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Indirect acting parasympathomimetics

Terms in this set (31)

What is meant by "indirect acting"?
-cholinesterase inhibitors
*can be reversible or irreversible
How do indirect parasympathomimetics works?
-they have muscarinic and nicotinic effects via excess Ach
-cholinesterase breaks down Ach; when it is inhibited, there is more Ach present; acts as a cholinergic agonist

-may have direct nicotinic effect on neuromuscular junction (secondary effect)
What type of drugs are indirect-acting parasympathomimetics?
cholinergic agonists

*reversible or irreversible cholinesterase inhibitors
Reversible cholinesterase inhibitors:
-physostigmine
-neostigmine
-edrophonium
-demecarium
Irreversible cholinesterase inhibitors:
*organophosphates:
-opthalmic
-anthelmintics
-ectoparasiticides and insecticides
What kind of compound is physostigmine?
-a tertiary amine (good penetrator of membs)
What is physostigmine commonly used for?
-as an opthalmic agent to treat open-angle glaucoma
Should physostigmine be used for closed-angle glaucoma?
NO, it may aggravate it
For which patients should you use physostigmine with extreme caution?
those with seizures bc it can **cross the BBB (good penetrator)
What does physostigmine counteract?
-many central and peripheral effects of anticholinergic drugs (parasympatholytics/cholinergic antagonists) such as atropine
-and is used for Datura spp poisoning
How is physostigmine administered?
-parenterally (IV or IM)
*for overdose/poisoning of atropine
-topically on the eye
Duration of action for physostigmine:
IV: 1-2 hours
after opthalmic use: 12-36 hours
What kind of compound is neostigmine?
-a quaternary amine parasympathomimetic (indirect acting cholinergic agonist)
What is neostigmine used for?
-to antagonize the effects of non-depolarizing muscle relaxants (tubocurarine)
-causes sk mm contraction

*antidote for curare-like drugs
What clinical disease is neostigmine associated with?
-treatment and diagnosis of myasthenia gravis
What else is neostigmine used for?
-as a prokinetic to stimulate GIT motility
-to treat postoperative non obstructive urinary retention (like bethanechol) to cause urination
How is neostigmine administered?
orally and parenterally
Neostigmine has a longer duration of action than which drug?
edrophonium
What kind of compound is edrophonium?
-a quaternary amine (like neostigmine)
What disease is associated with edrophonium?
*myasthenia gravis

-it is the drug of choice for diagnosing MG, but NOT for treating it
How is edrophonium administered?
parenterally
Edrophonium onset and duration of action:
-rapid onset
-short duration of action

*neostigmine has a longer duration of action than edrophonium
What is an advantage of edrophonium's short duration of action?
-less adverse side effects
What type of compound is pyridostigmine?
-a quaternary amine
What disease is pyridostigmine used to treat?
-myasthenia gravis

*pryidostigmine is preferred for treatment of MG
How is pyridostigmine administered?
orally
Duration of action of pryidostigmine:
longer than neostigmine

pyridostigmine>neostigmine>edrophonium
Which drug is used to treat toxicity of cholinesterase inhibitors (indirect-acting parasympathomimetics)?
atropine
What kind of compound is demecarium?
-a carbamate reversible cholinesterase inhibitor (indirect acting parasympathomimetic)
What is demecarium used for?
-topical opthalmic miotic (pupil constriction) agent

-used for open-angle glaucoma
Duration of action of demecarium:
as long as opthalmic organophosphates: 12-48 hours
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