Cholinergic Antagonists

Question 1

What is the prototype drug of the antimuscarinic/anticholinergic drugs?

Answer 1

Atropine! Could also say Scopalomine.

Question 2

Compare atropine and scopolamine and their CNS entry

Answer 2

Atropine - enter CNS only at high doses

Scopolamine - enters CNS easily

Question 3

Name effects of Atropine

Answer 3

Blocks msucarinic receptors
Depends on prevailing tone to start with.
Salivary, sweat, bronchioles all affected at [low]
Heart, eye
GI and GU at higher [ ]

only see CNS effects with very high doses

Question 4

Explain what a muscarinic antagonist does to the eye

Answer 4

Think:
muscarinic antagonist will inhib PSNS action
Pupil will dilate (mydriasis)
Angle will decrease
Lens flattens –> sight affected
Eyes will be dry due to inhibited lacrimation.

Question 5

Name a muscarinic antagonist with the shortest duration of action that is used on the eye?

Answer 5

Tropicamide - 6hrs of effect

Question 6

Explain the role PSNS has on Sympathetics at the heart with respect to M2 receptors.

Answer 6

PSNS release Ach that will bind M2 and inhibit cAMP
NE release is decreased
K channels are opened –> hyperpolarization

Question 7

Explain what a muscarinic antagonist could do to the heart.

Answer 7

Removes the direct effect of PSNS, so increases NE release and increases HR.

Question 8

Explain Atropine’s effects on HR and BP.

Answer 8

low does: atropine will decrease HR
increased Ach release –> removes blockade of ACh
release by presynaptic M2 receptors
high dose: atropine will increase HR

NO EFFECT ON BP

Question 9

Compare atropine’s effect on CV between young and old patients.

Answer 9

Young patient with lower resting HR (high vagal tone)
will see tachycardia

Older patient or BABY with higher resting HR (low vagal)
small CV effect

Question 10

Name a drug that can be used to prevent vagal firing during surgery?

Answer 10

Glycopyrrolate

Question 11

Why does atropine not have an effect on BV?

Answer 11

NO PSNS innervation to BV

when atropine O.D. –> see vasodilation in response to decrease the heat from increased body temp

Question 12

What cholinergic antagonists act in the lungs locally?

Answer 12

“=tropiums”
ex: tiotropium

Acute Asthma or COPD
Can reverse bronchoconstriction

Question 13

Give an example of cholinergic antagonist that works in the GI system?

Answer 13

Dicyclomine - antispasmodic

often give to those with IBS
Dominant tone in GI is PSNS

Question 14

Name the classes of cholinergic antagonists that work in the bladder?

Answer 14

“-terodine” and “-fenacin”

NO CNS EFFECTS!
decrease bladder motility - helpful with overactive bladder
Ex: tolterodine

Question 15

What is one problem of giving Tolterodine to men with BPH?

Answer 15

Exaccerbates urinary retention.

Question 16

What is one danger of giving Tropicamide in the eye?

Answer 16

If pt has high intraoccular pressure due to glaucoma, can further narrow the angle!

Question 17

Atropine can be used to decrease what heart rate phenomenon?

Answer 17

Atropine will decrease bradycardia
(think: muscarininc antagonist –> muscarinic would usually decrease heart)

give after MI

Question 18

Name some side effects from “-terodines” and “-fenacines”

Answer 18

used for over active bladder treatment

since M3 antagonist –> can get side effects:
dry mouth
glaucoma
blurred vision

Question 19

Name one over active bladder drug that has pharmacokinetic interactions?

Answer 19

Darifenacin
(Enablex)

“enables you to have big probs with other meds”

Question 20

Name a good choice for post-surgery bladder issues?

Answer 20

Trospium
patch, keeps [ ] low and steady
less side effects
decreases bladder tone which can spasm post-op

Question 21

Name a few side effects of scopolamine

Answer 21

Sedation
short term memory loss
euphoria if abused
toxicity has CNS effects

Question 22

Common side effects of a cholinergic antagonist?

Answer 22

Dry mouth
Decreased bronchial secretions
Tachycardia (dependent on existing tone)
Mydriasis
Decreased GI motility 
Urinary retention (older men)
Dry skin, decreased sweat

Question 23

2 diseases that are contraindicated for cholinergic antagonist?

Answer 23

GLAUCOMA

BPH!

Question 24

Colloquial description of an atropine O.D?

Answer 24

Dry as a bone
Blind as a bat
Red as a beet.
Mad as a hatter.

Question 25

What is the treatment for an atropine overdose?

Answer 25

Supportive treatment

PHYSIOSTIGMINE! (AChE inhibitor)
It has CNS effects - which we want here!

reasoning: atropine is a cholinergic antagonist
physiostigmine will leave ACh in the cleft longer
Eventually, it will be able to act
Also - has CNS effects

Question 26

What is the treatment for cholinergic agonist or AChE inhibitory toxicity?

Answer 26

Inject atropine until pupils dialate and mouth is dry