local anesthetics

Question 1

local anesthetics chemical structure

Answer 1

lipophilic group (aromatic ring) + intermediate chain + ionizable group (tertiary amine)

Question 2

chemical properties of local anesthetics

Answer 2

ester links = prone to hydrolysis - shorter duration of action

cationic form = most active at receptor site

uncharged = penetrates biological membranes

Question 3

importance of ester links in local anesthetics

Answer 3

prone to hydrolysis

Question 4

importance of cationic form of local anesthetics

Answer 4

most active

Question 5

importance of uncharged form of local anesthetics

Answer 5

penetrates biological membranes

Question 6

how to enhance/lengthen duration of local anesthetics

Answer 6

vasocontrictors are given = usually EPI

dec systemic absorption by dec blood flow

dec systemic toxic effects

Question 7

EPI in spinal anesthesia

Answer 7

acts at alpha 2 = inhibit substance P

Question 8

cocaine as vasoconstrictor in local anesthetic

Answer 8

constricts BV by potentiating action of NE = preventing its own absorption

Question 9

what metabolizes ester linked anesthetics

Answer 9

tissue and plasma esterases: pseudocholinesterase

Question 10

what metabolizes/degrades amide linked local anesthetics

Answer 10

liver microsomal cytochrome p450

Question 11

MOA of local anesthetic

Answer 11

block VG sodium channels
bind to receptors near intracellular end of channel - block it

stop AP

Question 12

liposolubility vs toxicity in local anesthetics

Answer 12

greater liposolubility = grater toxicity

Question 13

pKa vs speed of onset

Answer 13

closer pKa to body pH, faster the onset

Question 14

procaine

Answer 14

short acting

Question 15

chloroprocaine

Answer 15

short acting

Question 16

lidocaine

Answer 16

intermediate acting

Question 17

mepivacaine

Answer 17

intermediate acting

Question 18

prilocaine

Answer 18

intermediate acting

Question 19

tetracaine

Answer 19

long acting

Question 20

bupivacaine

Answer 20

long acting

Question 21

etidocaine

Answer 21

long acting

Question 22

ropivacaine

Answer 22

long acting

Question 23

local anesthetic toxicity of CNS

Answer 23

restless, tremor = clonic convulsions

respiratory failure

premedication with benzo provides prophylaxis against seizures

Question 24

local anesthetic toxicity of CV

Answer 24

depress pacemaker activity, contractility

arteriolar dilation - hypotension

**cocaine can cause vasoconstriction and hypertension and arrhtymias

(bupivacaine is more cardiotoxic than others)

Question 25

toxicity in blood

Answer 25

prilocaine large doses == accumulate o-toluidine

o-toluidine = oxidizing agent capable of forming methemoglobin

Question 26

toxicity allergic reactions

Answer 26

ester types metabolize to PABA (p-aminobenzoic acid derivatives)

important for people allergic to PABA

BUT amides dont metabolize to PABA = no allergic reaction

Question 27

esters vs amides

Answer 27

esters = have 1 "i" 
amides = have 2"i"'s

esters = be careful of PABA allergy

Question 28

local anesthetic interactions

Answer 28

procaine -> PABA = inhibits action of sulfonamides

avoid in pt taking sulfonamides