Muscarinic Agonists (Parasympathomimetic Agents)

Question 1

What forms of muscarinic agonists are available?

Answer 1

quaternary nitrogen analogs (structurally derived analogs of ACh–ACh interacts with the muscarinic R with a tight fit) and naturally occurring tertiary amine alkaloids and synthetic analogs

Question 2

What are the four QUATERNARY nitrogen analogs?

Answer 2

1. Acetycholine (prototype compound)
2. Methacholine
3. Carbachol
4. Bethanechol

Question 3

ACh

Answer 3

• binds to both nick and musky R of the ANS, CNS, and NMJ

- rapidly hydrolyzed by AChE and plasmaChE=no therapeutic use

Question 4

METHACHOLINE

Answer 4

• hydrolyzed by AChE, BUT slowered down, so longer duration of action
• primarily musky on smooth mu, glands, and the heart
• Use: dx bronchial hyperactivity in pts suspected of having asthma
• toxicity: bronchiolar constriction
• Ci: pts given beta blockers

Question 5

CARBACHOL

Answer 5

• MORE resistance to hydrolysis by AChE
• stim nick and nusky R
• main use: miotic agent in ophtho (contraction of the pupil)

Question 6

BETHANECHOL

Answer 6

• selective action on musky R of GI tract and urinary bladder
• treats postoperative non-obstructive urinary retention, post partum urinary retention, and neurogenic atony of the bladder
• less side effects that carbachol because less musky TWO R activity (expressed in heart)..BUT can still cause bradycardia
• Ci in: peptic ulcer, asthma, and bradycardia

Question 7

What is a naturally occuring tertiary amines?

Answer 7

PILOCARPINE

Question 8

Why are is the charge of tertiary amines important?

Answer 8

It determines if the compound can cross the BBB.

Question 9

MUSCARINE

Answer 9

• muscarinic poisoning with the ingestion of certain mushrooms
• no clinical utility

Question 10

**What does muscarinic poising cause?

Answer 10

Profound PS activation, and is treated with ATROPINE, a muscarinic receptor ANTagonist

Question 11

**PILOCARPINE

Answer 11

• pure muscarinic activity
• crosses BBB
• has appreciable CNS effects

Question 12

Therapeutic use of PILOCARPINE?

Answer 12

• dry mouth due to head and neck radiotherapy or Sjogren’s syndrome
• open and angle-closure glaucoma

Question 13

What is Sjogren’s syndrome?

Answer 13

AI disorder-immune cells attack and destroy the exocrine gland that produce teas and saliva.

Question 14

Precautions for PILOCARPINE

Answer 14

-administer with care to pts taking beta blocker due to exacerbation of conduction slowing