Local Anesthetics - Pharmacology

Local Anesthetics- Pharm
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1. diff btw myelinated and unmyelinated2. myelinated= myelin covering interrupted by ____ which allow for passage of what?3. following peripheral nerve block, how much of drug reaches nerve? d/t what?4. 2 things that incr rate of conduction
1. unmyelinated= many axons- myelinated= 1 axon covered by many layers of schwann cell2. nodes of ranvier/ drugs and ions** also where neuronal excitation occurs**3. <2%- d/t many layers of connective tissue (inner to outer= endonerium, perineurium around bundle, epineurium)
1. "pain, temp, touch"- fast fibers2. "dull pain, temp, touch"- slow fibers3. diameter r/t speed?
1. A delta2. c fibers3. A fibers= larger diameterB fibers (sympathetic)= middle diameterC fibers = smaller diameter
Impulse Conduction1. na channels open. Na enters cell. potential reaches -65, what happens?**all or nothing event**2. how do local anesthetics work? they change what?
1. ALL Na channels open- Na rushes in. K begins to be pumped out (more slowly)2. they change the rate of depolarization. block Na channels- not enuf open to reach -65. No propagation of AP
1. how do highly lipophilic drugs work?- their effects?2. How do moderately lipophilic drugs work?- their effects?3. how do lipophobic drugs work?
1. cross into phospholipid bilayer and are sequestered or stuck. attached to "side" of Na channel from inside membrane-- slower onset but longer DOA; incr potency2. pass thru membrane quickly. become ionized. attach to Na channel from intracellular side. Fast onset.3. unable to pass thru lipid membrane
1. Closed/ resting Na channel= affinity for local anesth?2. affinity for open and inactivated Na channels?3. effect of drug staying at Na channel longer?
1. very low affinity2. higher affinity3. increased time before channel returns to resting conformation
1. blocksa. time btw action potentials exceeds time for dissociation of local anesthetic from Na channelb. time btw is too little for local anesthetic to dissociate --- gradual incr in # of channels blocked2. 2 ways in which "b" is produced
1. tonic blockb. phasic block2. (1) drug with high potency and high affinity (2) rapidly firing action potentials
1. susceptibility of various fibers to local anesthetic block2. two situations in which rate of fire is high or abnormal repetitive firing occurs
1. B fibers (symp, pregang) --> small myelinated A gamma and A delta **sensory - pain/ temperature** --> large myelinated Aa & Ab **motor**---> small, unmyelinated C fibers (dull pain)2. -- tissue injury or trauma-- various Dz such as neuropathic pain (may be treated with LocAn concentrations lower than necessary to block normal nerves)
1. how does differential block work?2. early detection of where block is going?3. chemistry= all local anesthetics have hydrophobic ______ joined to a hydrophilic ___-- they are all joined by 1 of which 2 bonds?
1. give small enuf doses of local anesthetic to see if pain is from sympathetic.. or a little more to see if it's sensory.. little more= motor2. sweating... 3. aromatic ringamineester or amide
1. 5 things that determine onset, duration and potency2. pka= lower?3. NET result in increased lipid solubility (3things)
1. pkalipid solubilityprotein bindingconcentrationvasoconstrictive/ vasodilatory properties2. lower with weak base= more lipophilic3. slower onset because it is sequestered in membrane- longer duration (d/t slow release of drug from lipid depot)- higher potency (higher Na channel affinity)
1. incr protein binding has what effect?2. incr dose/ concentration has what effect?3. vasodilators/ vasoconstrictors4. significant of vasodilation
1. incr DOA2. faster onset and longer DOA3. most are vasodilatorsexceptions: cocaine, ropivacaine, levobupivacaine.4. more vasodilation= drug will leave faster

