Cholinergic Antagonists

Question 1

List the 6 tertiary amine cholinergic receptor-inhibitors. Do they block nicotinic or muscarinic receptors?

Answer 1

Atropine, tropicamide, scopolamine, dicyclomine, tolterodine, and benzotropine; block muscarinic receptors

Question 2

List the 2 quaternary amines. Do they block nicotinic or muscarinic receptors?

Answer 2

Ipratropium and tiotropium; block muscarinic receptors

Question 3

In general, are tertiary amines or quaternary amines more readily absorbed and able to cross the BBB?

Answer 3

Tertiary amines are better for both

Question 4

Which 2 tertiary amines are used to cause mydriasis (pupil dilation) and cycloplegia (ciliary muscle paralysis)? Which has the shorter half life?

Answer 4

Atropine and tropicamide; tropicamide has a very short half life

Question 5

Which tertiary amine is used to treat Parkinson’s?

Answer 5

Benzotropine

Question 6

What is the tertiary amine scopolamine most commonly used to treat?

Answer 6

Motion sickness

Question 7

What is the tertiary amine dicyclomine most commonly used to treat?

Answer 7

transient GI hypermotility

Question 8

What tertiary amine is commonly used to treat transient cystitis, postoperative bladder spasms, or incontinence?

Answer 8

Tolterodine

Question 9

The quaternary amines ipratropium and tiotropium are used for what purpose on patients with what 2 diseases? Which drug has a longer half life?

Answer 9

Bronchodilation for asthma and COPD patients; tiotropium is longer acting (1-2 days half life)

Question 10

List 4 common side effects of muscarinic receptor inhibitors.

Answer 10

“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

Question 11

List the 5 miscellaneous cholinergic antagonists, which do not act on muscarinic receptors.

Answer 11

Hexamethonium, succinylcholine, tubocurarine, mivacurium, and botulinum toxin A

Question 12

What cholinergic receptor inhibitor is a pure ganglionic blocker that inhibits Nn receptors at both sympathetic and parasympathetic ganglia?

Answer 12

Hexamethonium

Question 13

What cholinergic receptor inhibitor is a depolarizing blocker? How does it inhibit ACh action?

Answer 13

Succinylcholine; overstimulates the Nm receptor to cause desensitization

Question 14

What 2 cholinergic receptor inhibitors are nondepolarizing blockers of the Nm receptor? Which has the longer half life?

Answer 14

Tubocurarine and mivacurium; tubocurarine (has a half life of 30-60 minutes while mivacurium is rapidly hydrolyzed)

Question 15

What cholinergic receptor degrades SNAP-25, thereby blocking vesicle fusion and ACh release at presynaptic nerve terminals?

Answer 15

Botulinum toxin A

Question 16

Although hexamethonium is rarely used, give 2 instances when it might come in handy.

Answer 16

To treat a hypertensive crisis or to carry out “bloodless field” surgery

Question 17

What is the most noticeable systemic effect of ganglionic blockers such as hexamethonium?

Answer 17

Reduced blood pressure (due to loss of vasoconstriction signals)

Question 18

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?

Answer 18

Atropine fever

Question 19

What 3 cholinergic receptor inhibitors can act as muscle relaxants for procedures not requiring deep anesthesia? Which one is the fastest acting?

Answer 19

Succinylcholine, tubocurarine, and mivacurium; succinylcholine can produce flaccid paralysis within 1 minute

Question 20

What cholinergic antagonist can be used to treat achalasia, strabismus, and oromandibular dystonia?

Answer 20

Botulinum toxin A

Question 21

Besides disturbance of autonomic functions, what is a possible side effect of using the Nm receptor (NMJ junction) blockers?

Answer 21

Respiratory paralysis

Question 22

Which 2 drugs are used to treat acute poisoning with an AChE inhibitor (such as organophosphates)?

Answer 22

Atropine and pralidoxime

Question 23

Name the only drug that targets and blocks the Nn receptor.

Answer 23

Hexamethonium