12- Local Anesthetics

Question 1

bupivacaine (Sensorcaine)

Answer 1

amide LA
-long duration (longer with Epi added)
-slower onset; longer, variable duration (2-3 hrs spinal, 12-24 hrs peripheral block)
-CARDIOTOXIC
++results from cumulative doses, diffacult to dissoc. from Na+ channels
-metabolized hepatically (blood flow important)
-diluted conc. for peripheral blocks and careful use in OB

Question 2

etidocaine (Duranest)

Answer 2

amide LA

• longer duration (onset like lido, duration like bupivacaine)
• alkyl substitution between amine and amide inc. lipid solubility and DOA
• metabolized hepatically (blood flow important)
• Downside: prolonged motor blockade that outlasts sensory
• not useful for peripheral blocks

Question 3

lidocaine (Xylocaine)

Answer 3

amide LA

• rapid absorption parenteral, GI and resp.
• intermediate duration
• metabolized hepatically (blood flow important)
• 1.5-2% for most regional blocks for surgery
• more dilute concen. for pain management

Question 4

mepivacaine (Carbocaine)

Answer 4

amide LA

• intermediate duration (pharma similar to lido)
• similar onset, slightly longer DOA (3-6 hrs)
• metabolized hepatically (blood flow important)
• toxic to neonates so not used in OB

Question 5

prilocaine (Emla)

Answer 5

amide LA
-intermediate duration (pharma similar to lido)
-lacks vasodilation, has inc. Vd, limits CNS toxicity
-metabolizec hepatically (blood flow important)
-causes methaglobinemia (at ~8mg/kg)
++treat with methylene blue (1-2mg/kg)
-not used often peripherally

Question 6

ropivacaine (Naropin)

Answer 6

amide LA

• single enantiomer of bupivacaine (lower toxicity)
• slower uptake, thus lower blood levels
• extensive hepatic metabolism
• less potent then bupiva. at lower concentrations and at higher concentrations, dense block has shorter DOA
• at 0.75%, onset fast, CNS and cardiotoxicity reduced, motor block less then bupivacaine
• popular in peripheral blocks

Question 7

amide

Answer 7

• metabolized by liver

- amide linkage connects the aromatic ring to the tertiary amine

Question 8

enantiomers

Answer 8

chiral molecules that are mirror imagines of each other

-molecules are not superimposable on each other

Question 9

anesthesia

Answer 9

• amnesia
• unconsciousness
• skeletal muscle relaxation
• reduction of autonomic responses

Question 10

ester

Answer 10

-metabolized by pseudocholinesterase
-ester linkage connects aromatic ring to the tertiary amine
cocaine, procaine, chloprocaine, tetracaine

Question 11

lipid solubility

Answer 11

dissolves in fatty solutions, insoluble in water

affects drug absorption and distribution

Question 12

neurotoxicity

Answer 12

toxic substances that alters the normal activity of the nervous system in such a way that can cause damage.

Question 13

potency

Answer 13

measure of drug activity expressed in terms of the amount required to produce an effect of given intensity

Question 14

methemoglobinemia

Answer 14

blood disorder in which an abnormal amount of methemoglobin is produced

• unable to release oxygen as effectively to the body tissues
• caused by prilocaine

Question 15

benzocaine

Answer 15

ester local anesthetic

• metabolized by pseudocholinesterase
• “allergy” to LA is actually due to additive PABA

Question 16

procaine

Answer 16

ester local anesthetic

• metabolized by pseudocholinesterase
• 1st synthetic LA
• slow onset; short DOA (not used much)
• “allergy” to LA is actually due to additive PABA
• DOA: 45-60”

Question 17

cocaine

Answer 17

ester local anesthetic

• hepatic metabolism
• block local NE reuptake (vasoconstriction).
• euphoria 2/2 blocking of DA reuptake in CNS.
• Mainly used in nasal passages to provide LA as well as vasoconstriction.

Question 18

tetracaine

Answer 18

ester local anesthetic

• metabolized by pseudocholinesterase
• longest duration ester LA
• toxic for use in peripheral nerve blocks.
• spinal may last 6-8’
• “allergy” to LA is actually due to additive PABA
• DOA: 60-180”