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Pharmacology > Local Anesthetics > Flashcards

Local Anesthetics Flashcards

1
Q

Function of LA

A

Prevent transmission of nerve impulse in region to which its applied without affecting consciousness

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2
Q

Which are the topical LAs

A

Lignocaine
Prilocaine
Tetracaine
Benzocaine
Oxybuprocaine

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3
Q

Which are the injectable LAs

A

Bupivacaine
Levobupivicaine
Lignocaine
Mepivacaine
Ropivacine

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4
Q

MOA of LAs

A

block voltage gated Na channels and reduce infux of Na ions
=prevention of depolarisation of membrane by blocking AP

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5
Q

Steps in LA MOA

A

Unionised LA diffuses across CM
LA becomes ionised due to lower intracellular pH
Ionised LA blocks NA channel=prevent propagation of APs

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6
Q

Effects of infected tissue on LA

A

Infected tissue have decr. pH
therefore, fraction of ionised LA is reduced
=reduced effect
Infected tissue have incr. blood supply
= more LA removed from local area before it can have an effect

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7
Q

How does diameter influence LA

A

Smaller diameter nerve fibre= more blocade as compared to Larger diameter fibres

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8
Q

How does myelination affect LA

A

Myelinated fibres are more susceptible to blockade compared to unmyelinated fibres of same size

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9
Q

Order in Fibers blockade

A
  1. Sympathetic and pain
  2. Temperature
  3. Light touch and Proprioception
  4. Motor
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10
Q

Order in fiber recovery

A
  1. Motor
  2. Light touch and Proprioception
  3. Temperature
  4. Sympathetic and pain
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11
Q

DOA of LA depends on

A

-uptake into general circulation
-addiction of vasoconstrictor (AE/E, Levonodefrine)

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12
Q

Effects of adding vasoconstrictor to LA

A

Localise LA at desired site
Prolonged DOA
Reduced local hemorrhage
Reduce amount of LA absorbed into SC
Decrease toxcity

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13
Q

DI of Vasoconstrictor

A

TCAs: potentiate HT effect
Non-selective B-Blockers: incr. BP, reflex decr. HR, monitor BP
Cocaine, Methamphetamine abusers:
incr. risk HT crisis, stroke, MI
Digoxin: narrow TI=cardiac arrythmias

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14
Q

CI of Vasoconstrictors

A

Severe Heart disease
Uncontrolled Hyperthyroidism
Sulphite allergies
Asthmatics (corticosterioid-dependent)
Pheochromocytoma

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15
Q

Topical anaesthesia provide

A

Short term relief
High LA conc. in an oily vehicle slowly penetrate skin or mucous membrane

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16
Q

Infiltration anaesthesia provide

A

numbness faster than topical anesthesia.
LA is injected transdermally/subcutaneously by the area to be anaesthetised

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17
Q

Peripheral nerve block anesthesia provide

A

provide fields of anaesthesia distal to site of injection
Injection of LA around a nerve trunk

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18
Q

Which are the nerve block LAs

A

Bupivacaine
Lignocaine
Ropivacine
Mepivacaine

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19
Q

Central nerve block anaesthesia provide

A

produce anaesthesia above and below site of injection
LA is injected near the spinal cord

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20
Q

E.g of Central nerve block anaesthesia

A

Epidural anesthesia

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21
Q

Which are the Central nerve block LA

A

Bupivacaine
Lignocaine
Ropivacaine

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22
Q

IV regional anaesthesia allow for

A

Manipulation of fractures and minor surgical procedures
LA is injected into a limb after application of tourniquet

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23
Q

Which are the IV regional LA

A

Lignocaine

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24
Q

Which LAs are esters

A

Benzocaine
Oxybuprocaine
Tetracain

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25
Q

Which LAs are amides

A

All have 2 ‘i’s in them
Bupivacaine
Lignocaine
Ropivacaine
Mepivacaine
Prilocaine
Articaine

