local anesthetics

1. Local AnesthesiaLocal Anesthesia

2. Local AnesthesiaLocal Anesthesia
 DefinitionsDefinitions
 Chemical structureChemical structure
 ClassificationClassification
 Mechanism of actionMechanism of action
 Routes of administrationRoutes of administration
 PharmacokineticsPharmacokinetics
 Prolongation of actionProlongation of action
 ComplicationsComplications
 ToxicityToxicity
 Ideal local anestheticsIdeal local anesthetics

3. What are local anesthetics ?What are local anesthetics ?
 Local anesthetic results in loss ofLocal anesthetic results in loss of
sensation without loss of consciousnesssensation without loss of consciousness
through blocking of sensory and nervethrough blocking of sensory and nerve
conduction .conduction .

4. AnalgesicsAnalgesics
 Drugs used to relieve pain without loss ofDrugs used to relieve pain without loss of
consciousness “ Generally “consciousness “ Generally “

5. Mechanism Of ActionMechanism Of Action
 Local anesthetic drugs act by preventing the generation and conductionLocal anesthetic drugs act by preventing the generation and conduction
of nerve impulses by blocking NA channelsof nerve impulses by blocking NA channels
 Na channels consist of two gates m , h gatesNa channels consist of two gates m , h gates
 At resting potential , the m gate is closed and the h gate is opened .At resting potential , the m gate is closed and the h gate is opened .
 With effective action potential , the m gate is opened allowing rapid influxWith effective action potential , the m gate is opened allowing rapid influx
of Na ionsof Na ions
 Few seconds later , the H gate closesFew seconds later , the H gate closes
 L A are weak bases available as saltsL A are weak bases available as salts
RnH (Rn) + (H+)RnH (Rn) + (H+)
Water soluble lipid solubleWater soluble lipid soluble

12. Chemical structureChemical structure

13. ClassificationClassification
 EsterEster
 CocaineCocaine
 Procaine (Novocaine)Procaine (Novocaine)
 Tetracaine (Pontocaine)Tetracaine (Pontocaine)
 BenzocaineBenzocaine
 AmideAmide
 Lidocaine (Xylocaine)Lidocaine (Xylocaine)
 Bupivocaine (Marcaine)Bupivocaine (Marcaine)
 Prilocaine (Citanest)Prilocaine (Citanest)
 ArticaineArticaine

14. Structures of Amides and EstersStructures of Amides and Esters
 The amine end is hydrophilic (soluble in water), anesthetic moleculeThe amine end is hydrophilic (soluble in water), anesthetic molecule
dissolve in water in which it is delivered from the dentist’s syringe into thedissolve in water in which it is delivered from the dentist’s syringe into the
patient’s tissue. It’s also responsible for the solution to remain on eitherpatient’s tissue. It’s also responsible for the solution to remain on either
side of the nerve membrane.side of the nerve membrane.
 The aromatic end is lipophilic (soluble in lipids). Because nerve cell is madeThe aromatic end is lipophilic (soluble in lipids). Because nerve cell is made
of lipid bilayer it is possible for anesthetic molecule to penetrate through theof lipid bilayer it is possible for anesthetic molecule to penetrate through the
nerve membrane.nerve membrane.
 The trick the anesthetic molecule must play is getting from one side of theThe trick the anesthetic molecule must play is getting from one side of the
membrane to the other.membrane to the other.

