This document provides information on local anesthesia. It begins by defining local anesthesia and classifying local anesthetics. It then discusses the pharmacokinetics and mechanisms of action of local anesthetics. Factors that affect the efficacy of local anesthetics like pH, inflammation, dosage, and vasoconstrictors are covered. Potential adverse effects and allergic reactions are described. Guidelines for administering local anesthesia to special patient populations like children, handicapped patients, and those on anticoagulants are provided. The document concludes by discussing dosing considerations and choices of local anesthetic for different procedures.

1. Iyad M.Abou Rabii
Qassim University – College of
Local Anesthetia Dentistry
3rd year - January 2010

2. Lecture Objective
– Define local anesthesia.
– Classify local anesthetics into the two major categories according to their chemical
structure.
– Confer the pharmacokinetics of local anesthetics.
– Describe the anatomical variations and pulpal conditions as complicating factors for local
anesthetics.
– Understand the clinical options of different delivery methods of local anesthetics.
– Explain factors Affect the Reaction of Local Anesthetics
– List undesired systemic effects of local anaesthetics and vasoconstrictors
– Describe local anesthesia allergic (anaphylactic) shock etiology and management
– Description of special medical cases in local anesthesia (child, pregnant woman ,
geriatric, handicapped patient)
– List Local anesthetics interaction with other drugs.
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3. Local anaesthetics
 Definition and function
Local anesthetics (LA) are drugs that are used to prevent or relieve
pain in specific regions of the body without loss of consciousness. They
act by reversibly blocking nerve conduction.
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4. Cell Membrane Receptors
Page  4

5. Membrane potential and neurotransmission:
 Neuron transmits information mainly by two mechanisms:
– chemical
– and electrical signals.
 Information within a neuron is mainly transmitted by electrical signals.
 Electrical signals are propagated by the mechanism called action
potential.
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6. Mechanism
Page  6

7. Mechanism
Page  7

8. Mechanism
Page  8

9. How Local Anesthetics Work
Altering the basic potential of the nerve
membrane
Altering the threshold or firing level
Decrasing the rate of depolarization
Prolonging the rate of repolarization
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10. LOCAL ANESTHETICS CALSIFICATION
– Esters Cocaine, Procaine Chlore procaine
,Tetracaine .
– Amids : Lidocaine Mepivacaine, Prilocaine Articaine
Popivacaine, Etidocaine.
– Ketons :Dyclon.
– Quinoline: Centbucridine .
Page  10

11. Differences of Esters and Amides
 Two classes of local anesthetics are amino amides and amino esters.
Amides: Esters:
--Amide link b/t intermediate --Ester link b/t intermediate chain and chain
and aromatic ring aromatic ring
--Metabolized in liver and very --Metabolized in plasma
--Cause allergic reactions
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12. Pharmacokinetics
 Following injection into the area of nerve fibers to be blocked, local
anesthetics are absorbed into blood.
– Ester-linked local anesthetics are quickly hydrolyzed by butyrylcholinesterase in
blood.
– Amide-linked local anesthetics can be widely distributed via circulation. Amide-
linked local anesthetics are hydrolyzed by liver microsomal enzymes. Thus,
half lifes of these drugs are significantly longer and toxicity is more likely to
occur in patients with impaired liver function.
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13. Pharmacokinetics
 Absorption of local anesthetics is affected by following factors:
– dosage,
– site of injection,
– drug-tissue-binding and
– Presence of vaso-constricting drugs
Page  13

