30 Questions
What is the origin of Physostigmine?
Natural alkaloid
What is the difference in solubility between Physostigmine and Neostigmine?
Physostigmine is highly lipid soluble, Neostigmine is not
What is a common use of Physostigmine?
All of the above
Which of the following is used in the diagnosis of myasthenia gravis?
Edrophonium
What is the effect of muscarinic poisoning on the eyes?
Miosis
What is the characteristic of Donepezil?
Lipid soluble, long acting
What is the main goal of rapid decontamination in op poisoning?
To prevent further absorption of the toxin
What is a common adverse effect of cholinomimetics?
SLUDGE syndrome
What happens to the covalent bonding between AchE and organophosphates during aging?
It becomes more stable and irreversible
What is the golden period for reactivation of AchE in op poisoning?
Within 2 hours of exposure
What is the function of oximes in op poisoning management?
To reactivate cholinesterase
What is the use of Neostigmine in anesthesia?
Reversal of muscle relaxation
What is a characteristic of Organophosphates?
Irreversible inhibitor of AchE
What type of drugs are pilocarpine and physostigmine?
Parasympathetic agents
What is the effect of nicotinic poisoning on the muscles?
All of the above
What is a CNS effect of cholinomimetics?
CNS stimulation
What is the role of atropine in op poisoning management?
To block the actions of acetylcholine
What is the mechanism of action of anticholinesterases?
Inhibit AchE
What is the primary cause of death in severe acute op poisoning?
Cardiopulmonary failure
What is the function of suctioning bronchial secretions in op poisoning management?
To reduce bronchospasm
What is the result of inhibiting AchE?
Prolonged duration of action of ACh
What is the role of diazepam in op poisoning management?
To control convulsions
What is the characteristic of reversible AchE?
Structurally similar to ACh
What is the effect of anticholinesterases on the synaptic space?
Increased accumulation of ACh
What is the use of physostigmine and neostigmine?
All of the above
What is the adverse effect of cholinomimetic drugs?
Increased salivation
What is the rationale for using atropine in the management of organophosphorus poisoning?
Atropine is an antagonist of ACh
What is the manifestation of organophosphorus poisoning?
Cholinergic crisis
What is the management of organophosphorus poisoning?
All of the above
What are the groups of drugs used in glaucoma?
All of the above
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
This quiz covers the mechanism of action, uses, and adverse effects of anticholinesterases, including physostigmine and neostigmine, in conditions like Alzheimer's and myasthenia gravis.
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