Ch 7 - Cholinergic Antagonist Flashcards
Name the two subdivistions of neuromusclular agents:
- Nondepolarizing blocking agents
2. Depolarizing blocking agents
Name four nondepolarizing blocking agents:
- Tubocurarine
- Pancuronium (longer duration action than Tubocrurarine)
- Atracurium (suitable for short surgical procedures)
- Vecorium
What is the machanism of action of nondepolarizing blocking agents?
These drugs competitively block cholinergic transmission at the nicotinic neuromuscular receptor (Nm) by preventing binding of acetylcholine to its receptors
What is the therapeutic use of the nondepolarizing blocking agents?
They are used as adjuvant drugs for anesthesia- they promote muscle relaxation
Are all muscles equally effected during the use of nondepolarizing blocking agents?
No. The muscles of the eye and face are affected first, wheras the respiratory muscles are affected last
What is the route of asministration of nondepolarizing blocking agents?
IV
Nondepolarizing blocking agents AE:
bronchoconstriction and hypotension, caused by histamine release
What can be used to counteract the effects of the nondepolarising blocking agents?
Because neuromusclular junction blockers are competitive inhibitors, their action can be reversed with endrophonium or neostigmine
Name depolarizing blocking agent:
Succinylcholine
What is the duration of action of Succinylcholine?
3-6 min if given as a single dose
What substances metabolises Succinylcholine?
Plasma choliesterase
How is succinylcholine used clinically?
- As an adjuvant to general anesthesia
- To facilitate rapid intubation
What are the adverse effects of Succinylcholine?
- Bronchoconstriction caused by histamine release
- Hypotension
- Arrhythmias
- Apnea due to respiratory paralysis
- Malignant hyperthermia when used with Halothene
How is malignant hyperthermia treated?
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
Do neuromuscular blocking agents block autonomic ganglia as well?
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.
Name four ganglionic blockers:
- Nicotine
- Hexamethonium
- Mecamylamine
- Trimethaphan
What do the ganglionic blockers do?
Ganglionic inhibitors compete with acetylcholine to bind with nicotinic receptors of both parasympathetic and sympathetic ganglia
What is the mechanism of action of ganglionic blockers?
Ganglionic blockers can be divided into two groups:
- Drugs such as nicotine, which initially stimulate the ganglia and then block them because of a persistant depolarizaton
- Drugs such as Hexamethonium, Mecamyalamine, and Trimethaphan, which block ganglia without any prior stimulation.
READ the physiological effect of succinulcholine
P.50
What is the therapeutic use of Succinylcholine?
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.
What are the adverse effects of Succinylcholine?
The toxicities of ganglionic blockers are identical to their physiological effects.