14. Vasoconstrictors
Page  14

15. Application of local anaesthesia
1-- Topical Anesthesia
Anesthesia of mucous membranes of the nose, mouth and throat can be
produced by direct application of aqueous solutions of salts of many
local anesthetics or by suspension of the poorly soluble local anesthetics
as tetracaine (2%) or lidocaine (2%).
Epinephrine, topically applied, has no significant local effect and does
not prolong the duration of action of local anesthetics applied to mucous
membranes because of poor penetration.
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16. Application of local anaesthesia
2-- Infiltration Anesthesia
Infiltration anesthesia is the injection of local anesthetic directly into
tissue without taking into consideration the course of nerves.
 The local anesthetics used most frequently for infiltration anesthesia are
1- lidocaine
2- procaine
3- bupivacaine
When used without epinephrine, greater amounts could be given.
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17. Application of local anaesthesia
3- Field Block Anesthesia
Field block anesthesia is produced by subcutaneous injection of a
solution of local anesthetic in order to anesthetize the region distal to the
injection.
4- Nerve block:
Injection of a solution of a local anesthetic into or about individual
peripheral nerves or nerve plexuses
Page  17

18. Factors Affect the Reaction of Local
Anesthetics
pH influence
 Usually at range 7.6 – 8.9
 Decrease in pH shifts equilibrium toward the ionized form, delaying the
onset action.
 Lower pH, solution more acidic, gives slower onset of action
Page  18

19. Effect of inflammation on the
activity of local anaesthetics
 Inflammation increases the acidity of the medium
 Therefore, administration of local anaesthetics at sites of inflammation
increases their ionization .
 This leads to lesser penetration into the nerves and, therefore, lesser
activity.
Page  19

20. Factors affecting absorption of local
anaesthetics into the systemic circulation
 Dosage (higher dose = greater probability of systemic absorption)
 Site of injection (injection at areas of large blood supply increase
absorption)
 Presence of vasoconstricting drugs.
Page  20

21. Factors Affect the Reaction of Local
Anesthetics (cont.)
Vasodilation
 Vasoconstrictor is a substance used to keep the anesthetic solution in
place at a longer period and prolongs the action of the drug
 vasoconstrictor delays the absorption which slows down the absorption
into the bloodstream
 Lower vasodilator activity of a local anesthetic leads to a slower
absorption and longer duration of action
 Vasoconstrictor used the naturally hormone called epinephrine
(adrenaline). Epinephrine decreases vasodilator.
Side effects of epinephrine
 Epinephrine circulates the heart, causes the heart beat stronger and
faster, and makes people feel nervous.
Page  21

22. Undesired
systemic effects of
local anesthetics

23. Undesired systemic effects of local anesthetics
 Adverse effects are usually caused by high plasma concentrations of a
local anesthetic drug that result from
– inadvertent intravascular injection,
– excessive dose or rate of injection,
– delayed drug clearance,
– or administration into vascular tissue.
Page  23

24. Undesired systemic effects of local
anesthetics:
Occur due to systemic absorption of large doses due to :
1- accidental intravascular injection
2- Injection of large doses
I- Central nervous system:
-- Stimulation of the CNS caused by inhibition of inhibitory
neuronal activity, producing
1- restlessness
2- tremors that may proceed to convulsions.
-- At high blood concentrations, local anesthetics cause
depression and even respiratory failure..
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25. Undesired effects of local anesthetics
II- Peripheral nervous system:
--- Local anesthetics affect transmission at the neuromuscular junction
producing muscle weakness and tremors.
III- Smooth muscles:
--- Depress contractions of intestine, vascular, and bronchial smooth
muscle.
IV- Allergic reaction:
--- Ester-linked local anesthetics may cause allergic reactions in a
small population of patients due to their metabolism producing para
amino benzoic acid which is allergic .
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26. Undesired effects of local anesthetics
V- Cardiovascular system:
--- Decrease electrical excitability, conduction rate, and force of
contraction in the myocardium.
--- Cause arteriolar dilation.
--- Cocaine differs from the other local anesthetics: it blocks
norepinephrine reuptake, resulting in
vasoconstriction and hypertension, even cardiac arrhythmias.
Page  26

