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45 Cards in this Set
- Front
- Back
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local vs. global
anesthetics |
local anesthetics – the faster it’s absorbed, the faster it quits working
global anesthetics – the faster it’s absorbed, the faster it starts working |
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2 types of local anesthetics
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esters
amides |
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ester
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1 "i" in name
has carbonyl group (C dbl bond O) between the aromatic (benzene ring) group [lipid soluble - hydrophobic] and the tertiary amine group [water soluble - hydrophilic] Where most allergic reactions occur |
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name esters
generic & Brand names) |
cocaine
procaine (Novocaine) chloroprocaine (Nesacaine) tetracaine (Pontocaine) |
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metabolization of esters
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cholinesterase
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cholinesterase
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metabolizes ester local anesthetics
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cocaine
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ester
max safe dose - 200mg TOPICAL unique properties: causes vasoconstriction – facilitates nasal surgery b/c it results in shrinking the mucosa; produces vasoconstriction by blocking norepi & epi uptake into the adrenergic nerve ending. |
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procaine
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ester
brand name - Novocaine max safe dose - 14mg/kg maximum single dose for infiltration in adult – 500mg pKa 8.9 duration – 45-60mins |
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chloroprocaine
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ester
brand name - Nesacaine max safe dose - 20mg/kg maximum single dose for infiltration in adult – 600mg pKa – 8.7 – the exception to the pKa onset rule – it’s the fastest onset duration – 30-45min |
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tetracaine
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ester
brand name - Pontocaine max safe dose - 1mg/kg maximum single dose for infiltration in adult – 100mg - TOPICAL pKA – 8.5 duration – 60-180min |
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Novacaine
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ester
generic name - procaine max safe dose - 14mg/kg |
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Nesacaine
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ester
generic name - chloroprocaine max safe dose - 20mg/kg |
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Pontocaine
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ester
generic name - tetracaine max safe dose - 1mg/kg |
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amide
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2 "i"s in name (except benzocaine)
has C dbl bond N between the aromatic (benzene ring) group [lipid soluble - hydrophobic] and the tertiary amine group [water soluble - hydrophilic] Very, very rare to have allergic reaction Can be more toxic – must be metabolized in the liver making it longer acting |
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name amides
generic & (Brand names) |
lidocaine (Xylocaine)
levobupivacaine (Chirocaine) etidocaine (Duranest) ropivacaine (Naropin) bupivacaine (Marcaine, Sensorcaine) articaine (Septocaine) mepivacaine (Carbocaine, Polocaine) benzocaine |
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metabolization of amides
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occurs in liver with hepatic microsomal enzymes
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hepatic microsomal enymes
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metabolizes amides in the liver
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lidocaine
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amide
Brand name – Xylocaine max safe dose – 7mg/kg maximum single dose for infiltration in adult – 300mg pKa – 7.9 duration – 60-120min |
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levobupivacaine
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amide
Brand name – Chirocaine max safe dose – 3mg/kg isomer of bupivacaine without the cardiac effects |
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etidocaine
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amide
Brand name – Duranest max safe dose – 3mg/kg maximum single dose for infiltration in adult – 300mg pKa – 7.7 duration – 240-180 amide Brand name – Naropin max safe dose – 3mg/kg chiral – molecule possesses an asymmetric carbon atom isomer of bupivacaine without the cardiac effects maximum single dose for infiltration in adult – 200mg pKa – 8.1 duration – 240-480min amide Brand name – Marcaine, Sensocaine max safe dose – 3mg/kg chiral – molecule possesses an asymmetric carbon atom maximum single dose for infiltration in adult – 175mg pKa – 8.1 duration – 240-480min Cardiotoxic – has special affinity for binding to cardiac proteins; first sign is cardiac arrest, may last for ≈ 2hrs even with resuscitation; can reverse by giving intralipid, drug will bind to it rather than cardiac receptors Only occurs with bupivacaine amide Brand name – Septocaine max safe dose - ? amide Brand name – Carbocaine, Polocaine max safe dose – 7mg/kg chiral – molecule possesses an asymmetric carbon atom maximum single dose for infiltration in adult – 300mg pKa – 7.6 duration – 90-180min amide Brand name – none max safe dose - ?, topical amide generic name – lidocaine max safe dose –7mg/kg amide generic name – levobupivacaine max safe dose – 3mg/kg amide generic name – etidocaine max safe dose – 3mg/kg amide generic name – ropivacaine max safe dose – 3mg/kg |
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ropivacaine
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amide
Brand name – Naropin max safe dose – 3mg/kg chiral – molecule possesses an asymmetric carbon atom isomer of bupivacaine without the cardiac effects maximum single dose for infiltration in adult – 200mg pKa – 8.1 duration – 240-480min |
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bupivacaine
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amide
Brand name – Marcaine, Sensocaine max safe dose – 3mg/kg chiral – molecule possesses an asymmetric carbon atom maximum single dose for infiltration in adult – 175mg pKa – 8.1 duration – 240-480min Cardiotoxic – has special affinity for binding to cardiac proteins; first sign is cardiac arrest, may last for ≈ 2hrs even with resuscitation; can reverse by giving intralipid, drug will bind to it rather than cardiac receptors Only occurs with bupivacaine amide Brand name – Septocaine max safe dose - ? amide Brand name – Carbocaine, Polocaine max safe dose – 7mg/kg chiral – molecule possesses an asymmetric carbon atom maximum single dose for infiltration in adult – 300mg pKa – 7.6 duration – 90-180min amide Brand name – none max safe dose - ?, topical amide generic name – lidocaine max safe dose –7mg/kg amide generic name – levobupivacaine max safe dose – 3mg/kg amide generic name – etidocaine max safe dose – 3mg/kg amide generic name – ropivacaine max safe dose – 3mg/kg |
