Slide 1. Slide 2. Slide 3. Local Anesthetics. Local Anesthetics. Lesson 9.1. History and Purpose of Anesthetics. Chapter 9

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1 Slide 1 Local Anesthetics Chapter 9 1 Slide 2 Lesson 9.1 History and Purpose of Anesthetics 1. Discuss the history and reasons for the use of local anesthetics in dentistry, including: List the properties an ideal local anesthetic would possess. Describe the importance of understanding the chemistry involved in local anesthetic agents. 2. Explain the mechanism of action, pharmacokinetics, pharmacologic effects, and adverse reactions of local anesthetics. 2 Slide 3 History Ideal local anesthetic Chemistry Mechanism of action Pharmacokinetics Pharmacologic effects Adverse reactions Local Anesthetics Compositions of local anesthetic solutions Local anesthetic agents Vasoconstrictors Choice of local anesthetic Topical anesthetics Doses of local anesthetic and vasoconstrictor 3

2 Slide 4 History 1860 Niemann isolated cocaine 1884 Koller Sigmund Freud 1905 Einhorn synthesized procaine 1952 Amide lidocaine (Xylocaine) 1960 Mepivacaine (Carbocaine) Bupivacaine (Marcaine) 4 Slide 5 Properties of the Ideal Local Anesthetic Potent local anesthesia Reversible local anesthesia Absence of local reactions Absence of allergic reactions Rapid onset Satisfactory duration Adequate tissue penetration Low cost Stability in solution Sterilization by autoclave Ease of metabolism and excretion 5 Slide 6 Chemistry Esters Amides Other Aromatic nucleus (R) Linkage (ester or amide, followed by aliphatic chain, R) Amino group 6

3 Slide 7 Mechanism of Action 7 Slide 8 Mechanism of Action (Cont.) Free base Salt Viscid liquids or amorphous solids Fat soluble Unstable Alkaline Uncharged, nonionized Penetrates nerve tissue Form present in tissue (ph 7.4) Crystalline solids Water soluble Stable Acidic Charged, cation (ionized) Active form at site of action Form present in dental cartridge (ph ) 8 Slide 9 Pharmacokinetics Absorption depends on its route Rate of absorption depends on vascularity of the tissues Degree of inflammation present Vasodilating properties of the local anesthetic agent Presence of heat Use of massage 9

4 Slide 10 Pharmacokinetics (Cont.) The vasoconstrictor Reduces the blood supply to the area Limits systemic absorption Reduces systemic toxicity 10 Slide 11 Pharmacokinetics (Cont.) Mucous membranes or denuded surface = increased absorption Absorption is also determined by the proportion of the agent present in the freebase form (nonionized) 11 Slide 12 Pharmacokinetics (Cont.) Highly vascular organs have higher concentrations of anesthetics Local anesthetics cross the placenta and blood-brain barrier Lipid solubility affects the potency of the agent Bupivacaine 0.5% is about 10 times more lipid soluble than lidocaine used as a 2% solution 12

5 Slide 13 Pharmacokinetics (Cont.) Esters are hydrolyzed by plasma pseudocholinesterases and liver esterases Procaine is hydrolyzed to para-aminobenzoic acid (PABA) Amides are metabolized by liver Prilocaine > orthotoluidine > methemoglobinemia Cimetidine > reduce hepatic blood flow 13 Slide 14 Pharmacokinetics (Cont.) Metabolites and some unchanged drug of both esters and amides are excreted by the kidneys Both parent drug and metabolites can accumulate with end-stage renal disease 14 Slide 15 Pharmacologic Effects Peripheral Nerve Conduction (Blocker) Autonomic Cold Warmth Pain Touch Pressure Vibration Proprioception Motor 15

6 Slide 16 Pharmacologic Effects Direct effect on cardiac muscle Block cardiac sodium channels Depress abnormal cardiac pacemaker activity, excitability, and conduction Depress strength of cardiac contraction Produce arteriolar dilation Treatment of arrhythmias 16 Slide 17 Adverse Reactions Drug: Inherent toxicity and amount of vasodilation Concentration Route of administration Rate of injection Vascularity Patient s weight Rate of metabolism and excretion 17 Slide 18 Adverse Reaction Toxicity Affecting the CNS System CNS stimulation Restlessness Tremors Convulsions CNS depression Respiratory and cardiovascular depression Coma follows 18

7 Slide 19 Adverse Reaction Toxicity Affecting Cardiovascular System Myocardial depression Cardiac arrest with peripheral vasodilation Usual concentrations not expected to result in any of these adverse reactions 19 Slide 20 Adverse Reaction Local Effects Result of injection technique Result of administration of an excessive volume too quickly Hematoma 20 Slide 21 Adverse Reaction Malignant Hyperthermia An inherited disease that is transmitted as an autosomal-dominant gene Acute rise in calcium > muscular rigidity, metabolic acidosis, and extremely high fever Treatment includes supportive measures and the administration of dantrolene (Dantrium) Halothane & succinylcholine are contraindicated 21