26
Q

Metabolism of ester LA

A

Via Plasma cholinesterases

27
Q

Metabolism of aminde LAs

A

Cytochrome P450

28
Q

AEs of LAs

A

Psychogenic: alteration in BP, nausea, vomiting. hyperventilation, syncope
Toxcity: CNS, CVS (bupivocaine) and respiratory distress
Allergy: PABA, metabisulfate (with vasoconstrictors)
Parasthesia: more common in Articaine
Methaemoglobinaemia

29
Q

LA toxicity results in

A

SAMS
Slurred speech
Altered CNS
Muscle Twitching
Seizures

30
Q

CNS symptoms in LA toxicity

A

Slurred speech
Tingling of lips
Reduced level of consciousness
Seizures

31
Q

CVS symptoms in LA toxicity

A

Reduced myocardial contractility
Arrythmias
Hypotension: treated with vasodepressors
Ventricular fibrillation caused by Bupivacaine:
treated with Intralipid infusion

32
Q

Indications of Bupivacaine

A

Local infiltration, nerve block, spinal, epidural
Chiefly used for surgical anaesthesia
Useful in providing several days of analgesia

33
Q

Metabolism of Bupivacaine

A

Liver

34
Q

Onset of action of Bupivacaine

A

Slow: 30 mins

35
Q

DOA of Bupivacaine

A

3hrs
Peripheral bloc: 2-24hrs

36
Q

Bupivacaine is mostly used in

A

Labour and postoperatively
Also capable of producing prolonged anesthesia: is potent

37
Q

What is Levobupivacaine

A

is a S-enantiomer of bupivacaine
Has a better CV safety profile than Bupivacaine

38
Q

Indications of Lignocaine

A

Local/tropical
Infiltration
IV regional anaesthesia (biers block)
Epidural anesthesia
Eye blocks

39
Q

Onset of action of Lignocaine

A

Rapid

40
Q

DOA of lignocaine

A

Intermediate

41
Q

CI of lignocaine

A

Heart block/conduction disturbances

42
Q

DI of Lignocaine

A

Cimetidine/beta blockers
NMB

43
Q

Lignocaine is used as

A

Topical spray: larynx
Jelly: urethral anesthesia and haemorrhoids
Patch: (5%,S4) neuropathic pain relief (PHN)

44
Q

DOA of Mepivacaine

A

Intermediate

45
Q

Mepivacaine is used in

A

Dental practice

46
Q

Indications of Mepivacaine

A

Infiltration
Nerve blocks

47
Q

Metabolism of Mepivacaine

A

Liver enzymes

48
Q

DOA of Ropivacaine

A

Long

49
Q

Indications of Ropivacaine

A

Epidural
Local nerve block
Infiltration
Analgesia

50
Q

Metabolism of Ropivacaine

A

Liver enzymes

51
Q

Cautions in Ropivacaine

A

partial or complete heart block
Elderly
Liver dysfunction

52
Q

Articaine is used in

A

Dental and Periodontal procedures

53
Q

Indications of Articaine

A

Infiltration
Nerve blocks

54
Q

What is articaine: an ester or amide

A

Is an amide but contains a an ester side chain which is hydrolysed-plasma esterases

55
Q

T1/2 of articaine

A

20-40mins

56
Q

Onset of action Articaine

A

Rapid: 1-6mins

57
Q

Commonly used formulation of Articaine

A

4% articaine with epinephrine

58
Q

Prilocaine is used as

A

Topical anesthesia
Patch: min app. time of 1hr
Cream:
Mucosa- apply and leave unoccluded for 10-15mins
Intact skin: apply a thick layer and cover with an occlusive dressing for 1-2hrs
(analgesia: apply +- 2hrs after removal of dressing)

59
Q

Tetracaine is used for

A

Topical cream: pain relief in haemorrhoids and minor skin burns
Eye drops: opthalmology in tonometry, foreign body removal, suture removal
Oral gel: pain relief of mucous membranes of mouth, lips and gums

60
Q

Benzocaine is used for

A

Topical gel: dentistry injection site-minimises sensation
Lozenge: surface anaesthetic-pain relief of sore throats
Throat spray
Throat gargle

61
Q

Oxybuprocaine is used for

A

Eye drops: opthalmology in tonometry, foreign body removal, suture removal

62
Q

Oxybuprocaine has

A

an additive bactericidal activity

Pharmacology (50 decks)

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