Study Set Content:
All ganglion-blocking drugs of interest are
synthetic
amines.
the first to be recognized as having this action, has
a very short duration of action.
TETRAETHYLAMMONIUM (TEA)
was developed and was introduced clinically as
the first drug effective for management of
hypertension
NEXAMETHONIUM ("C6")
There is an obvious relationship between the
structures of the agonist acetylcholine and the
nicot antagonists
tetracthylammonium and
hexamethonium.
the "C10" analog of hexamethonium, is a
depolarizing neuromuscular blocking agent.
DECAMETHONIUM
a secondary amine, was developed to improve the
degree and extent of absorptie from the
gastrointestinal tract because the quaternary
amine ganglion-blocking compounds were poorly
and erratically absorbed after oral administration.
MECAMYLAMINE,
a short-acting ganglion blocker, is inactive orally
and is given by intravenous infusion
TRIMETHAPHAN
compete with acetylcholine to
bind with nicotinic receptors of both parasympathetic &
sympathetic ganglia.
Ganglionic inhibitors
(if amplified with a cholinesterase inhibitor) can
produce depolarizing ganglion block.
Nicotine, carbamoylcholine, and even acetylcholine
Drugs now used as ganglion blockers are classified
as nondepolarizing competitive antagonists.
Blockade can be surmounted by increasing the
concentration of an
agonist, eg. acetylcholine.
hexamethonium actually produces most
of its blockade by occupying sites in or on the
(blank), not by occupying the
cholinoceptor itself.
nicotinic ion channel
unlike the quaternary amine agents
and trimethaphan, crosses the blood-brain barrier and
readily enters the CNS.
Mecamylamine,
(blank)
(repetitive and rapid, jerky, involuntary
movement), and mental aberrations have been
reported as effects of Mecamylamine,
Sedation, tremor, choreiform movements
The ganglion-blocking drugs cause a predictable
cycloplegia with loss of accommodation because the
ciliary muscle receives innervation primarily from
parasympathetic nervous system.
The effect on the pupil is not so easily predicted,
since the iris receives both
sympathetic
innervation (mediating pupillary dilation) and
parasympathetic innervation
Ganglionic blockade often causes (blank) of the pupil because parasympathetic
tone usually dominates this tissue.
moderate
dilation
Blood vessels receive chiefly (blank) from the sympathetic nervous system;
vasoconstrictor fibers
Therefore, ganglionic blockade causes a marked
decrease in
arteriolar and venomotor tone.
is especially marked in the upright
position (orthostatic or postural hypotension), because postural reflexes that normally prevent
venous pooling are blocked.
Hypotension
Cardiac effects include diminished (blank)
and, because the sinoatrial node is usually
dorpinated by the parasympathetic nervous
system, a moderate (blank)
contractility, tachycardia.
