Local Anaesthetics and Vasodilators

Question 1

Why are local anaesthetics used in dentistry?

Answer 1

Prevent pain feeling during procedures

Question 2

How is pain transmitted along a nerve fibre?

Answer 2

• Nociceptor detects stimulus
• Passes signal onto nerve cell until signal ends up in brain
• Sodium, potassium and calcium dependent

Question 3

What is the mechanism of local anaesthetics?

Answer 3

Block sodium channels

Question 4

Describe 2 ways in which local anaesthetics can block sodium channels

Answer 4

1. Membrane Expansion Theory - LA molecules become incorporated into cell membrane and swell to physically obstruct sodium channel
2. Specific Binding Theory - LA binds to receptor within sodium channel physically obstructing sodium channel

Question 5

What is the chemical structure of local anaesthetics?

Answer 5

Aromatic - Intermediate chain - Amine
lipophilic hydrophilic
portion portion

Question 6

What are 2 types of local anaesthetic?

Answer 6

1. Amino esters

2. Amino amides (mainly used)

Question 7

How are local anaesthetics named?

Answer 7

Dependent on the bond between the intermediate chain and aromatic lipophilic portion

Question 8

Name 4 amino amides used as local anaesthetics

Answer 8

1. Lignocaine
2. Mepivacaine
3. Articaine
4. Bupivacaine

Question 9

Which amino amide is used in theatre?

Answer 9

Bupivacaine as it is long lasting

Question 10

Name an amino ester used as local anaesthetic

Answer 10

Benzocaine used as topical anaesthetic

Question 11

Why are amino esters less used as local anaesthetic agents?

Answer 11

More likely to lead to hypersensitivity reactions

Question 12

How are amino esters metabolised?

Answer 12

Primarily metabolised by plasma esterases

Question 13

How are amino amides metabolised?

Answer 13

Usually occurs in the liver, with articaine being an exception and is metabolised by plasma esterases

Question 14

Name 5 factors which influence absorption of local anaesthetics

Answer 14

1. Type of drug used
2. Volume and concentration administered
3. Route of administration
4. Vascularity of tissues
5. Presence of vasoconstrictor

Question 15

How are local anaesthetics excreted?

Answer 15

Via kidney

Question 16

What are 3 reasons vasoconstrictors are added to local anaesthetics?

Answer 16

1. Longer lasting anaesthesia
2. More profound anaesthesia
3. Reduce operative bleeding

Question 17

What is the most commonly used vasoconstrictor?

Answer 17

Adrenaline

Question 18

Name 4 contents of a dental local anaesthetic cartilage (excluding the anaesthetic agent and vasoconstrictor)

Answer 18

1. Reducing agents
2. Preservatives
3. Fungicides
4. Ringer’s solution

Question 19

Why are reducing agents present in a dental local anaesthetic cartilage?

Answer 19

Prevent oxidation of adrenaline

Question 20

Name 4 causes of unwanted effects of local anaesthetics

Answer 20

1. Psychogenic effects
2. Local anaesthetic agent itself
3. Vasoconstrictor
4. Preservatives

Question 21

What 2 ways can a local anaesthetic agent cause unwanted side effects?

Answer 21

1. Toxicity

2. Drug interactions

Question 22

How can a preservative cause unwanted side effects during local anaesthetic?

Answer 22

Allergies

Question 23

What are 2 main problems when administering local anaesthetics?

Answer 23

1. Failure of anaesthesia

2. Injection into the wrong place

Question 24

Why can anaesthesia fail?

Answer 24

Acute infection can reduce effect of anaesthesia