Pharmacology of Anticholinesterases and Cholinomimetics

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Questions and Answers

What is the mechanism of action of anticholinesterases?

Inhibit the release of acetylcholine

Stimulate the synthesis of acetylcholine

Inhibit the metabolism of acetylcholine (correct)

Activate the breakdown of acetylcholine

What is the result of anticholinesterases inhibiting acetylcholinesterase?

Reduced duration of action of acetylcholine

Prolonged duration of action of acetylcholine (correct)

Increased synthesis of acetylcholine

Decreased release of acetylcholine

What is a characteristic of reversible anticholinesterases?

Structurally similar to acetylcholine (correct)

Permanently inhibit acetylcholinesterase

Directly stimulate cholinergic receptors

Structurally similar to atropine

Which of the following is a use of reversible anticholinesterases?

Reversal of muscle relaxation Signup and view all the answers

What is the rationale for using atropine in the management of organophosphorus poisoning?

Atropine is a cholinergic receptor antagonist Signup and view all the answers

What is a group of drugs used to treat glaucoma?

All of the above Signup and view all the answers

What is the primary objective of rapid decontamination in initial OP poisoning treatment?

To remove the toxin from the body Signup and view all the answers

Which of the following is a characteristic of muscarinic symptoms in OP poisoning?

Lacrimation Signup and view all the answers

What is the primary mechanism of action of oximes in OP poisoning treatment?

Reactivating acetylcholinesterase Signup and view all the answers

Which of the following drugs is used to control convulsions in OP poisoning?

Diazepam Signup and view all the answers

What is the primary goal of maintaining an intravenous line in OP poisoning treatment?

To administer oximes Signup and view all the answers

What is the golden period for reactivation of acetylcholinesterase in OP poisoning?

Within 2 hours Signup and view all the answers

Which of the following drugs is used to treat glaucoma?

Pilocarpine Signup and view all the answers

What is the primary effect of nicotinic symptoms in OP poisoning?

Muscle paralysis Signup and view all the answers

What is the origin of physostigmine?

Natural alkaloid Signup and view all the answers

What is the solubility characteristic of physostigmine?

Highly lipid soluble Signup and view all the answers

What is a common use of physostigmine?

Management of post-operative paralytic ileus Signup and view all the answers

Which of the following drugs is used to treat Alzheimer's disease?

Rivastigmine Signup and view all the answers

What is the characteristic of edrophonium?

Short acting Signup and view all the answers

What is a common adverse effect of cholinomimetics?

Gastrointestinal upset Signup and view all the answers

What is the effect of aging on organophosphate poisoning?

The covalent bonding between AchE and organophosphates becomes more stable Signup and view all the answers

What is the structure of neostigmine?

Quaternary amine Signup and view all the answers

What is the use of neostigmine in anesthesia?

Reversal of non-depolarizing neuromuscular blockers Signup and view all the answers

What is the effect of cholinomimetics on the eye?

Miosis Signup and view all the answers

Study Notes

Mechanism of Action of Anticholinesterases

Anticholinesterases (AchE) inhibit the breakdown of acetylcholine (ACh) in the synaptic space, leading to an increase in ACh levels.
Reversible AchE inhibitors, such as physostigmine and neostigmine, have a similar structure to ACh and bind to the enzyme, temporarily inhibiting it.
This indirect mechanism allows ACh to accumulate in the synaptic space, leading to a cholinergic effect.

Physostigmine vs Neostigmine

Physostigmine:
Natural alkaloid
Tertiary amine structure
Highly lipid soluble, allowing it to cross the blood-brain barrier
Can cause convulsions at high doses
Neostigmine:
Synthetic derivative
Quaternary amine structure
Not lipid soluble, unable to cross the blood-brain barrier
Less likely to cause convulsions even at high doses

Therapeutic Uses of Reversible Anticholinesterases

Alzheimer's disease: Galantamine, Tacrine, Donepezil, Rivastigmine
Myasthenia gravis: Neostigmine, Pyridostigmine
Post-operative reversal of muscle relaxation: Neostigmine
Atropine poisoning: Physostigmine

Uses of Cholinomimetics

Edrophonium: Short-acting, diagnosis of myasthenia gravis
Physostigmine: Intermediate-acting, treatment of glaucoma and atropine poisoning
Neostigmine: Intermediate-acting, treatment of paralytic ileus, urinary retention, myasthenia gravis, and reversal of non-depolarizing neuromuscular blockers
Donepezil: Lipid soluble, treatment of Alzheimer's disease
Organophosphates: Irreversible inhibitors, used as insecticides and nerve gas

Adverse Effects of Cholinomimetics

SLUDGE syndrome: Salivation, lacrimation, urination, defecation, gastrointestinal upset, and emesis
CNS stimulation
Miosis and spasm of accommodation
Bronchoconstriction and tracheobronchial secretions
AV block

Organophosphate Poisoning and Management

Muscarinic symptoms: Diarrhea, urination, miosis, bronchospasm, bradycardia, lacrimation, emesis, and sweating
Nicotinic symptoms: Muscle fatigue and weakness, twitching, fasciculation, tremors, muscle paralysis
CNS symptoms: Ataxia, confusion, convulsions, depressed respiration, and cardiovascular function
Initial treatment: Rapid decontamination, maintaining respiration, suction of bronchial secretions, catheterization of the urinary bladder, and control of convulsions
Atropine: Antimuscarinic agent, blocks all actions of ACh on muscarinic receptors
Oximes: Cholinesterase reactivators, reactivate AchE inhibited by organophosphates

Reactivation of AchE by Oximes

Golden period: Within 2 hours of exposure, oximes can prevent aging and reactivate AchE

Drugs Used in Glaucoma

Parasympathetic agents: Pilocarpine, physostigmine, dipivefrin, apraclonidine, and brimonidine
Adrenergic agonists: Timolol, levobunolol, carteolol
Beta blockers: Timolol, levobunolol, carteolol
Carbonic anhydrase inhibitors: Acetazolamide, dorzolamide
Prostaglandin analogs: Latanoprost, travoprost
Osmotic agents: Mannitol, glycerin

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Description

This quiz covers the mechanism of action, pharmacological actions, and uses of anticholinesterases, as well as the adverse effects of cholinomimetic drugs. Apply your knowledge to real-world scenarios, such as Alzheimer's and myasthenia gravis.