27. Local Anesthesia Allergic shock
 Esters are highly allergenic, their use should be avoided and restricted to
special cases after allergy test.
 There has never been a true, documented allergic reaction to an amine
anesthetic.
 a patient may in fact be allergic only to the bisulfite preservative used to
stabilize the vasoconstrictor.
 If the allergic reaction was not too serious, it may be worth trying again
with either mepivicaine or prilocaine without
vasoconstrictor. Anesthetic manufactures do not use preservatives in
carpules that do not also contain vasoconstrictor.
Page  27

28. Testing for anesthetic allergy using skin test
T.R.U.E. Test®
 This is a patch test that applies 23 allergens to the skin contained in 12
polyester patches. One of the patches contains a mixture of several
anesthetics and is used to test for allergy to local anesthetics in
general. The mixture used includes two ester based anesthetics and one
amine based anesthetic. This mixture of anesthetics is called the "Caine
Mix"
Page  28

29. Signs and symptoms of anesthetics allergic reaction
 The signs and symptoms of allergic reaction include:
– generalized body rash or skin redness
– itching, urticaria (hives)
– broncospasm (difficulty breathing)
– swelling of the throat
– asthma
– abdominal cramping
– irregular heartbeat
– hypotension (low blood pressure)
– swelling of the face and lips (angioneurotic edema)
Page  29

30. Anaphylactic shock
 Fortunately, the majority of allergic reactions to local anesthetics are fairly
mild
 In a very serious anaphylactic reaction, the patient may experience
serious difficulty breathing due to closing down of the bronchioles in the
lungs or swelling in the throat area due to urticaria as well as seriously low
blood pressure leading to anaphylactic shock. This set of events, left
untreated can lead to death.
Page  30

31. Management of anaphylactic shock : 1
 Position the patient on his or her back with the feet elevated.
 Maintain an airway
 If the patient is not breathing on his own, use rescue breathing like you
learned in CPR class. Thanks for Dr. Yasser
 Check the carotid artery for heartbeat and use chest compressions if
necessary.
Page  31

32. Management of anaphylactic shock : 2
 The two drugs that you must have on hand to stabilize a patient in
anaphylactic shock are as follows:
– Epinephrine (adrenalin) 1:1000 subcutaneous injection. It opens the
bronchioles allowing free breathing, increases the blood pressure counteracting
shock and evens out and intensifies the heart beat. Its effects are drastic, but
short lived. The standard dose is 1 mg given in three doses five minutes
apart.
– Benedryl (diphenhydramine) 25-50 mgm injectable. This is an antihistamine
and can also be taken in pill form an hour before the procedure to help
prevent serious allergic reaction before it begins. Injectable diphenhydrimine
which can be administered either subcutaneously, or in the buccal fold if the
dentist is more comfortable with that route.
Page  32

33. Management of anaphylactic shock : 3
 The following drugs are of little use to the dentist during the initial stages
of the emergency since they are generally used by EMS personnel
– Aminophylline This drug opens blocked breathing passages.
– Solu-cortef IV injection. This drug is a corticosteroid and reduces the
generalized allergic inflammatory reactions on a longer term basis. It will not
act rapidly enough to reverse anaphylaxis immediately, but is more of a long
term remedy.
– Wyamine injection. This drug is used to counteract hypotension (low blood
pressure and shock) on a prolonged basis.
Page  33

34. Choose the right Dose
Page  34

35. Preparations
Page  35

36. Minimum Toxic Dose
Page  36

37. Maximum Dose
Page  37

38. Page  38

39. Page  39

40. Dosage guidelines
 Lower concentrations of local anesthetics are typically used for infiltration
anesthesia.
 Variation in local anesthetic dose is dependent on the procedure, the
degree of anesthesia required, and individual patient circumstances.
 Reduced dosage is indicated in debilitated or acutely ill patients; in very
young children or geriatric patients; and in patients with liver disease,
arteriosclerosis, or occlusive arterial disease.
Page  40

