Exam 2 - Drugs Targeting the Neuromuscular Junction Flashcards
What is a synapse? (structure and function)
- the structure formed between a motor neuron and muscular fiber
- transmit nerve impulses between neurons or a neuron and a target cell
How does myasthenia gravis disrupt the signaling at NMJ?
the production of antibodies attach acetylcholine receptors on muscle cell surfaces
* blocks the binding of acetylcholine
How can myasthenia gravis be treated?
AChE inhibitors (neostigmine) effectivelt increase ACh concentration at the NMJ, causing more Nm channels to open = more muscle contraction
What do neuromuscular blocking agents do?
inhibit Nm = suppressing muscle contraction
What are the therapeutic uses of neuromuscular blocking agents?
- muscle relaxation
- tracheal intubation
- reduce convulsions
What are 2 important things to consider when using neuromuscular blocking agents?
- respiration
- cardiovascular function
What is important to remember about molecules with quarternary N groups?
poor lipid solubility and inability to cross BBB
Describe nondepolarizing neuromuscular blocking agents.
competitive antagonist, prevents depolarization = reducing muscle contractions
What is the mechanism of action for nondepolarizing neuromuscular blocking agents?
blocking agents bind to Nm receptor but do not activate/depolarize the cell = prevention of muscle contraction
What are examples of nondepolarizing neuromuscular blocking agents?
- D-tubocurarine
- pancuronium
- cistracurium
- veceronium
Can an AChE (neostigmine) reverse the effects of nondepolarizing neuromuscular blocking drugs?
- yes
- neostigmine elevates ACh allowing it to compete nondepolarizing agent off
What are contraindications of nondepolarizing neuromuscular blocking drugs?
- use w/ antibiotics (increase NMJ block)
- myasthenia gravis
Describe depolarizing neuromuscular blocking agents.
initially noncompetitive agonist (depolarization) then causes persistent inhibition = reducing muscle contraction
What is the mechanism of action for depolarizing neuromuscular blocking drugs?
Phase 1
* depolarize membrane so it cannot respond to later impulses
Phase 2
* membrane repolarizes but it resistant to depolarization (desensitization)
What is an example of depolarizing neuromuscular blocking drugs?
succinylcholine
Can an AChE inhibitor (neostigmine) reverse the effects of depolarizing neuromuscular blocking drugs?
no
What are the contraindications of depolarizing neuromuscular blocking agents?
organophosphate poisoning
