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Pharmacology of Local Anesthesia

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					       Pharmacology Of Local Anesthesia




PHARMACOLOGY OF LOCAL
     ANESTHESIA
     Dr. Hesham El-Hawary
         Lecturer OMFS
         Cairo Univesity
     www.elhawarydentalclinic.com

                 ELHAWARY
         Pharmacology Of Local Anesthesia




Constituents of the anesthetic
          carpule




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                    Pharmacology Of Local Anesthesia


     Anesthesia with V.C.                   Plain Anesthesia
                                              (without V.C.)
1.   Local anesthetic agent           1. Local anesthetic agent
     ( L.A.)                             ( L.A.)
2.   Vasoconstrictor agent            2. Vehicle to make solution
     ( V.C.)                             isotonic
3.   Preservative for V.C.               ( 0.9%NaCl)
     agent
     (anti- oxidant)
4.   Vehicle to make solution
     isotonic
     ( 0.9%NaCl)


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Pharmacology Of Local Anesthesia




Introduction




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                   Pharmacology Of Local Anesthesia




          Local anesthetic drugs

• Drugs that will temporary interrupt conduction when
  absorbed into the nerve and have little or no irritating
  effect when injected into the tissues



• They are all synthetic compounds except the cocaine



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                     Pharmacology Of Local Anesthesia




Properties of ideal anesthetic agent
1. Reversible action
2. Nonirritant
3. Produce no secondary local reaction (No allergic reaction)
4. No systemic toxicity
5. Rapid onset
6. Sufficient duration
7. Potent
8. Sufficient penetrating properties
9. Stable in solution and undergo biotransformation in body
10. Can be sterilized without deterioration
11. Not interfere with healing of local tissues
12. Have vasoconstrictor action or compatible with V.C.
13. Not expensive
                               ELHAWARY
                          Pharmacology Of Local Anesthesia


    Common properties of injectable LA
               Agents
• Form salts with strong acids which is water soluble
• When injected in the body (alkali)
    – Hydrolyzed by plasma proteins to free the alkaloid base which is lipid
      soluble
    – Undergo biotransformation
•   Affect the nerve conduction and have reversible action
•   Compatible with vasoconstrictors
•   Not or slightly irritant to the tissue in the concentration used
•   Capable of producing toxic effect when sufficient high plasma
    concentration is reached


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         Pharmacology Of Local Anesthesia




Mode of Action Of Local
  Anesthetic Drugs
 Mechanical or Reversible coagulation theory
 Physiological theory
 Acetyl choline and enzyme system theory
 Electrical potential theory
 Displacing calcium ions from receptor sites



                   ELHAWARY
                     Pharmacology Of Local Anesthesia



• The nerve cell membrane is made of proteins and
  phospholipid content and the anesthetic agents are lipid
  soluble

• The proper metabolism leads to normal nerve conduction

• Impulses are conducted along the nerve as an electrical
  waves depends on the difference in the charged ions presents
  inside and outside the nerve

• The transmission at the synaptic junction depends on the
  acetyl choline release and acetyl choline receptors


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                   Pharmacology Of Local Anesthesia


  Mechanical (Reversible) coagulation
                theory
• The free anesthetic base is lipid soluble

• It dissolves in the lipid content of the protoplasm of
  the nerve tissue

• Leading to temporary coagulation

• Transient barrier occluding the conduction of nerve
  impulses
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                    Pharmacology Of Local Anesthesia


              Physiological theory
         (interference with the nerve tissue metabolism)




• The anesthetic drugs interferes with the intracellular
  oxidation of glucose, succinate and ascorbate



• Leading to temporarily affecting the cells and make
  them stop conduction


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                 Pharmacology Of Local Anesthesia


   Acetyl Choline and enzyme system
                 theory


• Local anesthetic drugs affect the acetyl choline
  release and compete for the receptors

• Thus preventing depolarization and inhibit the
  transmission of impulses



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                    Pharmacology Of Local Anesthesia




        Electrical potential theory

• The ionization of local anesthetic drugs produces
  cations

• It affects the negatively charged nervous tissue cells

• Inhibiting their action



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                  Pharmacology Of Local Anesthesia


 Displacing calcium ions from receptor
                  sites


• Anesthetic drug occupies the sites of calcium ions



• It reduces the cell membrane permeability to Na ions



• Preventing depolarization
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      Pharmacology Of Local Anesthesia