41. LA Management of
Special Ptient

42. Children
 Children should have a comfortable experience when going to the
dentist. Local anesthetics are an important tool for
 the control of pain and discomfort during dental treatment
Page  42

43. What local anesthetic
 All local anesthetics have a low margin of safety between the effective
dose and the toxic dose. The lethal dose for many local anesthetics is
only 3 times that of the effective dose.
 Deaths following local anesthetic administration are almost always a result
of overdosage.
 The maximum safe dose of lidocaine for a child is 4.5 mg/kg per dental
appointment.
Page  43

44. What local anesthetic
 Bupivicaine (Marcaine) is an amide local
anesthetic with a high toxic potential, and
should not be used in children. The
duration of anesthesia with bupivicaine
can be as long as 24 hours.
 Lidocaine is less toxic than many other
local anesthetics, because its interactions
with the cardiac sodium channel are “fast
in – fast out,” whereas a local anesthetic
such as bupivicaine is "fast in – slow out.”
 So the best LA to be used with children is
Lidocaine
Page  44

45. What Technique
 Local infiltration of anesthesia is sufficient for all dental treatment
procedures in 90% of cases even in the mandible.
 Nerve bloc is not preferable, just in special cases.
 Local infiltration is less painful when done correctly
Page  45

46. Handicapped Patient
 Several issues arise concerning the use of local anesthesia with this
population. One of these is lip biting
– Consideration should be given to choosing a short-acting local anesthetic to
reduce the possibilityof post-operative trauma from lip biting.
– Another choice would be to avoid mandibular blocks and utilize infiltration,
periodontal ligament
 A second issue with local anesthesia is the inability to determine from a
non-communicative patient when an acceptable level of anesthesia has
been obtained.
– When in doubt second injections and alternative routes (e.g., buccal, mylohyoid,
intraligamentary)
Page  46

47. Handicapped Patient
 An unresolved issue in treating these patients is that severely retarded
patients have a higher pain threshold than the general population.
 Some clinicians therfore choose not to use local anesthetic when the
procedures involve minor restorative needs (e.g.,body pits or minor
occlusal decay).
 These patients are difficult to control. Injecting such a patient can be
extremely difficult and may pose a significant danger to the patient and
the staff.
 One must choose a shorter needle and/or a larger gauge needle which is
less likely to be bent or broken.
 However it is better to use general anesthesia with Handicapped patients.
Page  47

48. Patients receiving anticoagulation or suffering from
bleeding disorders
 oral procedures must be done at the beginning of the day because this
allows more time to deal with immediate re-bleeding problems.
 Also the procedures must be performed early in the week, allowing
delayed re-bleeding episodes, usually occurring after 24-48 h, to be dealt
with during the working weekdays.
 Local anesthetic containing a vasoconstrictor should be administered by
infiltration or by intraligamentary injection wherever practical.
 Regional nerve blocks should be avoided when possible.
 Local vasoconstriction may be encouraged by infiltrating a small amount
of local anesthetic containing adrenaline (epinephrine) close to the site of
surgery.
Page  48

49. Pregnant woman
 Local anesthesia are not teratogenic, and may administered to pregnancy
patient is usual clinical doses.
 Large dose of prilocaine are know to cause methemoglobinemia which
could cause maternal & fetal hypoxia.
 Local vasoconstriction
– Delay uptake from the site of injection
– Increase the effectiveness & duration
There is no specific contraindication to these vasoconstrictors in a
pregnant patient although it is prudent to use minimal effective dose.
Page  49

50. Pregnant woman
• Lidocaine + vasoconstrictor: most common local anesthetic used in
dentistry extensively used in pregnancy with no proven ill effects
• accidental intravascular injections of lidocaine pass through the placenta
but the concentrations are too low to harm fetus
• Drug classes:
B: lidocaine, prilocaine, etidocaine
C: mepivacaine, bupivacaine
Not yet assigned: Procaine
• The need for careful Hx taking & for aspiration & slow injected technique
is obvious
Page  50

