B4.005 Prework 2 Cholinoreceptor Activating or Blocking Drugs

Question 1

what neurotransmitter do cholinoceptor activating/inhibiting drugs mimic?

Answer 1

ACh

called cholinomimetic agents

Question 2

how are chol agonists classified pharmacologically?

Answer 2

by receptor action
muscarinic- G protein coupled receptrs
nicotinic- ion channels (Na and K)

Question 3

how do direct acting cholinomimetic agents work?

Answer 3

directly bind and activate muscarinic or nicotinic receptors

Question 4

what is the primary action of indirect acting cholinomimetic agents?

Answer 4

inhibit ACh esterase (block hydrolysis of ACh)
increase endogenous ACh concentration in synapse
excess ACh increases response

Question 5

what are 3 properties of modified choline esters?

Answer 5

susceptibility to cholinesterase
muscarinic action
nicotinic action

Question 6

describe the properties of ACh chloride

Answer 6

very susceptible to cholinesterase

high muscarinic and nicotinic action

Question 7

describe the properties of methacholine chloride

Answer 7

less susceptible to cholinesterase
very his muscarinic action
no nicotinic action

Question 8

describe the properties of carbachol chloride

Answer 8

negligible susceptibility to cholinesterase

intermediate muscarinic and nictotinic action (musc

Question 9

describe the properties of bethanechol chloride

Answer 9

negligible susceptibility to cholinesterase
intermediate muscarinic action
no nicotinic action

Question 10

what are the 3 chemical groups of cholinesterase inhibitors (indirect acting cholinomimetics)

Answer 10

1. simple alcohols
2. carbamic acid esters
3. organic derivatives or phosphoric acid (organophosphates)

Question 11

what drugs are in the simple alcohols group and what are the properties of each

Answer 11

edrophonium

-rapidly degraded, short activity

Question 12

what drugs are in the carbamic acid esters group and what are the properties of each

Answer 12

• all are more common and last longer
  1. neostigmine - quaternary ion, acts on periphery
  2. physostigmine- tertiary amine, acts in CNS, prototypic drug in class

Question 13

what drugs are in the organic derivatives of phosphoric acid group and what are the properties of each

Answer 13

• all provide long lasting covalent chelation which can only be overcome by production of new enzymes
  1. soman
  2. sarin
  3. malathion

Question 14

effects of cholinergic transmission (muscarinic agonists) on the cardiovascular system

Answer 14

direct effect = slows HR (rate of contraction)

no innervation of peripheral vasculature, PNS limited to effects on myocardium

Question 15

effects of cholinergic transmission (muscarinic agonists) on other organ systems

Answer 15

contracts smooth muscle and stimulates secretions in:

• respiratory system
• GI tract
• GU tract
• secretory glands (thermoregulatory sweat glands only)

Question 16

major site of action of nicotinic agonists

Answer 16

autonomic ganglia
simultaneous SNS and PNS discharge
predominant tone predicts effects (muscarinic or adrenergic)
-SNS in vasculature
-PNS in most other tissues

Question 17

what are the two subgroups of cholinoceptor blocking drugs?

Answer 17

muscarinic antagonists

nictotinic antagonists

Question 18

subgroups of nicotinic antagonists

Answer 18

ganglion blockers

neuromuscular junction blockers (paralytics) (not in this block)

Question 19

subgroups of antimuscarinic drugs

Answer 19

tertiary compounds used for effects in eye or CNS
- atropine, scopolamine
quaternary amines selectively produce peripheral effects
-ipratropium

Question 20

prototypic antimuscarinic drug

Answer 20

atropine
causes reversible (competitive) blockade
not selective between muscarinic receptor subtypes
causes reverse of parasympathetic activity including increased HR and blockade of secretions of peripheral organs

Question 21

what are examples of nicotinic receptor antagonists?

Answer 21

hexamethonium
trimethaphan
mecamylamine

Question 22

why are nicotinic receptor antagonists often not used?

Answer 22

non selectivity because located on both PNS and SNS autonomic ganglia
this produces a limiting side effect profile bc there is no ability to mount a sympathetic reflex (orthostatic hypotension)

Question 23

first nicotinic antagonist

Answer 23

tetraethylammonium (TEA)
short duration of action
developed for management of hypertension (effective)