Study Set Content:
are minimally sedating, they are essentially
free of the anticholinergic effects that complicate the use of 1
st
generation. They have a few significant drug-drug interaction and
require less frequent dosing as compared to 1
st generation.
2nd generation H1 blockers
are also more likely to block autonomic
receptors.
first-generation agents
These groups are distinguished by the relatively strong sedative
effects of most of the
first-generation drugs.
are less sedating, owing in part to
their less complete distribution into the central nervous system.
Second-generation H1 blockers
These agents are rapidly absorbed after oral administration, with
peak blood concentrations occurring in
1-2 hours
These agents are rapidly absorbed after oral administration, with
peak blood concentrations occurring in 1-2 hours. They are widely
distributed throughout the body, and the first-generation drugs
enter the (blank) readily
central nervous system
Several of the second-generation agents are metabolized by the
(blank) system and thus are subject to important interactions
when other drugs (such as ketoconazole) inhibit this subtype of
P450 enzymes.
CYP3A4
Many H1 antagonists have
active metabolites
metabolites.The active metabolites
of hydroxyzine, terfenadine, and loratadine are available as
drugs
hydroxyzine, metabolite
(cetirizine,
terfenadine,
fexofenadine,
loratadine
desloratadine,
Both neutral H1 antagonists and inverse H1 agonists reduce or
block the actions of histamine by (blank) to
the H1 receptor.
reversible competitive binding
Several have been clearly shown to be(blank), and it is possible that all act by this mechanism.
inverse
agonists
Both neutral H1 antagonists and inverse H1 agonists reduce or
block the actions of histamine by reversible competitive binding to
the H1 receptor. Several have been clearly shown to be inverse
agonists, and it is possible that all act by this mechanism.
They have negligible potency at the
H2 receptor
Both neutral H1 antagonists and inverse H1 agonists reduce or
block the actions of histamine by reversible competitive binding to
the H1 receptor. Several have been clearly shown to be inverse
agonists, and it is possible that all act by this mechanism.
They have negligible potency at the H2 receptor and little at the
H3
receptor.
For example, histamine-induced contraction of bronchiolar or
gastrointestinal smooth muscle can be completely blocked by these
agents, but histamine-stimulated gastric acid secretion and the
stimulation of the heart are
unaffected
A common effect of first-generation H1 antagonists.
SEDATION
The effect is sufficiently prominent with some agents to
make them useful as (blank) and unsuitable for
daytime use.
"sleep aids"
The effect resembles that of some (blank) drugs
and is considered very different from the disinhibited
sedation produced by sedative hypnotic drugs.
antimuscarinic
