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47 Cards in this Set
- Front
- Back
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What are the 2 major therapeutic groups of Skeletal muscle relaxants?
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Neuromuscular Blockers -used during surgical procedures and in ICU to cause paralysis
Spasmolytics - used to reduce spasticity in a variety of neurological conditions |
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What are 2 mechanisms to accomplish Neuromuscular blockade?
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Antagonists -Non Depolarizing Blockers
Agonist - Depolarizing blockers |
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Neuromuscular blockers bear a stuctural resemblance to ..?
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Acetylcholine
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Non-depolarizing blocking drugs are cassified according to chemical structure into two groups namely....?
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Benzyl-iso-quinolones
Ammonio steroids |
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Name the four Amminio steroids.
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Pancuronium
Pipecuronium Rocuronium Vecuronium |
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List the Benzyl-iso-quinolones?
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Tubocurarine -older
Atacurim Cisatracurim Doxacurim Mivacurim |
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Non-depolarizing blockers are what type of Antagonist?
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Competitive Antagonists
They bind Nicotinic receptor. TUBOCURARINE is the prototype |
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How can the action of non-depolarizing blockers be overcome?
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By increasing the concentration of Ach at the synapse
This can be acheived with Anticholinesterase - Neostigmine, Edrophonium |
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Succinylcholine is what type of neuromuscular agent?
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Depolarizing agent - The Only one available
It is an agonist |
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How does Succinylcholine cause Flaccid Paralysis?
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They activate the Nicotinic receptors and depolarizes the junction and remain bound to the receptor
It is not metabolized effectively by acetylchlinesterase Therefore the membrane remains depolarized and unresponsive to additional impulses |
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What causes neuromuscular blockers to be polar and poorly soluble in lipids?
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They contain Quaternary ammonium groups
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How are NM blockers administered
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Either IM or IV
If given orally they are inactive They penetrate membranes slowly |
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Can NM blockers cross the BBB?
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NO
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Which Non- depolarizing NM blocker is short acting
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Mivacurium
This is due to its Hydrolysis by Plasma cholinesterases |
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What does Atracurium, Cisatracurium, Rocuronium and Vecuronium have in common?
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They are Intermediate acting Non- depolarizing NM blocker
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Which 2 Non- depolarizing NM blockers undergo HOFFMAN degradation (spontaneous degradation)?
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*Atracurium (also eliminated by plasma esterases)
*Cis-atracurium - the stereoisomer of atracurium All others undergo elimination via Renal and Hepatic means (Except for Mivacurium also) Thes 3 that are independent of the P450 mechanism need not be dose adjusted for patients with liver or renal disease |
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What is the duration of action of the Depolarizing blocker-Succinylcholine?
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Extremely brief (5-10 mins)
This is due to Hydrolysis by: 1. Pseudocholinesterase in PLasma 2. Butyrylcholinesterase in Liver |
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NM blockade by succinylcholine is prolonged in what type of patients?
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Patients with an ABNORMAL Variant of Plasma Cholinesterase
Treated with Continued Mechanical Ventilation until muscle function returns to normal |
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What is the first effect of non-dep. NM blockers on muscle?
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First they cause Motor Weakness
then--->Flaccidity--->Inexcitable to stimulation |
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What is the first effect of dep. NM blocker on muscle?
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Succinylcholine causes Transient Fasciculations -Patient may wake in pain
To avoid this a small dose of Non-dep agent is given 1st |
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The onset of NM blockade by Succinylcholine is ...?
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Very rapid - within 1 minute
Duration of block is 5-10 mins (Hydrolysis by plasma and liver cholinesterases) |
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Which group of Non-dep NM blockers release HISTAMINE?
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BENZYL-ISO-QUINOLONES
Mivacurium Doxacurium Atracurium Cis-atracurium Tubocurarine This caused Vasodilation and decrease in BP during operation |
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Which BENZYL-ISO-QUINOLONE does not release Histamine?
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Cis-atracurium (even at high doses)
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The BENZYL-ISO-QUINOLONES -Tubocurarine and Metocurarine release HIstamine at what dosage?
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Normal Clinical dose (they are older drugs)
Newer ones like Atracurium and Mivacurium release Histamine at HIGH doses and FAST injection |
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What is the Cardiovascular effect of Ammonio steroids?
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They block Muscarinic receptors
PANCURONIUM block M2 receptors on heart causing moderate tachycardia In general, all muscle relaxants block Ach receptors in Autonomic ganglia and the heart if doses are high enough |
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What is the effect of Tubocurarine on Autunomic ganglia?
