9. Types of local anesthetics and their metabolism. Mechanism of action of local anesthetics. Vasoconstrictors. Interaction of local anesthetics with other drugs .

Question 1

Purpose of LA

Answer 1

-Pain control

Question 2

Method of action of Local anaesthetics

Answer 2

• Block voltage gated sodium channels
• Block depolarisation of cell and inhibit neural activity

Question 3

Structure of sodium channel

Answer 3

• Alpha 1 (pore through which sodium enters)
• Beta 1
• Beta 2

Question 4

Number of variations of sodium channel

Answer 4

-9 different variations

Question 5

Techniques of local Anaesthesia

Answer 5

• Topical
• Infiltration
• Regional block
• Intraosseous
• Intraligamentary
• Intrapulpal

Question 6

Two types of local anaesthetics

Answer 6

• Esters
• Amines(mostly used)

Question 7

Differences between esters and amines

Answer 7

• In metabolism and allergy production
• Esters metabolised in plasma
• Amines primarily undergo hepatic metabolism (prilocaine breakdown also in lungs, articaine metabolism in plasma)

Question 8

Lidocaine

Answer 8

• Gold standard
• Plain solution of 2%-> short lasting

-Epinephrine vasoconstrictor common 1:200 000 to 1:80 000(5μg/m to 12.5μg/m)

Question 9

Mepivicaine

Answer 9

-Concentration of 2% 1:100 000 epinephrine→ similar to 2% epinephrine lidocaine

3% plain (better anaesthesia than lidocaine when vasoconstrictor free solution required)

Question 10

Prilocaine

Answer 10

• 4% plain solution
• 3% solution w/ vasocontrictor felypressin(if epinephrine free required)

Question 11

Formulations of topical anesthetics

Answer 11

• Creams
• Ointments
• Sprays

Question 12

Local anaesthetics agents commonly used as topical

Answer 12

• Lidocaine and Benzocaine
• Oraqix-Lidocaine and prilocaine

Question 13

Technique for infiltration anaesthesia

Answer 13

• Mouth partly open
• Needle to depth of buccal sulcus(if bone contacted-slight withdrawal)
• Injection site supraperiosteal
• Aspiration and injection of 1-2 ml

Question 14

Benefits of slow injection

Answer 14

• Reduces discomfort
• Increases success
• Lessens systemic problems

Question 15

How long do infiltration injections last?

Answer 15

Pulps 45 mins and soft tissues 1.5-2 hours

Question 16

Anaesthetic used in those allergic to amides

Answer 16

Procaine

Question 17

Amide metabolised in plasma and therefore has shorter half life and is safer

Answer 17

Articaine

Question 18

Articaine

Answer 18

4% 1:100 000 or 1:200 000 epinephrine

-Better mandibular infiltration anaesthesia than lidocaine

Question 19

Bupivacaine

Answer 19

• long lasting
• 1:200 000
• Supplementary intraoral injection during general anaesthesia
• Reduces number of post-op analgesics required

Question 20

Effect of Epinephrine in La

Answer 20

🔹Vasoconstriction
🔹Reduced bleeding
🔹Prolonged anaesthesia

Question 21

Effects of Epinephrine injection into vessel

Answer 21

🔷Systemic absorption-systemic toxicity
🔹Cardiovascular effects- tachycardia , Hypertension, arrhythmias
🔹CNS effects- dizziness, tremors, seizures
🔹Local tissue ischemia->necrosis

Question 22

Epinephrine effect on heart

Answer 22

🔹Secreted by adrenal glands
🔹Binds to beta adrenergic receptors on heart muscle cells
🔹Increases HR and strength of contractions->increased blood supply
🔹Raises Bp

Question 23

Role of epinephrine in allergic reactions

Answer 23

🔸Inhibits release of inflammatory mediators
🔸Histamine, leukotrienes

Question 24

How epinephrine counteracts effects of vasodilation and increased vascular permeability during allergic reactions

Answer 24

🔸Induces vasoconstriction and reduces vascular permeability

Question 25

Importance of bronchodilation during severe allergic reactions

Answer 25

🔸Improved airflow

Question 26

Effects epinephrine has on cardiovascular system during allergic reactions

Answer 26

🔸Maintains blood pressure and cardiac output

Question 27

How Articaine has better penetration into tissues than lidocaine

Answer 27

🔸Presence of ester group in its structure
🔸Allows better diffusion

Question 28

Advantages of Articaines improved penetration

Answer 28

🔸More profound anaesthesia at lower doses

Question 29

Main effects of epinephrine in allergy

Answer 29

🔸Vasoconstriction (reduces swelling)
🔸Bronchodilation (improved airflow)
🔸Cardiovascular effects
🔸Suppression of inflammatory mediators

Question 30

Active ingredient of Ubistein

Answer 30

Articaine and epinephrine

Question 31

Active ingredient of Scandonest

Answer 31

Mepivicaine and epinephrine

Question 32

Active ingredient of xylodren

Answer 32

Lidocaine and epinephrine

Question 33

Active ingredient of dentocain

Answer 33

Articaine and adrenaline

Question 34

Active ingredient of septonest

Answer 34

Adrenaline and Articaine

Question 35

Factors that affect intensity and duration of LA’s

Answer 35

🔸Tissue blood flow
🔸Activity of plasma cholinesterase
🔸Vasoconstrictor use
🔸pH of tissue
🔸Dose of La

Question 36

How infection hinders effect of La

Answer 36

🔸Creates acidic environment->decreases pH of tissues
🔸Alters ionisation and ability to penetrate nerve fibres->
🔸Reduces the potency and duration of LAs

Question 37

Strategies to overcome resistance of LA in infected tissues

Answer 37

🔸Antibiotics and anti inflammatory agents (reduce inflammation and acidity)
🔸Regional nerve blocks and intravenous sedation

Question 38

Overdose of LAs can cause

Answer 38

🔹Severe hypotension (Vasodilation)
🔹Seizures
🔹Respiratory depression