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cardiotoxic effect
of bupivacaine |
Cardiotoxic – has special affinity for binding to cardiac proteins; first sign is cardiac arrest, may last for ≈ 2hrs even with resuscitation; can reverse by giving intralipid, drug will bind to it rather than cardiac receptors
Only occurs with bupivacaine |
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articaine
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amide
Brand name – Septocaine max safe dose - ? |
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mepivacaine
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amide
Brand name – Carbocaine, Polocaine max safe dose – 7mg/kg chiral – molecule possesses an asymmetric carbon atom maximum single dose for infiltration in adult – 300mg pKa – 7.6 duration – 90-180min |
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benzocaine
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amide
Brand name – none max safe dose - ?, topical |
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Xylocaine
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amide
generic name – lidocaine max safe dose –7mg/kg |
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Chirocaine
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amide
generic name – levobupivacaine max safe dose – 3mg/kg |
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Duranest
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amide
generic name – etidocaine max safe dose – 3mg/kg |
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Naropin
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amide
generic name – ropivacaine max safe dose – 3mg/kg |
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Marcaine
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amide
generic name – bupivacaine max safe dose – 3mg/kg |
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Sensorcaine
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amide
generic name – bupivacaine max safe dose – 3mg/kg |
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Septocaine
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amide
generic name – articaine max safe dose – ? mostly dental |
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Carbocaine
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amide
generic name – mepivacaine max safe dose – 7mg/kg |
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Polocaine
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amide
generic name – mepivacaine max safe dose – 7mg/kg |
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Misc LA
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Emla cream, others
Hyaluronidase (Wydase, Vitrase |
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LA access to Na+ channels
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Except for benzocaine, all LA work from inside the nerve. The ionized and non-ionized portions of the drug equilibriate outside the nerve, the non-ionized portion, lipid soluble part, enters the nerve through the lipid barrier, re-equilibriates with the ionized portion in the axoplasm and the ionized fraction (LA+) attaches to the local anesthetic receptor in the sodium channel.
Benzocaine only works topically and acts from the outside of the nerve to block Na+ channels. |
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Mechanism of action
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By blocking open Na+ channels, LA work to prevent initiation of an action potential by keeping the channels from returning to the resting or repolarized state.
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LA distribution
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Amides – the LA is injected thru the skin & equilibrates into nonspecific tissue binding, nerve blockage & blood stream uptake & removal – these states are interchangeable. From the blood stream there can be systemic tissue distribution or transport to the liver. In the liver there is hepatic metabolism or plasma hydrolysis followed by renal excretion.
Esters – mostly metabolized by cholinesterase at the injection site, then systemically. |
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LA with Epi
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When epi is added to a LA (vasoconstriction decreases removal of drug from site):
onset time decreases** degree of motor blockade increases degree of sensory blockade increases duration of blockade increases area of blockade increases peak plasma concentration decreases **during spinal anesthesia, epi will delay onset of action larger dose of drug – gives faster onset, but increases peak plasma concentration DO NOT INJECT around end-arteries (fingers, toes, ear, nose or penis – could result in adrenergic stimulation Use caution with cocaine – could cause toxic effect of epi & result in life-threatening ventricular arrhythmias |
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pKa
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primary determinant of onset of action
the closer to physiologic pH, the faster the onset the higher the pKa, the less ionized the drug is so it is less able to penetrate the nerve |
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Ion trapping
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occurs in 5 ways:
1. overdose with hypoxia 2. fetal pH lower than maternal pH 3. acidic conditions of infected tissues 4. carbonation of LAs 5. addition of NaHCO3 to LAs |
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ion trapping
overdose with hypoxia |
in overdose (or when given vascular), drug moves across BBB to brain. The associated respiratory depression results in hypoxia and acidosis.
The acidosis may increase the ionized fraction (the water soluble part) that can’t cross the lipid-rich BBB to leave the brain and reenter the systemic circulation. May prolong and enhance the CNS toxicity of Las In case of OD – don’t let pt get hypoxic – give O2 |
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ion trapping
fetal pH lower than maternal pH |
mom’s pH ≈ 7.4, fetal pH ≈ 7.2
LA crosses placenta in non-ionized form, d/t lower fetal pH LA ionizes resulting in LA accumulation in the fetal circulation giving high fetal levels of LAs The more acidic the fetal circulation, the greater the accumulation of the LA |
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ion trapping
acidic conditions of infected tissues |
infected tissue is acidotic with pH ≈ 5-6
rendered ineffective d/t loss of lipid solubility & is 100% ionized |