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It blocks Nicotinic receptors Nn of the Autonomic Ganglia due to loss of specificity for the Nm receptors only
This results in a fall in BP and Tacycardia |
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What is the Cardiovascular effect of Succinylcholine?
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Cardiac Arrythmias -still used due to short duration of action
In low doses - Negative Ionotropic and chronotropic responses occur In High doses - Positive Ionotropic and chronotropic responses may occur |
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Succinylcholine activates ...
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All Autonomic Cholinoceptors
Nicotinic - in both para and symp ganglia Muscarinic - in the heart It also has the ability to release Histamine IT DOES EVERYTHING |
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Which 2 non-dep NM blockers -Ammino steroids have NO effect on autonomic ganglia, M2 receptors?
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Vecuronium
Piperonium All other Ammonio steroids have NO effect on Autonomic ganglia,or Histamine release but.... Slight to Moderate block of M2 receptors |
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Which 2 non-dep NM blockers -Benzyl..have NO effect on autonomic ganglia, M2 receptors?
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Cisatracurium
Doxacurium All other Benzyl.. have NO effect on M2 receptors in the heart but..... Slight to moderate effect on Histamine release |
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Which 2 non-dep NM blockers -Benzyl have a weak blockade of autonomic ganglia?
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Tobucarine
Metocurine |
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Can these NM blockers cause loss of consciousness?
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NO- cannot cross BBB (quaternary cmpds)
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What are the AE assoc with Succinylcholine only?
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Hyperkalemia
Incr. intraoccular pressure Incr. intragastric pressure Muscle pain Malignant hyperthermia |
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How can the toxic effects of NM blockers be alleviated?
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Neostigmine - for Hypotension or Bronchospasm
Sympathomemetic amines may also be given Atropine or Glycopyrolate - to counteract muscarinic stimulation Antihistamines -to counteract effects of Histamine release ALL can be given together as a 'cocktail' |
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What r some drugs that ENHANCE NM blockade?
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Inhaled anesthetics
Local anesthetics Aminoglycosides - inhibit Ach release from the preganglionic terminal - via competition with Ca2+ Tetracyclines - via chelation of Ca2+ Some diseases can also ENHANCE NM blockade by Non-Dep agents Myasthenia gravis Advanced age |
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Depolarizing agents are antagonized by...?
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Non- depolarizing agents
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How do patients with severe burns respond to Non- depolarizing agents?
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They are Resistant
The same occurs in patients with Up Motor neuron disease |
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Give the uses of NM blockers..
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Surgical relaxant
Control of ventilation Treatment of convulsions - last resort Prevention of trauma during ECT - particularly Succinlycholine or Mivacurium due to short duration of action |
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Drugs used to treat Spasms are either grouped as...?
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Drugs for Chronic Spasm
Drugs for Acute spasm |
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Drugs for Chronic Spasm can act either ..?
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On the CNS
or On the Skeletal Muscle |
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Which Drugs for Chronic Spasm acts on the CNS?
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DIAZEPAM- Benzodiazepene, facilitates axn on GABA at GABA(a) Receptors
BACLOFEN -GABA agonist at GABA(b) receptors TIZANIDINE - Agonist of alpha 2 receptors in the CNS GABAPENTIN - Antiepileptic drug with promising spasmolytic effects and in patients with MS -Increase GABA release PROGABIDE -GABA(a) and GABA(b) GLYCINE - Inhibitory a.a Nt on spinal cord , active when given orally, readily crosses BBB |
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What r the 2 new agents for treatment of ALS?
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IDROCILAMIDE
RILUZOLE MOA- inhibitionof Gutamatergic transmission in the CNS |
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Which Drugs for Chronic Spasm acts on the Skeletal Muscle?
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*Dantrolene
Bind Ryanodine receptors in the SR of the skeletal muscle -interferes with the release of Ca2+ *Botulinum toxin -Treatment of Generalized spastic disorder e.g Cerebral Palsy |
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Which drug is used as an antidote in Malignant Hyperthermia?
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Dantrolene
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What r the drugs used for ACUTE spasms?
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Cyclobenzaprine -structurally related to TCAs
Most drugs are SEDATIVES or act on Spinal cord or Brain stem Strong antimuscarinic action Causes: Sedation Confusion Transient Visual Hallucinations |
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When is Cyclobenzaprine used?
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for relief of Acute muscle spasms caused by
Local trauma Sprain |
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Oh yes ..The end
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Yippeee
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