Katzung 12th ed - Chapter 26 - Local Anaesthetics (1)

Question 1

What is an easy way to remember which local anaesthetics are amides and which are esters?

Answer 1

Amides have two i’s in their name:
e.g. Lignocaine, Mepivacaine, Bupivacaine, Ropivacaine, Prilocaine
Esters have only one i in their name:
e.g. Cocaine, Procaine, Tetracaine.

Question 2

What is Xylocaine?

Answer 2

Xylocaine is the trade name for Lignocaine.

Question 3

What is Marcaine?

Answer 3

Marcaine is the trade name for Bupivacaine.

Question 4

Which local anaesthetic has the lowest potency?

Answer 4

Procaine.

Question 5

Which local anaesthetic has the shortest duration of action?

Answer 5

Procaine.

Question 6

Name three local anaesthetics with long durations of action.

Answer 6

Tetracaine, Bupivacaine, Ropivacaine.

Question 7

Describe the pharmacokinetics of ester-based local anaesthetics.

Answer 7

They have a rapid breakdown in plasma (elimination half-life is less than 1 minute) and thus have not been extensively studied.

Question 8

Pharmacokinetics of amide LA’s: Absorption. Describe how the administration of an amide LA together with adrenaline would affect the absorption.

Answer 8

Adrenaline is a vasoconstrictor, and therefore the resultant reduction in blood flow serves to reduce the rate of systemic absorption of amide LA and thus diminishes peak serum levels.

Question 9

How could ester-based local anaesthetics potentially accumulate in the bloodstream of a patient?

Answer 9

If the patient has reduced or absent plasma hydrolysis secondary to plasma cholinesterase deficiency.

Question 10

Where are the amide local anaesthetics metabolised?

Answer 10

Liver.

Question 11

Which amide local anaesthetic is the most rapidly metabolised?

Answer 11

Prilocaine.

Question 12

What are the approximate elimination half-lives of bupivacaine and ropivacaine?

Answer 12

Bupivacaine: 3.5hrs
Ropivacaine: 4.2hrs
They both have relatively slow hepatic metabolism.

Question 13

Pharmacodynamics: What is the primary mechanism of action of local anaesthetics?

Answer 13

Voltage-gated Sodium channel blockade.

Question 14

If Procaine has a potency of “1”, what is the potency of:

• Bupivacaine?
• Lignocaine?
• Cocaine?

Answer 14

• Bupivacaine: 16
• Lignocaine: 4
• Cocaine: 2

Question 15

What is a safe dose of lignocaine if given:

• IV?
• S/C?
• S/C with adrenaline?

Answer 15

• IV: 2mg/kg
• S/C: 3mg/kg
• S/C with adrenaline: 5mg/kg

Question 16

What is a safe dose of S/C bupivacaine?

Answer 16

2mg/kg

Question 17

What is a safe dose of intravenous regional anaesthesia (Bier’s block) using Prilocaine?

Answer 17

3-5mg/kg.

Question 18

Name four potential clinical uses for local anaesthetics.

Answer 18

Local anaesthesia.
Intravenous regional anaesthesia (Bier’s block)
Spinal anaesthesia.
Epidural anaesthesia.

Question 19

Describe some CNS toxicities of local anaesthetics.

Answer 19

Drowsiness, Visual and Auditory disturbances, Restlessness, Nystagmus, Shivering, Convulsions

Question 20

How do potassium levels affect the actions of local anaesthetics?

Answer 20

Hyperkalaemia will increase the effects of local anaesthetics.

Question 21

Describe some CVS toxicities of local anaesthetics.

Answer 21

Negative Inotrope. Decreased PVR. Reduced excitability and conduction.

Question 22

How are amide local anaesthetics metabolized and excreted?

Answer 22

Metabolized in the liver. Excreted in the urine.