Pharmacokinetics of local
      anesthetics
                Uptake
               Potency
               Duration
          Biotransformation
              Excretion



                ELHAWARY
                       Pharmacology Of Local Anesthesia




                              Uptake
•   Most L.A. agents producing vasodilatation
•   Procaine is the most potent vasodilator
•   Cocaine is the only L.A. agents that produces
    vasoconstriction
•   Vasodilatation results in
    –   ↑ rate of absorption
    –   ↓ duration of action of anesthesia
    –   ↑ anesthetic blood level & risk for toxicity



                                 ELHAWARY
                  Pharmacology Of Local Anesthesia




                        Potency
• The majority of local anesthetics are tertiary
  amines
• Few local anesthetics are secondary amines as
  Procaine
• This means that: (an ammonia molecule that has
  3H atoms replaced by an organic radicals)
• NH3 → NR3
• Local anesthetic agent is prepared in the carpule in
  the form of hydrochloride salt of tertiary amine
  ( NR3 ̶ HCL)
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                  Pharmacology Of Local Anesthesia




•   The free base (NR3) of the hydrochloride salt of
    tertiary amine ( NR3 ̶ HCL) is liberated from its
    salt (HCL) by interaction with alkaline medium,
    alkaline PH, ( body fluids, NaHCO3 )

•   (NR3 ̶ HCL) + NaHCO3 → NR3 + Na CL + H2 CO3




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                   Pharmacology Of Local Anesthesia




• In presence of tissue infection or inflammation
  (Acidic PH)
    The free base (NR3) of the hydrochloride salt of tertiary
    amine ( NR3 ̶ HCL) fail to liberated from its salt (HCL)
    & failure of anesthesia occurs


• (NR3 ̶ HCL) + Acidic PH → (NR3 ̶ HCL)




                             ELHAWARY
                           Pharmacology Of Local Anesthesia




                                Duration
The following factors affect both duration & depth of
   anesthetic action :

•       Factors related to the anesthesia
    –     Lipid solubility
    –     Concentration and type of the drug
    –     Ionization constant of the drug (1/œ)
    –     Presence or absence of vaconstrictor or vasoconstriction effect
    –     Duration of exposure




                                     ELHAWARY
                            Pharmacology Of Local Anesthesia




•       Factors related to the injection technique
    –     Technique ( infiltration vs. nerve block)
    –     Volume of the solution
    –     Accuracy of the technique
    –     Anatomical variation


•       Factors related to the site of injection
    –     Alkalinity; Affect the ionization of the drug and the rate of liberation
          of free base
    –     Vascularity of tissue


•       Factors related to the individual to be injected
    –     Individual variation in response



                                      ELHAWARY
                            Pharmacology Of Local Anesthesia


                         Biotransformation
                           (metabolism)

•       Ester group
    –     Metabolized in
         • Plasma by plasma pseudo-cholinesterase enzyme
         • Liver by the estrase enzyme
    –     Toxicity (high toxic blood level) occurs in patients with plasma pseudo-
          cholinesterase enzyme deficiency ( 1 out of 2500)


•       Amide group
    –     Metabolized in
    –     Liver by the liver microsomal enzymes
    –     Toxicity (high toxic blood level) occurs in patients with impaired liver
          function (liver dysfunction)

                                      ELHAWARY
                     Pharmacology Of Local Anesthesia




                         Excretion

•   Both groups of local anesthetics & their metabolites are
    excreted by kidneys

•   Patients with renal dysfunction may be unable to eliminate
    local anesthetics & their metabolites from the blood with
    increase risk of toxicity




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      Pharmacology Of Local Anesthesia




Local Anesthetic Agents




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              Pharmacology Of Local Anesthesia




                   Local anesthetic
                       agents




                                                  Quinoline
Ester Group          Amide Group
                                                 Centbucridine




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                         Pharmacology Of Local Anesthesia




                                Esters
•   Esters of benzoic acid
    –   Cocaine
    –   Butacaine
    –   Tetracaine
    –   Benzocaine
    –   Hexylcaine
•   Esters of Para-aminobenzoic acid
    –   Procaine
    –   Chloroprocaine
    –   Ravocaine
    –   Propoxycaine
•   Esters of Meta - amino benzoic acid
    – Unacaine
    – Primcaine
•   Esters of Para - ethyox benzoic acid
    – Intracaine

