Nicotinic Receptor Antagonists

Question 1

Nicotinic Receptor Antagonist Clinical Uses

Answer 1

Muscle relaxation during surgery
• particularly important in intra-abdominal surgeries

Tracheal intubation
• relax pharyngeal and laryngeal muscles
• this activity facilitates laryngoscopy and placement of the tracheal tube during
general anesthesia

Control of ventilation (patients with ventilatory failure)
•often used in the ICU setting for critically ill patient
•reduce chest wall resistance

Treatment of convulsions
•sometimes used to alleviate peripheral component of convulsions associated with
status epilepticus or local anesthetic toxicity
• no effect on CNS component because these drugs don’t penetrate the blood-brain
barrier

Question 2

How to restore patients after use of anti nicotinic drugs

Answer 2

-give acetylcholinesterase inhibitor after a procedure that builds up acetylcholine to restore function

Question 3

Nicotinic Receptor - Depolarizing Competitive

[Toilet Example]

Answer 3

Depolarizing competitive
● these drugs bind the nicotinic receptor and keep it
in an open state, resulting in a continued influx of
Na+ ions and thus persistent membrane
depolarization.
● the depolarized membrane takes a long time to
repolarize and during this time is unresponsive to
new impulses.
● A two-phase process

Question 4

Succinylcholine [Neuromuscular Blocker]

Answer 4

• ONLY depolarizing drug
• neuromuscular blockers are limited in their clinical use and application

-DURATION OF ACTION: These drugs have an EXTREMELY
SHORT duration of action (succinylcholine ~5-10 min)

• its action is terminated via hydrolysis by plasma pseudocholinesterase
  (drug must diffuse away from end plate) - LOOKING TO BREAK DOWN non-stable ESTER
• can cause cardiac arrythmias because it stimulates all autonomic
  acetylcholine receptors (sympathetic and para- sympathetic ganglia, M2
  receptors in SA node)

Question 5

Nicotinic Receptor - Nondepolarizing Competitive

Answer 5

● these drugs bind the nicotinic receptor and
keep it in a closed state, with no influx of Na+
ions.
● these drugs act as classic competitive inhibitors
by blocking the access of acetylcholine (they can
be displaced from the receptor by acetyl-choline
as well)

Question 6

d-turbocurarine

[Non-Depolarizing Neuromuscular Blockers]

Answer 6

-Used in as an adjunct to anesthesia to provide musc
relaxation during surgery
- constituent of ‘curare’, an arrow poison used by Sou
American Indians
- d-tubocurarine is NOT orally active, and is given
parenterally, usually iv.
- the drug has 30-60 min duration of action.
-overdose is managed by maintaining respiration, or i
reversed by acetylcholinesterase inhibitors (e.g.
neostigmine).

Question 7

pancuronium

[Non-Depolarizing Neuromuscular Blockers]

Answer 7

• about 6 times more potent than dtubocurarine

- synthetic

Question 8

atracurium

rocuronium

mivacurium

[Non-Depolarizing Neuromuscular Blockers]

Answer 8

• Used in surgical procedures and intubation
• Rapid acting neuromucular blockers (onset 1-2 mins after iv administration)
• High degree of flexibility in these molecules

Question 9

Duration of Action of Neuromuscular Blockers

Answer 9

• vecuronium (30 - 60 min)
• pancuronium (45 - 90 min)
• mivacuronium (15 - 20 min)
• rocuronium (30 - 45 min)

-succinylcholine (4 - 5 min)