15. Differences of Esters and AmidesDifferences of Esters and Amides
 Two classes of local anesthetics are amino amides and amino esters.Two classes of local anesthetics are amino amides and amino esters.
 Amides:Amides: Esters:Esters:
--Amide link b/t intermediate--Amide link b/t intermediate --Ester link b/t intermediate chain an chain--Ester link b/t intermediate chain an chain
and aromatic ringand aromatic ring aromatic ringaromatic ring
--Metabolized in liver and very--Metabolized in liver and very --Metabolized in plasma through--Metabolized in plasma through
stable in the solutionstable in the solution pseudocholinesterases and notpseudocholinesterases and not
stable in the solutionstable in the solution
--Rarely or doesn’t cause allergey --Cause allergic reaction--Rarely or doesn’t cause allergey --Cause allergic reaction

16. Factors Affect the Reaction of Local AnestheticsFactors Affect the Reaction of Local Anesthetics
Lipid solubilityLipid solubility
 All local anesthetics have weak bases. Increasing the lipid solubilityAll local anesthetics have weak bases. Increasing the lipid solubility
leads to faster nerve penetration, block sodium channels, and speedleads to faster nerve penetration, block sodium channels, and speed
up the onset of action.up the onset of action.
 The more tightly local anesthetics bind to the protein, the longer theThe more tightly local anesthetics bind to the protein, the longer the
duration of onset action.duration of onset action.
 Local anesthetics have two forms, ionized and nonionized.Local anesthetics have two forms, ionized and nonionized.
 The non-ionized form can cross the nerve membranes and block theThe non-ionized form can cross the nerve membranes and block the
sodium channels.sodium channels.
 So, the more non-ionized presented, the faster the onset action.So, the more non-ionized presented, the faster the onset action.
pH influencepH influence
 Usually at range 7.6 – 8.9Usually at range 7.6 – 8.9
 Decrease in pH shifts equilibrium toward the ionized form, delayingDecrease in pH shifts equilibrium toward the ionized form, delaying
the onset action.the onset action.
 Lower pH, solution more acidic, gives slower onset of actionLower pH, solution more acidic, gives slower onset of action

17. Factors Affect the Reaction of Local AnestheticsFactors Affect the Reaction of Local Anesthetics
(cont.)(cont.)
VasodilationVasodilation
 Vasoconstrictor is a substance used to keep the anesthetic solution inVasoconstrictor is a substance used to keep the anesthetic solution in
place at a longer period and prolongs the action of the drugplace at a longer period and prolongs the action of the drug
 vasoconstrictor delays the absorption which slows down thevasoconstrictor delays the absorption which slows down the
absorption into the bloodstreamabsorption into the bloodstream
 Lower vasodilator activity of a local anesthetic leads to a slowerLower vasodilator activity of a local anesthetic leads to a slower
absorption and longer duration of actionabsorption and longer duration of action
 Vasoconstrictor used the naturally hormone called epinephrineVasoconstrictor used the naturally hormone called epinephrine
(adrenaline). Epinephrine decreases vasodilator.(adrenaline). Epinephrine decreases vasodilator.
Side effects of epinephrineSide effects of epinephrine
 Epinephrine circulates the heart, causes the heart beat stronger andEpinephrine circulates the heart, causes the heart beat stronger and
faster, and makes people feel nervous.faster, and makes people feel nervous.

18.  Vascularity of the tissuesVascularity of the tissues
more vasculraized low duration ofmore vasculraized low duration of
action .action .
 Inc.Inc. volume & concvolume & conc inc. durationinc. duration
of actionof action

19. pharmacokineticspharmacokinetics

20.  LA are weak bases so it must dissociate inLA are weak bases so it must dissociate in
tissues to liberate from the basetissues to liberate from the base
 This dissociation is delayed in apnormalThis dissociation is delayed in apnormal
acidic mediumacidic medium
 Therefore LA are not effective in inflamedTherefore LA are not effective in inflamed
tissue as they tend to be more acidic thantissue as they tend to be more acidic than
normal .normal .