                                   ELHAWARY
                  Pharmacology Of Local Anesthesia




                       Amides
•   Lidocaine
•   Bupivacaine
•   Articaine
•   Mepivacaine
•   Prilocaine
•   Etidocaine
•   Ropivacaine



                            ELHAWARY
                   Pharmacology Of Local Anesthesia




    Biotransformation of LA Drugs

• Ester group undergo biotransformation in
  – Liver by the estrase enzyme
  – Plasma by the cholinesterase enzyme




• Amide group undergo biotransformation in the liver



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                 Pharmacology Of Local Anesthesia


Contrast between ester & amide groups

   Features                   Esters                  Amides

 Chemical bond             Ester bond               Amide bond

                           Procaine                   Lidocaine
Common example
                         ( Novocaine)               ( Xylocaine)

    Allergy                     Low                  Very low

                           Plasma
                                                       Liver
 Metabolism in             pseudo-
                                                    microsomal
                        cholinesterase
                                                     enzymes
                           enzyme
                           ELHAWARY
                Pharmacology Of Local Anesthesia



    Keep in mind:
•   Type: ester - amide
•   Onset of action: rapid – slow
•   Duration of action: Long – short
•   Vasodilatation properties: VD – VC- Non
•   Topical anesthetic properties: yes - no
•   Metabolized in: plasma – liver
•   Excreted by: kidney
•   Allergy: allergic – non allergic
•   Available forms: with or without VC


                          ELHAWARY
Pharmacology Of Local Anesthesia




  Lidocaine

      (Xylocaine)




          ELHAWARY
                   Pharmacology Of Local Anesthesia




• The first amide-type local anesthetic

• It has a rapid onset of action (2 minutes versus 6 to
  10 minutes compare to procaine)

• It has longer duration with a more profound effect
  than procaine

• Allergy to amide is rarely to occur



                             ELHAWARY
                 Pharmacology Of Local Anesthesia




• It is metabolized in the liver by the microsomal
  fixed-function oxidases to monoethylglyceine and
  xylidide

• It is well tolerated in the case of plasma
  cholinesterase deficiency

• It is excreted by the kidneys; less than 10%
  unchanged and greater than 80% various
  metabolites

                           ELHAWARY
                      Pharmacology Of Local Anesthesia




• It is available in several forms:
   – Injectable forms
       • 2 % without vasoconstrictor
       • 2% with epinephrine
           – 1:50,000
           – 1:100,000
           – 1:200,000
   – Topical Anesthetic gel: 5%



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       Pharmacology Of Local Anesthesia




       Mepivacaine

Carbocaine, Polocaine, Mepicaine




                 ELHAWARY
                  Pharmacology Of Local Anesthesia




•   Amide type

•   It has a moderate duration of action

•   It has a rapid onset of action (2 min.)

•   It has a mild vasodilatation properties

•   It has a no topical anesthetic properties



                            ELHAWARY
                  Pharmacology Of Local Anesthesia




• It is metabolized in liver by the liver microsomal
  enzymes (hydroxylation & N demethylation)

• It is execrated by kidney ( 1:16 unchanged)

• It is available in several forms:
   – 3% without V.C.
   – 2% with levonordefrine as V.C. (1:20 000) or
      epinephrine (1: 100 000)



                            ELHAWARY
Pharmacology Of Local Anesthesia




   Marcaine

     Bupivacaine




          ELHAWARY
                    Pharmacology Of Local Anesthesia


•   Amide type ( structurally similar to Mepicaine)

•   It is 4 times more potent than Lidocaine

•   It is 4 times less toxic than Lidocaine

•   It is long acting local anesthetics (6 - 9 hours),
    therefore used for lengthy dental procedure &
    management of postoperative pain

•   It has a slow onset of action than Lidocaine (6-10
    min.)

•   It has a no topical anesthetic properties
                              ELHAWARY
                   Pharmacology Of Local Anesthesia




• It is metabolized in liver by liver microsomal
  enzymes



• It is execrated by kidney ( 16% unchanged)



• It is available as 0.5% with epinephrine 1:200 000


                             ELHAWARY
Pharmacology Of Local Anesthesia




   Procaine

      Novocaine




          ELHAWARY
                   Pharmacology Of Local Anesthesia




• Procaine hydrochloride is a short-acting ester type
  local anesthetic

• It was first synthesized in 1905 by Alfred Einhorn,
  and was the first Injectable man-made local
  anesthetic