51. For Information :
Pregnancy drug Clases
Medications are grouped into 1 of 5 categories based on the potential for
producing birth defects. The categories are A, B, C, D and X. Generally
speaking, drugs that fall into either class A or B are considered safe and
are routinely used. There may be exceptions.
Category A: Controlled studies in pregnant women fail to demonstrate a
risk to the fetus in the first trimester with no evidence of risk in later
trimesters. The possibility of harm appears remote.
Category B: Presumed safety based on animal studies, with no
controlled studies in pregnant women, or animal studies have shown an
adverse effect that was not confirmed in controlled studies in women in
the first trimester and there is no evidence of a risk in later trimesters.
Category C: Studies in women and animals are not
available or studies in animals have revealed adverse effects on the
fetus and there are no controlled studies in women. Drugs should be
given only if the potential benefits justify the potential risk to the fetus.
Category D: There is positive evidence of human fetal risk (unsafe),
however in some cases such as a life-threatening illness the potential
risk may be justified if there are no other alternatives.
Category X: Highly unsafe: risk of use outweighs any potential
benefit. Drugs in this category are contraindicated in women who are or
may become pregnant.
Page  51

52. GERIATRIC PATIENT
 When choosing an anesthetic, we are largely concerned with the effect of
the anesthetic agent upon the patient's cardiovascular and respiratory
systems.
 increased tissue sensitivity to drugs acting on the CNS
 Decreased hepatic size and blood flow may reduce hepatic metabolism of
drugs
 hypertension is common and can reduce renal function
 Same prevention procedures used with children
Page  52

53. LIVER DISORDERS
 Advanced liver diseases include:
Liver cirrhosis - Jaundice
 Potential complications:
1. Impaired drug detoxication e.g. sedative, analgesics, general
anesthesia.
2. Bleeding disorders ( decrease clotting factors, excess fibrinolysis,
impaired vitamin K absorption).
3. Transmission of viral hepatitis.
Management
Avoid LA metabolized in liver: Amides (Lidocaine, Mepicaine), esters
should be used
Page  53

54. Drug-Drug Interaction
 Local anesthetics and vasoconstrictor may interact with other prescribed
drugs.
 list of administrated drugs to the patient can play a role in the local
anesthetic choice.
Page  54

55. References
 Calatayud Jesús and González Ángel. History of the Development and Evolution of
Local Anesthesia Since the Coca Leaf. © 2003 American Society of Anesthesiologists
Volume 98(6) June 2003 pp 1503-1508.
 Peter C. Meltzer, Shanghao Liu, Heather S. Blanchette, Paul Blundell, Bertha K.
Madras. Design and Synthesis of an Irreversible Dopamine-Sparing Cocaine
Antagonist. @ Bioorganic & Medicinal Chemistry Volume 10, Issue 11 , November
2002, Pages 3583-3591
 Shigeki Isomura, Timothy Z. Hoffman, Peter Wirsching, and Kim D. Janda. Synthesis,
Properties, and Reactivity of Cocaine Benzoylthio Ester Possessing the Cocaine
Absolute Configuration. J. AM. CHEM. SOC. 2002, Issue 124, p.3661-3668
 Mazoit, Jean-Xavier; Dalens, Bernard J. Pharmacokinetics of local anesthetics in
infants and children. Clinical Pharmacokinetics (2004), 43(1), 17-32.
 Alejandro A. Nava-Ocampo and Angelica M. Bello-Ramirez. Lipophilicity Affects the
Pharmacokinetics and Toxicity of Local Anaesthetic Agents Administered by Caudal
Block. Clinical and Experimental Pharmacology and Physiology (2004) 31, 116-118.
 Don R Revis, Jr. Local Anesthetics. October 14,2004: (Medline)
http://www.emedicine.com/ent/topic20.htm
Page  55

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