8 Slide 22 Adverse Reaction Pregnancy & Nursing Considerations Elective dental treatment should be rendered before a patient becomes pregnant Lidocaine FDA pregnancy category B Prilocaine FDA pregnancy category B Mepivacaine FDA pregnancy category C Articaine FDA pregnancy category C Bupivacaine FDA pregnancy category C 22 Slide 23 Adverse Reaction Allergy Obtain allergy history Esters have a much greater allergic potential Unknown if amides produce allergic reactions Diphenhydramine (Benadryl) 1% plus 1:100,000 Methylparaben Sulfite 23 Slide 24 Lesson 9.2 Local Anesthetic Agents and Their Use in Dentistry 3. Describe the composition of each of the drugs used in local anesthetic solutions and summarize the factors involved in the choice of a local anesthetic. 4. Briefly discuss the use, types, and doses of topical anesthetics used in dentistry. 24

9 Slide 25 Composition of Local Anesthetic Solutions Vasoconstrictor Epinephrine Antioxidant Sodium metabisulfite, sodium bisulfite, acetone sodium bisulfite Sodium hydroxide Sodium chloride Methylparaben and propylparaben 25 Slide 26 Local Anesthetic Agents: Lidocaine (Xylocaine, Octocaine) Introduced in 1948 Rapid onset Good distribution Lidocaine 2% with vasoconstrictor medium duration 26 Slide 27 Local Anesthetic Agents: Mepivacaine (Carbocaine, Polocaine, Isocaine) Introduced in 1960 Its rate of onset, duration, potency, and toxicity are similar to those of lidocaine Not effective topically Used for infiltration, block, spinal, epidural, and caudal anesthesia Mepivacaine 2% with 1:20,000 levonordephrin (Neo-Cobefrin) as a vasoconstrictor 27

10 Slide 28 Local Anesthetic Agents: Prilocaine (Citanest, Citanest Forte) Related chemically & pharmacologically to lidocaine and mepivacaine Toluidine derivative Less potent & less toxic than lidocaine Has a slightly longer duration of action Orthotoluidine > methemoglobinemia Prilocaine 4% with/without 1:200,000 epinephrine 28 Slide 29 Local Anesthetic Agents: Bupivacaine (Marcaine) Related to lidocaine and mepivacaine More potent & toxic Advantage: Prolonged duration of action Bupivacaine 0.5% with 1:200,000 epinephrine 29 Slide 30 Local Anesthetic Agents: Articaine (Septocaine) Approved for use in U.S. in 2000 Derived from thiophene Greater lipid solubility Hydrolyzed by plasma esterase Metabolized mainly in blood Excreted by kidneys Half-life is 20 minutes May cause methemoglobinemia Paresthesia 30

11 Slide 31 Local Anesthetic Agents: Articaine (Septocaine) (Cont.) Used for local, infiltrative, and conductive anesthesia Articaine 4% 1:100,000 epinephrine in a 1.7- ml cartridge unlike the more common 1.8-ml dental cartridge Articaine 4% 1:200, Slide 32 Local Anesthetic Agents: Esters No esters are currently available in a dental cartridge Benzocaine: Commonly used topically 32 Slide 33 Local Anesthetic Agents: Procaine (Novocain) PABA ester Used as an antiarrhythmic agent Combined with penicillin to form procaine penicillin G Procaine is not used in dentistry today 33

12 Slide 34 Local Anesthetic Agents: Tetracaine (Pontocaine) An ester of PABA Slow onset Long duration Estimated to have at least 10 times the potency and toxicity of procaine Available in various sprays, solutions, and ointments for topical application 34 Slide 35 Other Dyclonine (Dyclone) Topical local anesthetic Neither an ester nor an amide Its side effects similar to those of other local anesthetics Onset is 2 to 10 minutes Duration is 30 to 60 minutes 35 Slide 36 Vasoconstrictors Prolong the duration of action Increase the depth of anesthesia Delay systemic absorption Reduce the toxic effect in the systemic circulation Reduce the bleeding in the area of injection and improve visibility at surgical site 36

13 Slide 37 Vasoconstrictors (Cont.) The decision about whether epinephrine should be used is made by weighing the risks and benefits 37 Slide 38 Vasoconstrictors: Drug Interactions Tricyclic antidepressants Administration of epinephrine may produce an exaggerated increase in pressor response Nonselective β-blockers Administration of epinephrine may produce hypertension and reflex bradycardia 38 Slide 39 Vasoconstrictors: Drug Interactions (Cont.) Monoamine oxidase inhibitors (MAOIs) Phenothiazines 39

14 Slide 40 Choice of Local Anesthetic 40 Slide 41 Topical Anesthetics Benzocaine, an ester, is the most commonly used topical anesthetic Lidocaine, an amide, is the second most commonly used 41 Slide 42 Topical Anesthetics: Lidocaine (Xylocaine) Available as base or hydrochloride salt The base is preferred when large areas of the mucosal surface are ulcerated, abraded, denuded, or erythematous The hydrochloride salt is water soluble and penetrates the tissue better 42

15 Slide 43 Topical Anesthetics: Lidocaine and Prilocaine (Oraquix) Amides: Lidocaine and prilocaine (injectionfree local anesthesia) Duration of action 20 minutes Onset of action 30 seconds 43 Slide 44 Questions? 44