• It has vasodilating properties

• Procaine has no topical anesthetic action


                             ELHAWARY
            Pharmacology Of Local Anesthesia




It is important in the immediate
management of intra-arterial injection of
other drugs to help break the
arterio-spasm




                      ELHAWARY
                   Pharmacology Of Local Anesthesia




• It is rarely used today
   – It has slow onset of action ( 6-10 min.)
   – It produces allergy

    So it is replaced by more effective and
    hypoallergenic alternative such as lidocaine or
    amide local anesthetic




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                 Pharmacology Of Local Anesthesia




• It is metabolized in the plasma by the enzyme
  pseudo-cholinesterase through hydrolysis into
  Para-amino benzoic acid (PABA) and diethyl
  aminoethanol, which is then excreted by the
  kidneys into the urine

• Allergic reactions to procaine are usually not in
  response to procaine itself, but to PABA



                           ELHAWARY
            Pharmacology Of Local Anesthesia




About 1 in 3000 people have an atypical
form of pseudocholinesterase, which
doesn't hydrolyze ester anesthetics
such as procaine, resulting in a prolonged
period of high levels of the anesthetic in
the blood and increased toxicity




                      ELHAWARY
Pharmacology Of Local Anesthesia




  Prilocaine

         Citanest




          ELHAWARY
                  Pharmacology Of Local Anesthesia


•   Amide type (secondary amine)

•   Articaine was      first       introduced        in   1976   as
    Ultracaine

•   It has a duration of action similar to Xylocaine

•   It has a potency similar to Xylocaine

•   Its onset of action is slightly slower than
    Xylocaine

•   It is a more potent vasodilator than Mepicaine
    but less than Xylocaine
                            ELHAWARY
                  Pharmacology Of Local Anesthesia




•   It is metabolized in liver by the liver microsomal
    enzymes into orthtoluidine & N- propylalanine

•   Orthtoluidine is able to induce formation of
    methemoglobin,          resulting         in
    methaemoglobinaemia

•   Methaemoglobinaemia can be reversed by the
    administration of 2mg/kg body weight of
    1%methylene blue IV over 5 min


                            ELHAWARY
                  Pharmacology Of Local Anesthesia




• It is execrated faster than other amides by kidney


• It has no topical anesthetic properties but
  EMLA topical anesthetic cream (eutectic mixture of
  local anesthetic) composed of Lidocaine /
  Prilocaine mixture

• It is available as 4% with (1:200 000 epinephrine) or
  without V.C.


                            ELHAWARY
Pharmacology Of Local Anesthesia




   Articaine




          ELHAWARY
                  Pharmacology Of Local Anesthesia




•   Amide type

•   It is more potent than Lidocaine (1.5 times)

•   It has a rapid onset of action (2 min)

•   It has a vasodilatation properties similar to
    Lidocaine

•   It has a no topical anesthetic properties

                            ELHAWARY
                  Pharmacology Of Local Anesthesia




• It is metabolized in both plasma & liver by plasma
  carboxyestrase enzymes to articainic acid

• It is execrated by kidney ( 10% unchanged)

• It is available as 4% with ( 100 000 or 1:200 000
  epinephrine) or without V.C



                            ELHAWARY
                  Pharmacology Of Local Anesthesia




•   Methylparaben ( 1mg/ml) is added to local
    anesthetic carpule as preservative to L.A. agent
    as Articaine, but may cause allergic reactions

•   Therefore patients with para -group allergy
    (sulfur & procaine containing drugs) should
    not take local anesthetic carpule that contains this
    preservative

•   Formulations of Articaine without Methylparaben
    are now available


                            ELHAWARY
Pharmacology Of Local Anesthesia




   Buycaine




          ELHAWARY
                   Pharmacology Of Local Anesthesia




•   Ester type

•   It is potent like Lidocaine but less toxic

•   It has a no topical anesthetic properties

•   It is hydrolyzed in plasma by plasma pseudo-
    cholinesterase enzyme

•   It is execrated by kidney

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                 Pharmacology Of Local Anesthesia




• It is available as 3% with:

  – Epinephrine 1:25 000
  – Epinephrine 1:50 000
  – Nor-Epinephrine 1:50 000
  – Nor-Epinephrine 1:20 000




                           ELHAWARY
Pharmacology Of Local Anesthesia




 Tetracaine

      Pontocaine




          ELHAWARY
                   Pharmacology Of Local Anesthesia




•   Ester type

•   It is more potent than procaine ( 10 times)

