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

1
Q

Purpose of LA

A

-Pain control

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2
Q

Method of action of Local anaesthetics

A
  • Block voltage gated sodium channels
  • Block depolarisation of cell and inhibit neural activity
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3
Q

Structure of sodium channel

A
  • Alpha 1 (pore through which sodium enters)
  • Beta 1
  • Beta 2
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4
Q

Number of variations of sodium channel

A

-9 different variations

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5
Q

Techniques of local Anaesthesia

A
  • Topical
  • Infiltration
  • Regional block
  • Intraosseous
  • Intraligamentary
  • Intrapulpal
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6
Q

Two types of local anaesthetics

A
  • Esters
  • Amines(mostly used)
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7
Q

Differences between esters and amines

A
  • In metabolism and allergy production
  • Esters metabolised in plasma
  • Amines primarily undergo hepatic metabolism (prilocaine breakdown also in lungs, articaine metabolism in plasma)
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8
Q

Lidocaine

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

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

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9
Q

Mepivicaine

A

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

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

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10
Q

Prilocaine

A
  • 4% plain solution
  • 3% solution w/ vasocontrictor felypressin(if epinephrine free required)
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11
Q

Formulations of topical anesthetics

A
  • Creams
  • Ointments
  • Sprays
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12
Q

Local anaesthetics agents commonly used as topical

A
  • Lidocaine and Benzocaine
  • Oraqix-Lidocaine and prilocaine
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13
Q

Technique for infiltration anaesthesia

A
  • Mouth partly open
  • Needle to depth of buccal sulcus(if bone contacted-slight withdrawal)
  • Injection site supraperiosteal
  • Aspiration and injection of 1-2 ml
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14
Q

Benefits of slow injection

A
  • Reduces discomfort
  • Increases success
  • Lessens systemic problems
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15
Q

How long do infiltration injections last?

A

Pulps 45 mins and soft tissues 1.5-2 hours

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16
Q

Anaesthetic used in those allergic to amides

A

Procaine

17
Q

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

A

Articaine

18
Q

Articaine

A

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

-Better mandibular infiltration anaesthesia than lidocaine

19
Q

Bupivacaine

A
  • long lasting
  • 1:200 000
  • Supplementary intraoral injection during general anaesthesia
  • Reduces number of post-op analgesics required
20
Q

Effect of Epinephrine in La

A

🔹Vasoconstriction
🔹Reduced bleeding
🔹Prolonged anaesthesia

21
Q

Effects of Epinephrine injection into vessel

A

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

22
Q

Epinephrine effect on heart

A

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

23
Q

Role of epinephrine in allergic reactions

A

🔸Inhibits release of inflammatory mediators
🔸Histamine, leukotrienes

24
Q

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

A

🔸Induces vasoconstriction and reduces vascular permeability

25
Q

Importance of bronchodilation during severe allergic reactions

A

🔸Improved airflow

26
Q

Effects epinephrine has on cardiovascular system during allergic reactions

A

🔸Maintains blood pressure and cardiac output

27
Q

How Articaine has better penetration into tissues than lidocaine

A

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

28
Q

Advantages of Articaines improved penetration

A

🔸More profound anaesthesia at lower doses

29
Q

Main effects of epinephrine in allergy

A

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

30
Q

Active ingredient of Ubistein

A

Articaine and epinephrine

31
Q

Active ingredient of Scandonest

A

Mepivicaine and epinephrine

32
Q

Active ingredient of xylodren

A

Lidocaine and epinephrine

33
Q

Active ingredient of dentocain

A

Articaine and adrenaline

34
Q

Active ingredient of septonest

A

Adrenaline and Articaine

35
Q

Factors that affect intensity and duration of LA’s

A

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

36
Q

How infection hinders effect of La

A

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

37
Q

Strategies to overcome resistance of LA in infected tissues

A

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

38
Q

Overdose of LAs can cause

A

🔹Severe hypotension (Vasodilation)
🔹Seizures
🔹Respiratory depression