QUIZ - Local Anaesthetics ANZCA Exam with verified detailed ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
answers
[Jul01] Lignocaine has a pKa of 7.9 At pH 6.9, the percentage ionised is:
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A. 1% (or 5%)
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B. 10%
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C. 50%
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D. 90%
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E. 99% - correct answer✔✔D
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Acids are predominantly ionised Above their pKa ; Bases are predominantly ionised Below
||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
their pKa ||\\//||
Lignocaine is a base, thus predominantly ionised in the pH in question ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
pH = pKA 50% ionised
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One unit away from pKa = 90% ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
Two units away from pKa = 99%.
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[Jul04] Cocaine: ||\\//||
A. Blocks reuptake of dopamine and noradrenaline
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B. Central effects are due to noradrenaline
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C. Crosses lipid soluble membranes because its pKa is 2.8
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D. Is not metabolised by plasma pseudocholinesterase
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E. Rapidly absorbed by nasal mucosa - correct answer✔✔A. Blocks reuptake of dopamine
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and noradrenaline - True for both - Cocaine's "euphoric properties are due primarily to
||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
, inhibition of catecholamine uptake, particularly dopamine, in the CNS." (Goodman and
||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
Gilman)
B. Central effects are due to noradrenaline - False: see A
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C. Crosses lipid soluble membranes because its pKa is 2.8 - False pKa 8.7
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D. Is not metabolised by plasma pseudocholinesterase - False "Ester-type local anesthetics
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are hydrolyzed very rapidly in the blood by circulating butyrylcholinesterase
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(pseudocholinesterase) to inactive metabolites." Katzung online ed. ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
E. Rapidly absorbed by nasal mucosa - not sure, definitely absorbed, but rapidly?
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[Mar03] Ropivacaine: ||\\//||
A. Produces greater motor block than bupivacaine
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B. Is prepared as the R enantiomer
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C. Is less lipid soluble than lignocaine
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D. Has the same cardiotoxicity as lignocaine - correct answer✔✔All false
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Ropivacaine
A. Is a pure R isomer
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B. Is an isomer of bupivacaine
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C. Provides more motor block than bupivacaine
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D. Has more toxicity than bupivacaine
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E. Has similar physico-chemical properties to bupivacaine - correct answer✔✔E
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Ropivacaine differs from bupivacaine mainly by: ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
A. More motor blockade than bupivacaine
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B. Mainly affecting A beta rather than A delta fibres
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C. Lower cardiac toxicity than bupivacaine
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answers
[Jul01] Lignocaine has a pKa of 7.9 At pH 6.9, the percentage ionised is:
||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
A. 1% (or 5%)
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B. 10%
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C. 50%
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D. 90%
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E. 99% - correct answer✔✔D
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Acids are predominantly ionised Above their pKa ; Bases are predominantly ionised Below
||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
their pKa ||\\//||
Lignocaine is a base, thus predominantly ionised in the pH in question ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
pH = pKA 50% ionised
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One unit away from pKa = 90% ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
Two units away from pKa = 99%.
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[Jul04] Cocaine: ||\\//||
A. Blocks reuptake of dopamine and noradrenaline
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B. Central effects are due to noradrenaline
||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
C. Crosses lipid soluble membranes because its pKa is 2.8
||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
D. Is not metabolised by plasma pseudocholinesterase
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E. Rapidly absorbed by nasal mucosa - correct answer✔✔A. Blocks reuptake of dopamine
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and noradrenaline - True for both - Cocaine's "euphoric properties are due primarily to
||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
, inhibition of catecholamine uptake, particularly dopamine, in the CNS." (Goodman and
||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
Gilman)
B. Central effects are due to noradrenaline - False: see A
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C. Crosses lipid soluble membranes because its pKa is 2.8 - False pKa 8.7
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D. Is not metabolised by plasma pseudocholinesterase - False "Ester-type local anesthetics
||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
are hydrolyzed very rapidly in the blood by circulating butyrylcholinesterase
||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
(pseudocholinesterase) to inactive metabolites." Katzung online ed. ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
E. Rapidly absorbed by nasal mucosa - not sure, definitely absorbed, but rapidly?
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[Mar03] Ropivacaine: ||\\//||
A. Produces greater motor block than bupivacaine
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B. Is prepared as the R enantiomer
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C. Is less lipid soluble than lignocaine
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D. Has the same cardiotoxicity as lignocaine - correct answer✔✔All false
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Ropivacaine
A. Is a pure R isomer
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B. Is an isomer of bupivacaine
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C. Provides more motor block than bupivacaine
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D. Has more toxicity than bupivacaine
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E. Has similar physico-chemical properties to bupivacaine - correct answer✔✔E
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Ropivacaine differs from bupivacaine mainly by: ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
A. More motor blockade than bupivacaine
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B. Mainly affecting A beta rather than A delta fibres
||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//|| ||\\//||
C. Lower cardiac toxicity than bupivacaine
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