•   It is more toxic than procaine ( 10 times)

•   It has a no topical anesthetic properties



                             ELHAWARY
                   Pharmacology Of Local Anesthesia




• It is hydrolyzed in plasma by plasma pseudo-
  cholinesterase enzyme

• It is execrated by kidney

• It is available as 0.15% concentration

• It is used either alone or combined with procaine To
  increase the depth & duration of anesthesia

                             ELHAWARY
Pharmacology Of Local Anesthesia




   Unacaine




          ELHAWARY
                   Pharmacology Of Local Anesthesia




•   Ester type

•   It is more potent than procaine (2 times)

•   It is less toxic than procaine

•   It has short duration of action

•   It has a no topical anesthetic properties


                             ELHAWARY
                Pharmacology Of Local Anesthesia




• It is hydrolyzed in plasma by plasma pseudo-
  cholinesterase enzyme

• It is execrated by kidney

• It is available as 3% concentration with or
  without adrenaline


                          ELHAWARY
        Pharmacology Of Local Anesthesia




Maximum doses of L.A. agents




                  ELHAWARY
              Pharmacology Of Local Anesthesia


 L.A. agent            Max. dose                 Normal dose


 Lidocaine                300 mg                 4.4 mg / kg


Mepivacaine               400 mg                 6.6 mg / kg


 Marcaine                  90 mg                 1.3 mg / kg


 Articaine                400 mg                  6 mg / kg


 Prilocaine               500 mg                  7 mg / kg


                        ELHAWARY
     Pharmacology Of Local Anesthesia




Dilution of L.A. agents




               ELHAWARY
                 Pharmacology Of Local Anesthesia


   The dilution of L.A. agent as 2 % means that
   there is two grams (2000 mg) of the L.A.
   agent in 100 ml of the solution


              2000 mg                      100 mL

               X mg                         1.8 mL

             X = 1.8 X 2000 / 100 = 36 mg


Therefore carpule of 1.8 ml contains 36 mg solution
                           ELHAWARY
         Pharmacology Of Local Anesthesia




Constituents of the anesthetic
          carpule




                   ELHAWARY
                    Pharmacology Of Local Anesthesia


     Anesthesia with V.C.                   Plain Anesthesia
                                              (without V.C.)
1.   Local anesthetic agent           1. Local anesthetic agent
     ( L.A.)                             ( L.A.)
2.   Vasoconstrictor agent            2. Vehicle to make solution
     ( V.C.)                             isotonic
3.   Preservative for V.C.               ( 0.9%NaCl)
     agent
     (anti- oxidant)
4.   Vehicle to make solution
     isotonic
     ( 0.9%NaCl)


                              ELHAWARY
                    Pharmacology Of Local Anesthesia




    Keep in mind:

•    The main agent in the local anesthetic carpule is
     the L.A. agent

•    The other ingredients of the local anesthetic
     carpule are added :

    1. To potentiate the action of the L.A. agent
    2. To prevent deterioration of the contents of the local
       anesthetic carpule

                              ELHAWARY
    Pharmacology Of Local Anesthesia




The Vasoconstrictor




              ELHAWARY
                          Pharmacology Of Local Anesthesia




                          Advantages
                     It causes V.C. of B.V. that
1.    Aid in producing local ischemia by vasocntricting the
      blood vessels leading to:
     1.   Aids positively in producing anesthesia
     2.   Decreases bleeding caused by the surgical procedure
2.    Decreases absorption rate of the anesthetic drug
      leading to:
     1.   Increases duration of action of the L.A.
     2.   Decreases the volume of local anesthetic solution needed
     3.   Decreases the toxicity of the anesthetic drug
3.    It stimulate the heart
          Thus counteract the depressant effect of the local anesthetic agent
          on the heart


                                    ELHAWARY
                        Pharmacology Of Local Anesthesia




                  Contra-Indications
1.   Diabetics:
       As V.C. counteract the action of insulin
       i.e. ( increase blood glucose level)


2.   Hypertensive pt:
       As V.C. raises patient’s blood pressure


3.   Cardiac pt.:
       As V.C. stimulate the heart, produce tachycardia & increase H.R.
       ( this is doubtful because of the small amount used which is about
       0.04 mg if 2 ml of 1:50 000 solution is used & this is about 1/5
       permissible dose that can be given to cardiac pt without ill effect)

