Ch 7 - Cholinergic Antagonist

Question 1

Name the two subdivistions of neuromusclular agents:

Answer 1

1. Nondepolarizing blocking agents

2. Depolarizing blocking agents

Question 2

Name four nondepolarizing blocking agents:

Answer 2

1. Tubocurarine
2. Pancuronium (longer duration action than Tubocrurarine)
3. Atracurium (suitable for short surgical procedures)
4. Vecorium

Question 3

What is the machanism of action of nondepolarizing blocking agents?

Answer 3

These drugs competitively block cholinergic transmission at the nicotinic neuromuscular receptor (Nm) by preventing binding of acetylcholine to its receptors

Question 4

What is the therapeutic use of the nondepolarizing blocking agents?

Answer 4

They are used as adjuvant drugs for anesthesia- they promote muscle relaxation

Question 5

Are all muscles equally effected during the use of nondepolarizing blocking agents?

Answer 5

No. The muscles of the eye and face are affected first, wheras the respiratory muscles are affected last

Question 6

What is the route of asministration of nondepolarizing blocking agents?

Answer 6

IV

Question 7

Nondepolarizing blocking agents AE:

Answer 7

bronchoconstriction and hypotension, caused by histamine release

Question 8

What can be used to counteract the effects of the nondepolarising blocking agents?

Answer 8

Because neuromusclular junction blockers are competitive inhibitors, their action can be reversed with endrophonium or neostigmine

Question 9

Name depolarizing blocking agent:

Answer 9

Succinylcholine

Question 10

What is the duration of action of Succinylcholine?

Answer 10

3-6 min if given as a single dose

Question 11

What substances metabolises Succinylcholine?

Answer 11

Plasma choliesterase

Question 12

How is succinylcholine used clinically?

Answer 12

• As an adjuvant to general anesthesia

- To facilitate rapid intubation

Question 13

What are the adverse effects of Succinylcholine?

Answer 13

• Bronchoconstriction caused by histamine release
• Hypotension
• Arrhythmias
• Apnea due to respiratory paralysis
• Malignant hyperthermia when used with Halothene

Question 14

How is malignant hyperthermia treated?

Answer 14

By rapid cooling and the administration of Dantrolene.
Dantrolene blocks the release of Ca2+ from the sarcoplasmic reticulum, which reduces skeletal muscle contraction and subsequent heat production

Question 15

Do neuromuscular blocking agents block autonomic ganglia as well?

Answer 15

In general, no. The skeletal muscle end plate and autonomic ganglia use different subtypes of nicotine receptors.

Tubocurarine can, however, produce a small amount of ganglionic blockade.

Question 16

Name four ganglionic blockers:

Answer 16

1. Nicotine
2. Hexamethonium
3. Mecamylamine
4. Trimethaphan

Question 17

What do the ganglionic blockers do?

Answer 17

Ganglionic inhibitors compete with acetylcholine to bind with nicotinic receptors of both parasympathetic and sympathetic ganglia

Question 18

What is the mechanism of action of ganglionic blockers?

Answer 18

Ganglionic blockers can be divided into two groups:

1. Drugs such as nicotine, which initially stimulate the ganglia and then block them because of a persistant depolarizaton
2. Drugs such as Hexamethonium, Mecamyalamine, and Trimethaphan, which block ganglia without any prior stimulation.

Question 19

READ the physiological effect of succinulcholine

Answer 19

P.50

Question 20

What is the therapeutic use of Succinylcholine?

Answer 20

Because they lack selectivity, the ganglionic blockers have been largely phased out of clinical use.
In the past, these drugs were used in hypertensive emergencies.

Question 21

What are the adverse effects of Succinylcholine?

Answer 21

The toxicities of ganglionic blockers are identical to their physiological effects.