Cholinergic Antagonists Flashcards
List the 6 tertiary amine cholinergic receptor-inhibitors. Do they block nicotinic or muscarinic receptors?
Atropine, tropicamide, scopolamine, dicyclomine, tolterodine, and benzotropine; block muscarinic receptors
List the 2 quaternary amines. Do they block nicotinic or muscarinic receptors?
Ipratropium and tiotropium; block muscarinic receptors
In general, are tertiary amines or quaternary amines more readily absorbed and able to cross the BBB?
Tertiary amines are better for both
Which 2 tertiary amines are used to cause mydriasis (pupil dilation) and cycloplegia (ciliary muscle paralysis)? Which has the shorter half life?
Atropine and tropicamide; tropicamide has a very short half life
Which tertiary amine is used to treat Parkinson’s?
Benzotropine
What is the tertiary amine scopolamine most commonly used to treat?
Motion sickness
What is the tertiary amine dicyclomine most commonly used to treat?
transient GI hypermotility
What tertiary amine is commonly used to treat transient cystitis, postoperative bladder spasms, or incontinence?
Tolterodine
The quaternary amines ipratropium and tiotropium are used for what purpose on patients with what 2 diseases? Which drug has a longer half life?
Bronchodilation for asthma and COPD patients; tiotropium is longer acting (1-2 days half life)
List 4 common side effects of muscarinic receptor inhibitors.
“dry as a bone, blind as a bat, red as a beet, mad as a hatter” - loss of salivation/sweating/lacrimation, loss of accommodation + pupil dilation, flush due to vasodilation, and CNS inhibition
List the 5 miscellaneous cholinergic antagonists, which do not act on muscarinic receptors.
Hexamethonium, succinylcholine, tubocurarine, mivacurium, and botulinum toxin A
What cholinergic receptor inhibitor is a pure ganglionic blocker that inhibits Nn receptors at both sympathetic and parasympathetic ganglia?
Hexamethonium
What cholinergic receptor inhibitor is a depolarizing blocker? How does it inhibit ACh action?
Succinylcholine; overstimulates the Nm receptor to cause desensitization
What 2 cholinergic receptor inhibitors are nondepolarizing blockers of the Nm receptor? Which has the longer half life?
Tubocurarine and mivacurium; tubocurarine (has a half life of 30-60 minutes while mivacurium is rapidly hydrolyzed)
What cholinergic receptor degrades SNAP-25, thereby blocking vesicle fusion and ACh release at presynaptic nerve terminals?
Botulinum toxin A
Although hexamethonium is rarely used, give 2 instances when it might come in handy.
To treat a hypertensive crisis or to carry out “bloodless field” surgery
What is the most noticeable systemic effect of ganglionic blockers such as hexamethonium?
Reduced blood pressure (due to loss of vasoconstriction signals)
What term is given to the potentially lethal hyperthermia which can result from the blockade of sympathetic (but cholinergic/muscarinic) sweat gland innervation in children?
Atropine fever
What 3 cholinergic receptor inhibitors can act as muscle relaxants for procedures not requiring deep anesthesia? Which one is the fastest acting?
Succinylcholine, tubocurarine, and mivacurium; succinylcholine can produce flaccid paralysis within 1 minute
What cholinergic antagonist can be used to treat achalasia, strabismus, and oromandibular dystonia?
Botulinum toxin A
Besides disturbance of autonomic functions, what is a possible side effect of using the Nm receptor (NMJ junction) blockers?
Respiratory paralysis
Which 2 drugs are used to treat acute poisoning with an AChE inhibitor (such as organophosphates)?
Atropine and pralidoxime
Name the only drug that targets and blocks the Nn receptor.
Hexamethonium