                                  ELHAWARY
                        Pharmacology Of Local Anesthesia




              Contra-Indications Cont.
4.   Pregnancy:
     Because the V.C. causes uterine contraction & may causes abortion


5.   Extraction of teeth with chronic peri-apical sepsis:
     Because V.C. decrease blood flow to the tissues & may lead to dry
     socket


5.   Hyperthyroidism (toxic goiter):
     Because V.C. specially adrenaline may cause thyroid crisis & sudden
     death


                                  ELHAWARY
                 Pharmacology Of Local Anesthesia




                Types of V.C.
1. Epinephrine ( adrenaline)

2. Nor- Epinephrine ( nor - adrenaline)

3. Neo- cobefrin (levonordefrin)

4. Phenylephrine (neosynephrine)

5. Felypressin (octapressin)

                           ELHAWARY
          Pharmacology Of Local Anesthesia




     Dilution of V.C. Cont.

The dilution of V.C. 1: 1000
means that there is one gram
(1000 mg) of the V.C. in 1000 ml
( 1 liter) of the solution, or in other
words 1.0 mg/ml of the solution




                    ELHAWARY
                  Pharmacology Of Local Anesthesia




• Examples
1: 50 000 means 0.02mg/ml
      1 gm : 50 000 ml
      1000 mg : 50 000 ml
      (1000/50 000) mg : (50 000/50 000) ml
      (1/50) mg : (1/1) ml
      0.02 mg: 1 ml or 0.02mg/ml



                            ELHAWARY
                  Pharmacology Of Local Anesthesia




• Examples
1: 20 000 means 0.05mg/ml
      1 gm : 20 000 ml
      1000 mg : 20 000 ml
      (1000/20 000) mg : (20 000/20 000) ml
      (1/20) mg : (1/1) ml
      0.05 mg: 1 ml or 0.05mg/ml



                            ELHAWARY
                    Pharmacology Of Local Anesthesia



              Epinephrine ( adrenaline)

•   Most commonly used V.C. in the dental carpule

•   Chemically unstable , it undergoes deterioration through
    oxidation

•   Preservative such as sodium bisulfite is added to prevent
    oxidation of adrenaline

•   It acts on both         α      &     β      adrenergic   receptors
    (β predominates)



                              ELHAWARY
               Pharmacology Of Local Anesthesia




            Systemic effects
 CVS: epinephrine acts on β1 receptors so it:
    Increases cardiac output
    Increases the heart rate
 CVS: epinephrine acts on α receptors so it:
    Produces dilatation of coronaries
    Produces peripheral vasoconstriction
 RS: epinephrine acts on β2 receptors causing
  broncho-dilatation
 CNS: epinephrine produce mild stimulation
                         ELHAWARY
           Pharmacology Of Local Anesthesia




N.B. Action of epinephrine is finished
by reuptake of         epinephrine by
adrenergic nerves or inactivation by
MAO & COMT
 ( Catechol - O- Methyl Transferase)




                     ELHAWARY
                 Pharmacology Of Local Anesthesia




                  Availability
Available in various combination with L.A. agent as:

  1. 1: 50 000

  2. 1: 80 000

  3. 1: 100 000

  4. 1: 200 000
                           ELHAWARY
                      Pharmacology Of Local Anesthesia


          Nor- Epinephrine ( nor - adrenaline)

•   It acts on both           α      &     β      adrenergic   receptors
    (α predominates)

•   It is 1/4 as potent as epinephrine

•   It is 1/8 epinephrine in raising blood sugar level

•   It has shorter duration than epinephrine

•   It is less toxic than epinephrine

•   Concentration used is 1: 30 000

                                ELHAWARY
                    Pharmacology Of Local Anesthesia




               Systemic effects
 CVS:
   Increases both B.P. & peripheral vasoconstriction
   Decreases both H.R. & cardiac output


 RS: nor-epinephrine has mild bronchodilatation effect

 CNS: nor-epinephrine produce mild stimulation



                              ELHAWARY
                    Pharmacology Of Local Anesthesia



              Levonordefrin (neo - cobefrin)
•   It acts on both α (75%) & β (25%) adrenergic
    receptors

•   It is similar pharmacologically to epinephrine

•   It   is    only 15% as               potent        as   epinephrine
    ( less effective in contracting B.V. & in raising B.P. than
    epinephrine & only 1/10 as active as epinephrine in
    raising blood sugar level)


•   Concentration used is 1: 20 000
                              ELHAWARY
                  Pharmacology Of Local Anesthesia



