Section 3: Cholinergic agonists/antagonists

Question 1

Name the cholinergic (muscarinic) agonists

Answer 1

Muscarine, ACh, bethanechol, cevimeline, pilocarpine (my mnemonic….Moody Agonizing beth can pee (bethanocol increses urinary contraction-M3) Thanks Laura!

Question 2

Name the cholinergic (muscarinic) antagonists

Answer 2

atropine, ipratropium bromide, scopolamine, tolterodine, tropicamide (my mnemonic….Atropa bellodona IS Totally Tropical)

Question 3

Two enzymes reduce ACh duration of action:

Answer 3

AChE and BCE (butyrylcholinesterasen in the plasma)

Question 4

Topical instillation of ACh has three effects:

Answer 4

miosis (iris spinchter muscle) which is the only remaing clinical use; accomodation (ciliary muscle contracts); ciliary muscle contraction opens pores of trabecular meshwork, + outflow, - IOP

Question 5

A drug which can prevent tachycardia due to ACh

Answer 5

Atropine (M3 antagonist)

Question 6

ACh reduces vascular resistance how?

Answer 6

M3 agonist, vascular endothelium releases NO causing vascular smooth muscle to relax

Question 7

Which heart conditions are treated with atropine?

Answer 7

It’s an M1/M2 antagonist, blocking vagal stimulation of the SA node so it’s good for bradycardia and AV block (cardiac resuscitation)

Question 8

What is bethanocol used for and why is it long acting? It is the prototype of which drug class?

Answer 8

Reduces urinary retention (M3 agonist of detrussor). It resists hydrolysis by cholinesterases. Its the prototype synthetic choline ester.

Question 9

What is the prototype cholinimemtic alkaloid? What effects does it have on the eye?

Answer 9

Pilocarpine is a partial agonist of all M subtypes. In the eye: miosis, accomodates (blurs distance), and - IOP. Used as 2nd line drug tx for wide-angle glaucoma and for xerostomia.

Question 10

Alkaloid that is a selective M3 agonist which is used to treat what? Why is it used instead of pilocarpine?

Answer 10

Cevimeline (has lower affinity for caridac M2). Tx of dry mouth with Sjogrens syndrome (autoimmune M3 degradation). Fewer side effects and longer duration than pilocarpine.

Question 11

*Contraindications for muscarinic agonists?

Answer 11

Hyperthyroidism (SNS already exacerbated so don’t risk reflex tachycardia), asthma (M lung), peptic ulcer (M + secretions)

Question 12

antidotes for muscarinic agonists?

Answer 12

atropine (blocks receptors) and/or epinephrine

Question 13

Therapeutic use of ipratropium BRomide

Answer 13

BRonchodilator approved for COPD, used also for asthma

Question 14

Can be used post-operatively to reduce emesis and nausea.

Answer 14

Scopolamine. Is also used for motion sickness. (I like Molly’s fishing pole image)

Question 15

urge incontinence

Answer 15

Tolterodine

Question 16

used as a mydriatic/cycloplegic

Answer 16

Tropicamide. Dilation and loss of accommodation

Question 17

Muscarinic agonist side-effects/OD

Answer 17

Most commonly sweating, hypotension, cramps, diarrhea

Question 18

Who should be of particular concern with the use of tolterodine? Why?

Answer 18

Tolterodine is a non-selective antagonist used for urge incontinence. Its main problem are CNS anticholinergic effects (drowsiness, dizziness, and confusion) which are particularly detrimental to geriatrics.