1. addition of vasoconstrictors= decrs rate of what?-- results in what 2 things?2. effectiveness depends on what 2 things?3. most effective for what?4. most commons ones used?5. don't use where?
1. vascular absorption-- denser block- more drug reaches site of action-- longer duration- dcrs clearance2. type of drug and site of injection3. infiltration and peripheral nerve blocks with drugs of short to moderate duration (lido, mepivic)**not spinals/ epidurals**4. Epi- #1 (also NorEpi, Phenylephrine)5. sites that may experience vascular compromise (finger, penile)
1. pH adjustment?2. technique?3. of particular value with what?
1. alkalinization - more unionized - faster onset - greater depth - incr spread of epidural block - less burning than acidic solution2. add 1ml sodium bicarb to 10ml local3. prepackaged local with epi (pH is lower)
1. toxicity should be presumed to be ____- don't assume u can give max doses of multiple drugs2. binding of Na channel PRIMARILY occurs how?3. rapidly conducting fibers are more susceptible to LA block d/t what?
1. additive2. intracellular side3. phasic inhibition occuring as a result of increased conduction velocity
1. lower pKa2. incr lipid solubility3. incr protein binding4. incr concentration5. incr dose6. incr vasodilatory properties
1. more un-ionized-> faster onset2. incr duration, incr potency3. incr duration4. faster onset5. incr duration6. shorter duration
1. injection of local anesthetic into infected (acidotic tissue)
1. relatively ineffective
Procaine1. brand name/ class2. signif3. derivative of ___ = result?4. pka, solubility, onset, DOA5. high incidence of ___ and ___**rarely used anymore**
1. novacaine/ ester2. 1st injectable LA3. PABA- allergic reactions4. high pka, low lipid sol, slow onset, short DOA5. nausea and allergic rxns
chloroprocaine1. brand/ class2. derivative of what?3. signif?4. primarily used for what?5. controversery regarding what?6. disadvantage?
1. nesacaine/ ester2. procaine3. most rapidly metabolized (plasma T1/2 30sec)4. as epidural anesthetic for c section5. neurotox in SAS6. reduces analgesic effect of bupiv or other opioids
Tetracaine1. brand/ class2. used primarily - 2 things?3. duration?4. solubility?5. protein binding?6. metabolism7. potency8. profound ___ and ___ block9. supplied as what? allows for what?
1. pontocaine/ ester2. topical (eye) and spinal anesthesia3. long4. highly lipid sol5. high 6. slow7. high8. sensory and motor9. crystalline form- allows for variability in baricity(hypobaric goes up in CSF)
Benzocaine1. brand/ class2. unique?3. best suited for what?4. onset?5. duration6. disadvantage- potential to produce what?
1. hurricane/ ester2. weak acid (pka 3.5)3. topicalization of mucous membranes- endoscopy- bronchoscopy- fiberoptic intubation- cetacaine spray4. extremely rapid5. 30-60min6. methemoglobinemia
Cocaine1. class2. produces intense ____3. used for what?4. low __ __; high ___ ___
1. ester2. vasoconstriction3. 4% or 10% sol'n for nasopharyngeal topical4. therpeutic index/ abuse potential
Lidocaine1. brand/ class2. signif3. onset4. DOA5. uses? (IM Losing Some Brain In A Night)
1. xylocaine/ amide2. 1st aminoamide introduced/ most widely used3. rapid onset4. intermediate DOA5. InfiltrationMucous Membranes (in combo with vasoconstrictor)Liposuction (tumescent- large volumes of dilute anesthetic prior to surgery)Spinal - central neuraxis anesthesia (epidural/ spinal)Beir Block (regional anesthetic)Intubation (blunts hemodyn response)Anti-dyrhythmicNeuropathic pain (chronic)= low doses effective in blocking ectopoic discharges possibly thru inhibition of hippocampal and thalamic nerves
Mepivacaine1. brand/ class2. very similar to ____3. minor difference4. similar incidence of what?5. useful in what?6. poorly metabolized by ___= accumulation may lead to poor ___ ___
1. carbacaine/ amide2. lidocaine3. slightly longer DOA since less vasodilation4. TNS (transient neuro. symptoms)5. peripheral nerve blocks6. fetus/ muscle tone
Prilocaine1. brand/ class2. very similar to ___3. three exceptions?4. most commonly used how?5. large doses- the metabolite orthotoludine can accumulate and produce what?
1. citanest/ amide2. lidocaine3. slightly longer DOA d/t less vasodilationdcrs CNS toxmore rapidly metabolized4. with lidocaine in EMLA cream5. methemoglobinemia
Bupivacaine1. brand/ class** 3 uses **2. onset (with what 2 exceptions?3. DOA4. concentrations below 0.25%, ___ block is greater than ___ block5. good for what 2 things?6. disadvantage?7. most commonly used ________a. onsetb. duration8. Epidurala. extremely versatile in ___ depending on depth of anesthesia neededb. result of lower concentrationc. do not use __% d/t potential for what?9. 2 types of peripheral nerve block10. what is extremely important to remember?11. not used for what?
1. Marcaine/ amide** spinal, epidural, peripheral nerve block**2. slower (except in spinals/ infiltration anesth)3. long4. sensory/ motor5. post-op pain, labor analgesia6. selective cardiotoxicity 7. spinal anesthetica. 5min rapid)b. dose-dpendent8. concentrationsb. more sensory than motor blockc. 0.75%/ cardiac toxicity9. brachial plexus and 3 in 110. incremental dosing injections11. regional/ beir blocks (d/t tox concerns)
Ropiviacaine1. brand/ class2. similar to ___3. differences4. unique aspect
1. Naropin/ amide2. bupivacaine3. may produce less motor block- less cardiac/ neuro toxicity effects4. causes mild vasoconstriction
LevoBupivacaine1. Brand/ class2. _____ of bupiv.3. similar to bupiv but with what diff?4. advantage?5. advantages of Ropiv/ Levobupiv appear limited to which type of blocks?
1. chirocaine/ amide2. S-enantiomer3. possibly slightly longer DOA4. less cardiac/ neruo toxicity5. where large volume of local anesthetic is required
1. ___ of LA varies with application2. good drug for peripheral nerve block3. good drug for spinal
1. potency2. mepivacaine3. bupivacaine
Infiltration Anesthesia1. most LA effective2. two most commonly used3. concentration?4. do what to reduce burning?
2. bupivacaine and lidoc3. effective at low concentrations4. addition of neutracaine (sodium bicarb)
Beir Block1. most common drug used= concentrations/ amt used fora. armb. leg2. using ester local anesthetics may result in what?
1. Lidocaine WITHOUT EPIarm- 40-50ml of 0.5% sol'nleg 50-100ml of 0.25%2. thrombophlebitis
Peripheral Nerve Blocks1. diff btw major and minor2. drug of choice?
1. minor - single nervemajor- all others2. determined by required duration of block
Epidural Anesthesia1. single shot techniques (caudal in children)- what is important?2. catheter techniques- what's important?3. Epi produces incr DOA with which LA?4. low concentrations of Bupiv has what effect?5. signify of chloroprocaine
1. DOA2. speed of onset, characteristics more important3. shorter/ interm acting drugs4. more sensory than motor block5. dcrs effectiveness of concurrent bupivacaine or opioids

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