MPP: BLOCK 2: SKELETAL MUSCLE PHARMACOLOGY

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Questions and Answers

What is the underlying genetic cause of Duchenne muscular dystrophy (DMD)?

An autosomal dominant mutation in the dystrophin gene

A recessive X-linked mutation in the dystrophin gene (correct)

A dominant Y-linked mutation affecting muscle function

An XY linked mutation in the dystrophin gene

How does antisense therapy function in the treatment of DMD?

It enhances the function of existing dystrophin

It replaces dystrophin with a synthetic version

It targets mRNA to increase dystrophin production (correct)

It inhibits the production of dystrophin

What is the primary mechanism of action of cholinergic antagonists?

To increase the release of acetylcholine from motor neurons

To block the action of acetylcholine on its receptors (correct)

To enhance synaptic transmission at the neuromuscular junction

To prevent the breakdown of acetylcholine in the synaptic cleft

Which of the following describes Myasthenia Gravis (MG)?

An autoimmune disorder that affects muscle transmission Signup and view all the answers

What role do neuromuscular blocking agents (NMBAs) play in muscle physiology?

They block the action of acetylcholine leading to muscle paralysis Signup and view all the answers

What happens to an action potential when neuromuscular blocking agents are used?

It may decrease or fail to generate leading to muscle paralysis Signup and view all the answers

Which of these statements is true regarding the mechanism of action of acetylcholinesterase (AChE) inhibitors?

They prevent the breakdown of acetylcholine Signup and view all the answers

In relation to muscle physiology, what is the consequence of dystrophin deficiency in DMD?

Loss of attachment between the cytoskeleton and sarcolemma Signup and view all the answers

What is the primary goal of Eteplirsen in the treatment of Duchenne muscular dystrophy?

Slow or prevent disease progression Signup and view all the answers

What do indirect-acting cholinergic agonists primarily do?

Prevent the degradation of acetylcholine Signup and view all the answers

Which of the following is a reversible acetylcholinesterase inhibitor that is short-acting?

Edrophonium Signup and view all the answers

In myasthenia gravis, what is primarily affected?

Nerve impulse transmission at the neuromuscular junction Signup and view all the answers

What is the mechanism of action of physostigmine?

Inhibits acetylcholinesterase Signup and view all the answers

Which adverse effect is commonly associated with the use of acetylcholinesterase inhibitors?

Salivation and flushing Signup and view all the answers

What is the main clinical use of Edrophonium?

Diagnosis of myasthenia gravis Signup and view all the answers

Neostigmine is primarily used to manage symptoms of which condition?

Myasthenia gravis Signup and view all the answers

Which type of neuromuscular blocking agent acts as a non-depolarizing antagonist?

Pancuronium Signup and view all the answers

Which condition is contraindicated for the use of physostigmine?

Intestinal obstruction Signup and view all the answers

Which class of drugs is used to block the effects of acetylcholine?

Anticholinergic agents Signup and view all the answers

What is the action of succinylcholine at the neuromuscular junction?

Depolarizes the muscle fiber Signup and view all the answers

What distinguishes non-depolarizing neuromuscular blocking agents from depolarizing agents?

Onset and duration of action Signup and view all the answers

Which neuromuscular blocking agent is known for having one of the shortest durations of action?

Rocuronium Signup and view all the answers

Study Notes

Cholinergic Agonists: Acetylcholinesterase Inhibitors

Acetylcholinesterase (AChE) breaks down acetylcholine (ACh)
Anticholinesterase drugs inhibit AChE, leading to ACh accumulation in the synaptic cleft
There are three main types of anticholinesterase drugs: Edrophonium, Physostigmine, and Neostigmine
Edrophonium is a short-acting AChE inhibitor, used for diagnosis of Myasthenia Gravis (MG)
- It binds reversibly to AChE, preventing ACh degradation
- IV injection leads to rapid increase in muscle strength, useful for MG diagnosis
Physostigmine is an intermediate-acting AChE inhibitor
- It forms a stable intermediate with AChE, inhibiting its activity
- Results in increased cholinergic activity throughout the body
- Used to manage MG symptoms and for increasing intestinal and bladder motility
- Adverse effects include generalized cholinergic stimulation: salivation, flushing, decreased blood pressure, nausea, abdominal pain, diarrhea, and bronchospasm
- Contraindicated in intestinal/urinary bladder obstruction
Neostigmine also reversibly inhibits AChE, with intermediate duration of action
- It is less absorbed orally and does not enter the CNS
- More effective in stimulating skeletal muscle compared to physostigmine
- Used to stimulate the bladder and GI tract, and to manage MG symptoms
- Similar adverse effects to physostigmine, and contraindicated in intestinal/urinary bladder obstruction

Therapy for Duchenne Muscular Dystrophy (DMD)

DMD is caused by mutations in the dystrophin gene, leading to loss of dystrophin function
Dystrophin is a protein that links the cytoskeleton to the sarcolemma, its absence leads to muscle fiber necrosis and wasting
Eteplirsen is an "anti-sense therapy" for DMD
- It uses antisense oligonucleotides to target dystrophin pre-mRNA
- It binds to the pre-mRNA and alters splicing, leading to increased production of a partially functional dystrophin
- This increases the quantity of abnormal but functional dystrophin, potentially slowing the progression of DMD

Myasthenia Gravis (MG)

An autoimmune disease affecting neuromuscular transmission
Antibodies against nicotinic acetylcholine receptors interfere with normal signaling at the neuromuscular junction (NMJ)
Results in muscle weakness, which can vary in severity
Treatment includes anticholinesterase inhibitors

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Description

This quiz explores cholinergic agonists, focusing on acetylcholinesterase inhibitors and their mechanisms. Learn about the key drugs such as Edrophonium, Physostigmine, and Neostigmine, as well as their therapeutic uses and side effects in managing conditions like Myasthenia Gravis. Test your understanding of the cholinergic system and how these drugs impact muscle strength and cholinergic activity.