congenital
long
QT
syndrome,
and
when
taken
with
other
QT-prolonging
drugs.
In
the
late
1990s,
safety
concerns
prompted
regulatory
actions
and
withdrawal
from
the
U.S.
market
and
many
others;
it
has
since
been
replaced
by
safer
antihistamines
such
as
cetirizine
and
loratadine.
and
drug-safety
histories
as
an
example
of
a
drug
withdrawn
because
of
cardiac
safety
risks.