                   Phenylephrine

•   The most stable V.C. agent

•   The weakest V.C. agent

•   It is 5% potent as epinephrine

•   It has a direct α receptor stimulation ( 95%)

•   Concentration used is 1: 2 500 with 4% procaine
                            ELHAWARY
                     Pharmacology Of Local Anesthesia



             Felypressin (Octapressin)
•   It is a synthetic analogue to anti-diuretic hormone
    vasopressin
•   The incidence of systemic reactions to felypressin is
    minimal
•   It has no effect on the myocardium, thus it is safe for
    cardiac pt
•   It has no effect on adrenergic nerve transmission , thus it
    is safe for pt. with hyperthyroidism
•   It has anti-diuretic & oxytoxic actions , thus
    contraindicated in pregnancy
•   Concentration used is 0.03 IU/ml with prilocaine


                               ELHAWARY
                  Pharmacology Of Local Anesthesia




    Maximum Doses Of V.C.
     V.C.                   Max. dose                Concentration

 epinephrine              0.2mg         20ml          1 : 100 000

nor epinephrine          0.34mg          10ml         1 : 100 000

 levonordefrin            1.0mg         20ml          1 : 20 000

Phenylephrine             4.0mg         20ml           1 : 2 500

  felypressin             0.27 IU         9ml           0.03 IU

                            ELHAWARY
Pharmacology Of Local Anesthesia




      Vehicle




          ELHAWARY
                   Pharmacology Of Local Anesthesia




•   The vehicle to make the local anesthetic solution
    isotonic

•   The isotonicity of the local anesthetic solution is
    important to produce the desired anesthetic
    effect

•   It may be:
    –   Saline solution ( 0.9 % Na CL)
    –   Ringer’s solution (0.5 % Na CL , 0.04 % Ca CL and
        0.02 % K CL)

                             ELHAWARY
                            Pharmacology Of Local Anesthesia

•                                                 hypotonic:
         If the injected anesthetic solution is hypotonic
         water will pass from the injected anesthetic
         solution to inside the tissue cells until equilibrium
         occurs between the intercellular & the
         intracellular fluids & this results in:

1.       Postoperative pain & delayed healing:
         As water escapes from the injected                    solution
         intercellularly:
     •     Increases the volume of intercellular fluid
     •     Rupture of the cells in the area occurs

2.       Less profound anesthesia:
           As viscosity of the injected solution increased due to
           loss of water & thus the power of diffusion of the
           injected solution in the area is reduced

                                      ELHAWARY
                      Pharmacology Of Local Anesthesia


•                                              hypertonic:
     If the injected anesthetic solution is hypertonic
     water will escape from the intracellular fluids to
     outside towards the injected anesthetic solution
     until equilibrium occurs between the intercellular
     & the intracellular fluids & this results in:

1.   Postoperative pain & delayed healing:
     As water escapes from the cells, the volume of
     intercellular fluid decreases & shrinkage of the cells in the
     area occurs
2.   Less profound anesthesia:
     As concentration of the injected solution decreased due
     gain of water ( dilution of the injected solution in the area)

                                ELHAWARY
Pharmacology Of Local Anesthesia




Preservative




          ELHAWARY
                      Pharmacology Of Local Anesthesia




•   Na bisulphite (0.5mg/ml)
    –   It is added to local anesthetic carpule to prevent
        oxidation of the V.C. agent


•   Methylparaben ( 1mg/ml)
    –   It is added to local anesthetic carpule as preservative to
        L.A. agent as Articaine
    –   It may cause allergic reactions
    –   Patients with para -group allergy (sulfa & procaine)
        should not take local anesthetic carpule that contains
        this preservative


                                ELHAWARY
   Pharmacology Of Local Anesthesia




Topical anesthetics




             ELHAWARY
                  Pharmacology Of Local Anesthesia




1. Topical anesthetics that produce their effect by the
    chemical action on the free nerve endings
    ( spray, gel, or ointment):
   – Xylocaine (5-10%)
   – Benzocaine (10-20%)

2. Topical anesthetics that produce their effect by the
   means of the refrigerant action:
  –   Application of cold on the surface             of   mucous
      membranes ( ice bags or crushed ice)
  –   Topical use of ethyl chloride


                            ELHAWARY
       Pharmacology Of Local Anesthesia




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www.elhawarydentalclinic.com



                 ELHAWARY

				
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