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Winter Exam #4 - NMJ Blockers & Local Anesthetics
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32
Pharmacology
Graduate
02/16/2010

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Term
dantrolene [Dantrium]
Definition
causes muscle relaxation;
Uses: malignant hyperthermia, long-term control of muscle spasms
SEs: muscle weakness, hepatotoxicity
Term
botulinum toxin [Botox]
Definition
used to tx blephorospasm (involuntary eyelid closing), strabismus (eye spasms), and wrinkle treatment
SEs: upregulation of post-synaptic nicotinic ACh receptors at previous injection site; eyelid droop (ptosis)
Term
Paralysis characteristics of NMJ blockers
Definition
small rapid moving muscles first --> then limb trunk muscles --> then intercostal muscles --> lastly, diaphragm
Term
Side Effects of Non-depolarizing NMJ Blockers
Definition
prolonged apnea, histamine release (bronchospasm, hypotension)
Term
sugammadex [Bridion]
Definition
drug that binds steroidal NMJ blockers in a dose-dependent manner to encapsulate & inactivate steroidal NJM blockers like rocuronium within minutes; encapsulated drug complex is then eliminated via kidney filtration
Term
mivacurium [Mivacron]
Definition
non-depolarizing NMJ blocker with shortest duration of action;
Onset: 2-4 min
Metabolized in PLASMA by butyrylcholinesterase
Term
rocuronium [Zemuron]
Definition
newer non-depolarizing NMJ blocker with INTERMEDIATE duration of action;
Onset: 1-2 min;
Duration: 30-60 min
Term
vecuronium [Norcuron]
Definition
non-depolarizing NMJ blocker with intermediate duration of action;
Onset: 2-4 min;
Duration: 60-90 min
Term
atracurium [Tracrium], cisatracurium [Nimbex] (3x more potent than atracurium)
Definition
non-depolarizing NMJ blockers with intermediate duration of action;
Onset: 2-4 min
Duration: 30-90 min
NOT metabolized by enzymes;
degraded by temp. & pH-dependent Hofmann rxn
Term
pancuronium [Pavulon]
Definition
steroidal non-depolarizing NMJ blocker; 2nd drug used in lethal injection protocol behind sodium pentathol;
Onset: 4-6 min
Duration: 120-180 min
Term
succinylcholine [Anectine]
Definition
depolarizing NMJ blocker;
Duration: 5-8 min;
Time to onset: 1-1.5 min;
Uses: very short procedures (i.e. intubation);
Initial fasciculations --> chest & abdomen mostly; NO ANTIDOTE;
MoA: excessive opening of ACh receptors --> decreased electrochemical driving forces --> less positive ion entry --> less muscle response to motor neuron activity;
SEs: malignant hyperthermia, muscle soreness, histamine release, sinus bradycardia, prolonged muscle depolarization (hyperkalemia, cardiac arrest);
Phase I: fast onset, only a single dose required, neostigmine augments blocking action;
Phase II: occurs after prolonged infusion or high dose (10x normal dose), slow onset, neostigmine antagonizes drug block
Term
Local Anesthetics (LAs)
Definition
1) lipophilic domain allows entry into neuronal axon;
2) intermediate chain determines degree of metabolism - amides = long-acting, esters = short-acting;
3) hydrophilic N terminal or domain determines inhibitory action at Na channel
Term
epinephrine
Definition
co-administer with LAs to double duration of action & reduce amount of LAs by 1/3rd;
SEs: gangrene at small, peripheral sites
Term
field block anesthesia
Definition
subcutaneous injection of LA to numb sites distal to injection site
Term
nerve block anesthesia
Definition
inject peripheral nerves or plexus; requires less LA for this type of anesthesia
Term
intravenous regional anesthesia
Definition
injection of LA into vein of limb with tight tourniquet to occlude blood flow; whole limb is affected; surgery must be finished within 2 hrs due to tourniquet pain & time allowed to be in a tourniquet
Term
epidural block
Definition
injection into space within vertebral canal but superficial to dural sac
Term
spinal block
Definition
injection into CSF in subarachnoid space
Term
Advantages of Spinal Block
Definition
less time; less discomfort; less LA is needed; more intense sensory & motor block; correct placement of needle can be confirmed with CSF; Limited to injection sites below termination of spinal lumbar cord (2nd lumbar vertebra)
Term
Advantages of Epidural Block
Definition
NOT limited to injection sites below termination of spinal cord;
less risk for post-dural puncture HA;
placement of catheter for long-term pain reduction;
fine tune anesthesia by varying dose of LA into catheter
Term
Ester LAs - procaine, tetracaine, benzocaine, cocaine
Definition
LAs metabolized in plasma --> metabolized too fast to be redistributed at low doses
Term
Amide LAs - lidocaine, bupivicaine, prilocaine, dibucaine
Definition
LAs that are taken up by fat, brain, kidney, liver, then muscle & gut; highly protein bound; metabolized in liver
Term
CNS Side Effects of LAs
Definition
Low conc.: sleepiness, dizziness, restlessness;
High Conc.: nystagmus, shivering, CNS depression, respiratory failure --> death, restlessness & tremor --> tonic-clonic convulsions (tx with barbiturates or benzodiazepines IV)
Term
Cardiovascular Side Effects of LAs
Definition
minimimal changes in electrical excitability, conduction rate, force of contraction;
Higher, toxic levels: depression of cardiac excitability --> cardiovascular collapse, death;
vasodilators
Term
lidocaine
Definition
amides; most widely used LA;
Uses: infiltration, nerve block, spinal, epidural, topical, & IV;
Usually administered with Epi --> increased length of anesthesia;
Term
bupivicaine [Marcaine, Sensorcaine]
Definition
amide LA;
long duration of action;
Uses: infiltration, nerve block, spinal, epidural
NOT RECOMMENDED for IV use;
CARDIOTOXIC
Term
prilocaine (Citanest)
Definition
similar to lidocaine; amide LA;
most often used for infiltration anesthesia in DENTISTRY
Term
dibucaine (Nupercainal)
Definition
amide LA; topical application to skin &/or mucosal membranes; NOT used in USA
Term
procaine (Novocain)
Definition
ester LA;
Uses: infiltration, nerve block, spinal, epidural, topical, & IV;
Slower onset of action;
Onset of action: 2-5 min;
Duration: 1 hr
Term
tetracaine [Pontocaine]
Definition
ester LA;
MOST common LA for spinal anesthesia;
NOT recommended for any administration form;
Slow onset, toxicity, metabolism is SLOW;
10x more toxic than procaine
Term
benzocaine [Americaine, Hurricaine, Chloraseptic]
Definition
ester LA;
used TOPICALLY for skin;
toxicity due to methemoglobin production (rare);
poorly water soluble; NOT well absorbed;
LOW TOXICITY
Term
cocaine HCl
Definition
ester LA; topical use only;
well absorbed via mucuous membranes;
vasoconstrictor (only LA for this);
Toxicity: nervousness, tonic-clonic seizures, cardiac failure;
DO NOT give with Epi --> increases cardiac toxicity
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