Cholinesterase Inhibitors/Myasthenia Gravis Flashcards Preview

Pharmacology > Cholinesterase Inhibitors/Myasthenia Gravis > Flashcards

Flashcards in Cholinesterase Inhibitors/Myasthenia Gravis Deck (17):
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Cholinesterase Inibitors

Drugs that prevent the degradation of ACh by acetylcholinesterase; viewed as indirect acting cholinergic agonists
-lack sensitivity, limited therapeutic applications

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Reversible cholinesterase inhibitors

Neostigmine, other reversible cholinesterase inhibitors

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Irreversible cholinesterase inhibitors

Basic pharmacology, toxicology

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Neostigmine (Prostigmin)

Cannot readily cross membranes, absorbed poorly with oral administration, minimal effects on brain and fetus, poor substrate for cholinesterase (ChE)

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Neostigmine: Pharmacologic effects

Therapeutic administration: muscarinic receptors

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Neostigmine: muscarinic responses

Identical to muscarinic agonist response

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Neostigmine: neuromuscular effects

Therapeutic dose: increases force of contraction in skeletal muscle; toxic levels: decrease force of contraction

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Neostigmine: central nervous system

Therapeutic levels: mild stimulation, toxic levels: CNS depression

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Neostigmine: therapeutic uses

Myasthenia gravis; reversal of nondepolarizing neuromuscular blockade

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Neostigmine: adverse effects

Excessive muscarinic stimulation, neuromuscular blockade, treatment with antagonist

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Neostigmine: precautions and contraindications

Obstruction of GI or urinary tract, peptic ulcer disease, asthma, coronary insufficiency, hyperthyroidism

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Neostigmine: drug interactions

Muscarinic antagonists, nondepolarizing neuromuscular blockers, depolarizing neuromuscular blockers

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Other "reversible" cholinesterase inhibitors

Physostigmine, ambenonium, edrophonium, pyridostigmine, drugs for Alzheimer's disease

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"Irreversible" cholinesterase inhibitors

Highly toxic, primarily used as insecticides, only clinical application is glaucoma, all contain an atom of phosphorus, almost all are highly lipid soluble, readily absorbed from several routes, potential use in chemical warfare

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Myasthenia Gravis

Characterized by fluctuating muscle weakness and predisposition to rapid fatigue; common symptoms: ptosis, dysphagia, weakness of skeletal muscles
-Autoimmune process in which antibodies attack nicotinic(M) receptors on skeletal muscles

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Myasthenia gravis treatment

Cholinesterase inhibitors; beneficial effects: increased muscle strength/side effects: excessive muscarinic response
Dosage/adjustment: start small and modify; signs of undermedication: ptosis, dysphagia vs. overmedication: excessive salivation, muscarinic respones

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Cholinergic crisis

Characterized by extreme muscle weakness or frank paralysis and signs of excessive muscarinic stimulation; treatment with respiratory support and atropine