21. AbsorptionAbsorption

22.  From mucus membranesFrom mucus membranes
 well absorped LAwell absorped LA
-- CoacineCoacine
- prilocaine- prilocaine
- lidocaine- lidocaine
They can be used in surface anesthesiaThey can be used in surface anesthesia
 Not well absorped :Not well absorped :
-- procaineprocaine

23. MetabolismMetabolism

24.  EsterEster compounds are hydrolysed bycompounds are hydrolysed by
plasma&liverplasma&liver pseudocholinestrase .pseudocholinestrase .
 AmideAmide group are dealkaylated in the livergroup are dealkaylated in the liver
and then hydrolysed by the microsomaland then hydrolysed by the microsomal
enzymesenzymes

25. EliminationElimination
Metabolites mostly eliminated by the kidneyMetabolites mostly eliminated by the kidney

26. Prolongation of actionProlongation of action

27.  Delay absorption :Delay absorption :
- reduce systemic effects- reduce systemic effects
- prolong their duration of action- prolong their duration of action
 AdrenalineAdrenaline : compound with LA induce VC to delay: compound with LA induce VC to delay
their absorption .their absorption .
 Chloroprocaine : the most widely usedChloroprocaine : the most widely used
 Felypressin (alternative VC ) :Felypressin (alternative VC ) :
synthetic vasopressin in which conc. does not affect BPsynthetic vasopressin in which conc. does not affect BP
Or the heart so it can be used in cardiac patient .Or the heart so it can be used in cardiac patient .

28. Routes of administrationsRoutes of administrations
 Surface anesthesiaSurface anesthesia
 InfiltrationInfiltration
 Nerve blockNerve block
 Spinal anesthesiaSpinal anesthesia
 Epidural anesthesiaEpidural anesthesia
 IntravenousIntravenous
 Peripheral nervesPeripheral nerves

29. Surface anesthesiaSurface anesthesia
 Used in the form of creamy , spray , orUsed in the form of creamy , spray , or
ointmentointment
 Used in case of Nose,Mouth,Eye or airUsed in case of Nose,Mouth,Eye or air
passage anesthesiapassage anesthesia

32. InfiltrationInfiltration
 AnestheticAnesthetic drugs are injecteddrugs are injected into or aroundinto or around
the affecting area to be anesthetized .the affecting area to be anesthetized .
 Eg : CyctectomyEg : Cyctectomy
 It’s usually given with vasoconstrictorIt’s usually given with vasoconstrictor
( adrenaline ) to( adrenaline ) to
- delay its absorption- delay its absorption
- prolong duration of action- prolong duration of action
 ExceptExcept in extremitiesin extremities to avoidto avoid GANGRENEGANGRENE

33. Local anesthetics - vasoconstrictorsLocal anesthetics - vasoconstrictors
Vasoconstrictors should not be used in theVasoconstrictors should not be used in the
following locationsfollowing locations
 FingersFingers
 ToesToes
 NoseNose
 Ear lobesEar lobes

34. Nerve BlockNerve Block
 Usually given near nerve plexus or trunkUsually given near nerve plexus or trunk
and done by injection .and done by injection .
 Eg :Eg : Anesthesia of the branchial plexusAnesthesia of the branchial plexus
 Uses :Uses :
surgical anesthesia or post-operativesurgical anesthesia or post-operative
analgesia in the distribution of the plexus .analgesia in the distribution of the plexus .

37. Spinal anesthesiaSpinal anesthesia
 AnestheticsAnesthetics are injected into theare injected into the
subarachnoid space ,subarachnoid space , usually L3 & L4usually L3 & L4 ,,
affecting the spinal cord .affecting the spinal cord .
 Used in surgeries ofUsed in surgeries of abdomen pelvisabdomen pelvis
andand lower limbslower limbs

40. Epidural AnesthesiaEpidural Anesthesia
 Injected in the epidural space at any levelInjected in the epidural space at any level
of the spinal column .of the spinal column .
 Uses :Uses :
Anesthesia/analgesia of the thorax, abdomen,Anesthesia/analgesia of the thorax, abdomen,
lower extremities .lower extremities .

