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44 Cards in this Set
- Front
- Back
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How do ACE inhibitors work?
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By preventing the breakdown of ACh at any synapse at which it works; thus prolonging its effects
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How does the Acetylcholine esterase reaction go basically?
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Serine on the enzyme causes hydrolysis of the ester bond and kicks an Acetate off to free Choline
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Why is the AChesterase reaction special?
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It is highly efficient and one of the fastest reactions known.
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What are the 6 ACE inhibitors?
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ESPN PE
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ESPN PE:
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-Edrophonium
-Sarin -Physostigmine -Neostigmine -Parathion -Echothiophate |
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Which ACE inhibitors are reversible?
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-Edrophonium
-Physostigmine -Neostigmine |
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Which ACE inhibitors are irreversile?
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-Sarin
-Parathion -Echothiophate |
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What type of antagonist is Edrophonium? How does it behave?
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A reversible competitive enzyme inhibitor - rapidly binds to the active site, acts for a short duration.
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What is Edrophonium used for?
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-Diagnosis of Myasthenia gravis
-Distinguishing myasthenic vs cholinergic crisis |
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What can Edrophonium be used to reverse?
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Neuromuscular blocking agents
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What are AChesterase Substrate inhibitors in general?
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Agents that are hydrolyzed by the enzyme but at a slow rate
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What are clinically relevate ACH esterase substrate inhibitors?
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Carbamate derivatives
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What are the 2 important substrate inhibitors of ACE?
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-Physostigmine
-Neostigmine |
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What is the main difference between Physostigmine and Neostigmine?
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-Physostigmine is lipophilic - can have CNS effects
-Neostigmine can't get into CNS |
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What are 2 clinical uses of Physostigmine?
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-Chronic wide angle glaucoma
-Muscarinic and TCA drug poisonings |
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How long does it take for the effects of both Physostigmine and Neostigmine to reverse?
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Hours
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What are the 2 clinical uses of Neostigmine?
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-Post operative atony of gut and bladder
-Treatment of myasthenia gravis |
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What has replaced Neostigmine as a diagnostic tool for Myasthenia gravis?
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Edrophonium
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What does neostigmine do to Ach levels?
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Increases them (prolongs its effects)
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What happens to muscle tone if you give too much Neostigmine?
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Too much ACh - Depolarization blockade; muscle weakness
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What will be the result of not enough Neostigmine though?
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Too much Achesterase - not enough ACh, muscle weakness.
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If a patient with m. gravis has acute muscle weakness, how do you know if it's myasthenic or cholinergic crisis?
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Give edrophonium - if they get better, it was myasthenic; if they get weaker, it's cholinergic crisis.
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What does Edrophonium do if the Neostigmine dose was too high?
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Makes muscles even weaker
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What will Edrophonium do if Neostigmine doses were too low?
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Edrophonium will make muscles stronger
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What will happen if there wasn't enough Neostigmine?
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Muscles will get stronger
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What are the irreversible AchE inhibitors also called??
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Organophosphate ACE inhibitors
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How do the irreversible AchE inhibitors work?
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By phosphorylating the enzyme which inactivates it.
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What are the 3 irreversible AChE inhibitors?
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-Sarin
-Parathion -Echothiophate |
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What is Sarin?
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Nerve gas
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What is Parathion?
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Insecticide
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What is Echothiophate?
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An organophosphate
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What is required to reverse the effects of irreversible AChE inhibitors? How long does it take?
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-Synthesize new enzyme
-Takes several days |
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What is Echothiophate used to treat?
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Glaucoma
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What can be a side effect of the long-term action of topical Echothiophate on the eyes?
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Cataracts
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What will happen if too much inhibition of AChE is done?
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Overactivation of Muscarinic and Nicotinic receptors in both the periphery and CNS!
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What will ACE inhibitor toxicity do in the CNS?
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Depress the medullary respiratory center and cause death due to respiratory failure
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What will ACE inhibitor toxicity do at the NMJ?
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Cause paralysis
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What will ACE inhibitor toxicity do at the lungs?
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-Bronchoconstrict
-Increase secretions |
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What will ACE inhibitor toxicity do to the heart?
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-Bradycardia
-Decrease CO |
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What will ACE inhibitor toxicity do to the GI tract?
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Diarrhea and Urination
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What are the 4 steps to take for treating ACE inhibitor toxicity?
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1. Remove source of poison
2. Maintain patent airway 3. Give Atropine 4. Give Pralidoxine |
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What is Atropine?
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A muscarinic antagonist - blocks the peripheral and central muscarinic activation
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What does Pralidoxime do?
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Reactivates the AChE enzyme peripherally
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When does Pralidoxime have to be given and why?
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Within 2-3 hrs after toxin exposure - because it is not effective against AGED enzyme
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