341 - NMJ Drugs

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Author:
estee08
ID:
107696
Filename:
341 - NMJ Drugs
Updated:
2011-10-10 20:40:28
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pharmacy
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Description:
PHAR 341 Neuromuscular Junction Drugs
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  1. Vesamicol
    • Presynaptic Mechansim
    • Blocks ACh uptake into storage vesicles - results in a depletion of ACh
    • Not selective
  2. Hemicholinium
    • Presynaptic Mechansim
    • Blocks choline uptake back into the presynaptic terminal - results in less ACh being produced
    • Not selective
    • Can't be overcome by increasing ACh (because it's an open channel block of all nicotinic receptors)
  3. Black Spider Widow Toxin
    • Presynaptic Mechanism
    • Empties synaptic vesicles and prevents them from refilling - results in a massive release of ACh
    • Trasmission across the NMJ is blocked and a paralysis of respiratory muscles results
  4. 4-aminopyridine (4-AP)
    • Presynaptic Mechanism
    • It blocks nerve fibre K+ channels and causes a prolonged action potential - results in more ACh being released
    • Multiple Sclerosis: Small trials have inidcated that high doses of 4-AP has shown improvement
    • Myasthenia Gravis: rarely used for this now
    • Spinal Cord Injury: some promising results from small clinical trials
  5. Acetylcholinesterase Inhibitors
    • Presynaptic Mechansim
    • Examples: pyridostigmine, neostigmine
    • They inhibit the breakdown of ACh in the synaptic cleft - results in more ACh being present
    • Drug of choice for myasthenia gravis
  6. Botulinum Toxin A (Botox) & B (Myobloc)
    • Presynaptic Mechanism
    • It blocks the vesicular release of ACh by cleaving docking proteins (Toxin A/Botox cleaves SNAP 25, Toxin B/Myobloc cleaves VAMP/Synaptobrevin) - results in less ACh in the synapse
    • Results in the weakening to flaccid paralysis of skeletal muscles
    • Reversal takes 3-4 months
    • Myobloc has a shorter action than Botox
    • Cosmetic: treatment of frown lines, forhead lines, orbital lines
    • Opthalmic: treatment of strabismus (lazy eye) and blepharospasm (spasmodic winking)
    • Face and Neck Muscle Spasms
    • Hyperhidrosis: treatment of excessive sweating
    • Pain: may decrease migraine headaches and lower back pain
    • Contraindications: not be used in patients with NMJ disorders (ex. myasthenia gravis, multiple sclerosis)
    • Side Effects: local weakness of muscles at site of injection, ptosis (drooping eyelid), flu-like symptoms, long term use can alter muscle fiber size
  7. Tubocurarine
    • Non-depolarizing Postsynaptic Mechanism
    • It binds to the nicotinic receptor and blocks ACh binding (blocking can be overcome by high number of ACh)
    • IV Route
    • Surgical Muscle Relaxation and Mechanical Ventilation (prevents respiratory effort from patient)
  8. Pancuronium
    • Non-depolarizing Postsynaptic Mechanism
    • It binds to the nicotinic receptor and blocks ACh binding (blocking can be overcome by high number of ACh)
    • IV Route
    • Surgical Muscle Relaxation and Mechanical Ventilation (prevents respiratory effort from patient)
  9. Atacurium
    • Non-depolarizing Postsynaptic Mechanism
    • It binds to the nicotinic receptor and blocks ACh binding (blocking can be overcome by high number of ACh)
    • IV Route
    • Surgical Muscle Relaxation and Mechanical Ventilation (prevents respiratory effort from patient)
  10. α Bungarotoxin
    • Cobra venom
    • Non-depolarizing Postsynaptic Mechanism
    • It binds to the nicotinic receptor and blocks ACh binding (blocking can be overcome by high number of ACh)
    • Bite route
  11. Succinylcholine
    • Depolarizing PostSynaptic Mechansim
    • It binds and activates the nicotinic receptor (acts like ACh) - results in muscle contraction
    • The nicotinic receptor becomes desensitized over time
    • IV route, rapidly broken down
    • Side effects: Stimulates all nicotinic and cholinergic receptors (not selective), arrhythmias, bradycardia, emesis (vomiting), muscular pain, increased intraocular pressure
    • Contraindications: People with fractures, glaucoma patients, and paraplegia patients (it could cause excessive loss of K+)
  12. Dantrolene
    • It reduces the release of Ca2+ which results in less muscle contraction (it does not block neuromuscular tramission)
    • Taken orally
    • Malignant hyperthermia: malignant hyperthermia is caused by a large release of Ca2+ which leads to an increase of body temperature. Drug of choice for this.
    • Spasticity

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