46. IntravenousIntravenous
 AA pressure cuffpressure cuff is used to arrest the blood flow ,is used to arrest the blood flow ,
then local anesthetic is injected into a vienthen local anesthetic is injected into a vien distal todistal to thethe
pressure cuffpressure cuff
it’sit’s not safenot safe andand systemic toxicitysystemic toxicity is a seriousis a serious
hazardhazard
 Uses :Uses :
any surgical procedure on an extremityany surgical procedure on an extremity

48. PeripheralPeripheral nerve blocknerve block
 Injecting local anesthetic near theInjecting local anesthetic near the
course of a named nervecourse of a named nerve
 Uses:Uses:
Surgical procedures in the distribution of theSurgical procedures in the distribution of the
blocked nerveblocked nerve

51. Adverse EffectsAdverse Effects
side effectsside effects

52. Miss judging the anatomy of LAMiss judging the anatomy of LA
Local side effects :Local side effects :
 lymph traumalymph trauma
Vascular injuryVascular injury
Intraglandular injectionIntraglandular injection

53. Complications of localComplications of local
anesthesiaanesthesia

54.  These are systemic manifestations , which occur with large doses, affectingThese are systemic manifestations , which occur with large doses, affecting
different systems and organs .different systems and organs .
 CNS :CNS :
a-Excitation (stimulation of the cerebral cortex )a-Excitation (stimulation of the cerebral cortex )
b- it may affect some centers :b- it may affect some centers :
Respiratory center : depressionRespiratory center : depression
Visual centers : visual disturbancesVisual centers : visual disturbances
c- patients may enter into comma and die .c- patients may enter into comma and die .
 CVS :CVS :
usually occur with spinal anesthesiausually occur with spinal anesthesia
a- myocardial depression : bradycardiaa- myocardial depression : bradycardia
b- Hypotension ( sympathetic block )b- Hypotension ( sympathetic block )
c- it may lead to severe cardiovascular collapse and death .c- it may lead to severe cardiovascular collapse and death .

55.  AllergyAllergy
-May range from itching and skin rashes to as severe as-May range from itching and skin rashes to as severe as
anaphylaxis .anaphylaxis .
- Esters are metabolized into paraaminobenzoic acid (paba ) , is- Esters are metabolized into paraaminobenzoic acid (paba ) , is
responsible .responsible .
- Amides are rare .- Amides are rare .

56. Post operativePost operative

57.  Parasethesia :Parasethesia :
Loss of sensationLoss of sensation
 Hyperthesia :Hyperthesia :
Over response to stimuliOver response to stimuli
 Dysthesia :Dysthesia :
Pain following ordinary stimuliPain following ordinary stimuli

58. Local Anesthetics - ToxicityLocal Anesthetics - Toxicity
Tissue toxicity - RareTissue toxicity - Rare
 Can occur ifCan occur if
administered in highadministered in high
enough concentrationsenough concentrations
(greater than those used(greater than those used
clinically)clinically)
 Usually related toUsually related to
preservatives added topreservatives added to
solutionsolution
Systemic toxicity - RareSystemic toxicity - Rare
 Range fromRange from
lightheadedness, tinnituslightheadedness, tinnitus
to seizures andto seizures and
CNS/cardiovascularCNS/cardiovascular
collapsecollapse

59. Ideal LAIdeal LA
 Low systemic toxicityLow systemic toxicity
 Onset of action should be greatOnset of action should be great
 Not irritant to the site of administrationNot irritant to the site of administration
 Reversible effectReversible effect
 Soluble in water , stable in solutionsSoluble in water , stable in solutions
 Not dissociated by the heatNot dissociated by the heat

61.  Aromatic ring of LA is responsible of ………….Aromatic ring of LA is responsible of ………….
 The more non-ionized presented , the….The more non-ionized presented , the….
……… the onset of action .……… the onset of action .
 Increase vascularity cause ………duration ofIncrease vascularity cause ………duration of
action .action .
 Amides are contraindicated in …………………Amides are contraindicated in …………………
 Esters are metabolized into ………….. WhichEsters are metabolized into ………….. Which
is responsible of allergic reactionis responsible of allergic reaction

63. Presented byPresented by
Zakaria khalil mansour 5212126Zakaria khalil mansour 5212126