Cholinergic Antagonists

Question 1

Cholinergic antagonists

• antimuscarinic
• ganglionic blockers
• neuromuscular blockers
  a) nondepolarizing
  b) depolarizing

Answer 1

Antimuscarinic

• atropine
• ipratropium
• scopolamine
• thiotropium

Ganglionic blockers -> rarely used therapeutically -> experimental pharmacology

• nicotine
• trimethaphan
• mecamylamine

Neuromuscular blockers

a) Non depolarizing
- tubocurarine
- pancuronium
- vecuronium
- mivacurium
- metacurine
- doxacurium
- atracurium

b) Depolarizing
- succinylcholine
- isuxamethonium

Question 2

Atropine

• blind as a bat
• dry as a bone
• hot as a hare
• red as a beat

Answer 2

Alkaloid
Actions last = 4hs
Pharmacokinetics:
- readily absorbed
- partially metabolized in liver

M blocker (competitive)

TU:

• mydriasis and cyclopegia
• antispasmodic agent
• used in enuresis
• cutaneous vasodilation
• blockage of salivary, sweat and lacrimal glands
• antidote for cholinergic agonists

AE:

• dry mouth
• blurred vision, sandy eyes
• tachycardia
• constipation
• restlessness, confusion
• hallucination, delirium

Antidote: physostigmine

Question 3

Scopolamine

Answer 3

Belladonna alkaloid

M blocker

TU:

• 1 of the most effective antimotion sickness, prevention of Mersin
• blocks short-term memory (anesthetic procedures)

Question 4

Ipatropium

Answer 4

1ry derivative of atropine

TU: inhaled - asthma, COPD (in pts unable to take adrenergic agonists)

Question 5

Nicotine

Answer 5

TU: Depolarizes ganglia, 1st stimulation and then paralysis of the ganglia

Question 6

Mecamylamine

Answer 6

TU:

• competitive nicotine can ganglionic block
• approximately 10h of action after single dose administration
• oral absorption is good (in contrast to trimethaphan)

Question 7

Trimethaphan

Answer 7

TU:

• short-acting, competitive N ganglionic blocker
• must be given i.v.
• used for emergency lowering of BP

Question 8

Tubocurarine (30-60min)
Pancuronium (1-2h)
Mivacurium
Metacurine
Doxacurium
Vecuronium (30-40min)

Answer 8

PK:

• i.v. Injected
• don’t enter cells and BBB
• many aren’t metabolized
• only redistributed and excreted in urine

TU:

• adjuvant drugs in anesthesia
• during surgery to relax skeletal mm

AE:

• hypotension due to ganglionic block
• bronchoconstriction

Question 9

Succinylcholine

Answer 9

10min
Initially produces short-lasting mm fasciculations followed w/in min by paralysis.
Doesn’t produce ganglionic block except in high doses.
Weak histamine-releasing action -> extremely short duration of action

PK: i.v. (Usually continuous infusion)

TU:

• endotracheal intubation
• electroconvulsive shock treatment

AE:

• hyperthermia
• apnea
• hyperkalemia (K+ release)
• bradycardia
• increase iop
• prolonged paralysis
• malignant HT (if administered w/ halothane)