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Contents of the dental carpule - Pharmacology of local anesthesia Contents of the dental carpule - Pharmacology of local anesthesia Presentation Transcript

  • In the name of Allah, Most Gracious, ‫ﺑ ﻢ ﷲ ﺮ ﻦ ﺮﺣ ﻢ‬ ِ ‫ِﺴْ ِ ا ِ اﻟ ﱠﺣْﻤ ِ اﻟ ﱠ ِﯿ‬ Most Merciful And swell not thy cheek ‫وﻟ ﺗﺼﻌ ﺧ ﱠك‬ َ ‫ََﺎ ُ َ ﱢﺮْ َﺪ‬ (for pride) at men, nor ‫ﻟ ﻨ س وﻟ ﺗ ﺶ‬ ِ ْ‫ِﻠ ﱠﺎ ِ ََﺎ َﻤ‬walk in insolence through ‫ﺄ ض ﻣﺮ ﺎ‬ ً‫ِﻲ اﻟَْرْ ِ َ َﺣ‬ ‫ﻓ‬the earth; for Allah loveth ‫إن ﻠﻪ ﻟ ﻳﺤﺐ‬ ‫ِ ﱠ اﻟ ﱠ َ َﺎ ُ ِ ﱡ‬not any arrogant boaster ‫ﻛﻞ ﻣ ﺘ ل ﻓﺨ ر‬ ٍ ‫ُ ﱠ ُﺨْ َﺎ ٍ َ ُﻮ‬ Luqmân 18 [18 : ‫]ﻟﻘﻤﺎن‬
  • PHARMACOLOGY OF LOCAL ANESTHESIA Dr. Hesham El-Hawary hesham@elhawarydentalclinic.com
  • Pharmacology of Local AnesthesiaCONSTITUENTS OF THE ANESTHETIC CARPULE
  • Anesthesia with V.C.1. Local anesthetic agent ( L.A.)2. Vasoconstrictor agent ( V.C.)3. Preservative for V.C. agent (anti- oxidant)4. Vehicle to make solution isotonic ( 0.9%NaCl)
  • 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.) isotonic3. Preservative for V.C. ( 0.9%NaCl) agent (anti- oxidant)4. Vehicle to make solution isotonic ( 0.9%NaCl)
  • Keep in mind:• The main agent in the 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
  • Pharmacology of Local AnesthesiaTHE LOCAL ANESTHETIC DRUG
  • Local anesthetic drugs• Drugs temporary interrupt nerve conduction when absorbed into it and have little or no irritating effect when injected• They are all synthetic compounds except the cocaine
  • Properties of ideal anesthetic agent1. Reversible action2. Nonirritant3. Produce no secondary local reaction (No allergic reaction)4. No systemic toxicity5. Rapid onset6. Sufficient duration7. Potent8. Sufficient penetrating properties9. Stable in solution and undergo biotransformation in body10. Can be sterilized without deterioration11. Not interfere with healing of local tissues12. Have vasoconstrictor action or compatible with V.C.13. Not expensive
  • Common properties of injectable LA Agents1. Form salts with strong acids which is water soluble2. When injected in the body (alkali) • Hydrolyzed by plasma proteins to free the alkaloid base which is lipid soluble • Undergo biotransformation3. Affect the nerve conduction and have reversible action4. Compatible with vasoconstrictors5. Not or slightly irritant to the tissue in the concentration used6. Capable of producing toxic effect when sufficient high plasma concentration is reached
  • 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
  • Pharmacokinetics of local anesthetics Uptake Potency Duration Biotransformation Excretion
  • 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
  • Potency• The majority of local anesthetics are tertiary amines• Few local anesthetics are secondary amines as Procaine• NH3 → NR3• Local anesthetic agent is prepared in the carpule in the form of hydrochloride salt of tertiary amine ( NR3 ̶ HCL)
  • • 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
  • • 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)
  • DurationThe following factors affect both duration & depth of anesthetic action :• Factors related to the anesthesia – Lipid solubility – Concentration and type of the drug – Presence or absence of vaconstrictor or vasoconstriction effect – Duration of exposure
  • • 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
  • 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)
  • 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
  • Local Anesthetic Agents
  • Local anesthetic agentsEster Group Amide Group
  • 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
  • Amides• Lidocaine• Bupivacaine• Articaine• Mepivacaine• Prilocaine• Etidocaine• Ropivacaine
  • 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
  • Contrast between ester & amide groups Features Esters Amides Chemical bond Ester bond Amide bond Procaine LidocaineCommon example ( Novocaine) ( Xylocaine) Allergy Low Very low Plasma Liver Metabolism in pseudo- microsomal cholinesterase enzymes enzyme
  • 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 / without VC
  • unacainetetracaine buycaine procaine articaine marcainemepivicaine Lidocaine Metabolism Excretion duration Topical Allergy Onset forms Type VD
  • Maximum doses of L.A. agents
  • L.A. agent Max. dose Normal dose Lidocaine 300 mg 4.4 mg / kgMepivacaine 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
  • Dilution of L.A. agents
  • • 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• 2 % means 2 g / 100 ml• 2 % means 2000 mg / 100 ml• 2000 mg – 100 ml• ? mg - 1.8 ml• ? = 1.8 x 2000 / 100 = 36 mg• Therefore carpule of 1.8 ml contains 36 mg solution
  • The Vasoconstrictor
  • Advantages It causes V.C. of B.V. that1. 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 procedure2. 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 drug3. It stimulate the heart Thus counteract the depressant effect of the local anesthetic agent on the heart
  • Contra-Indications1. 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 pressure3. 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)
  • Contra-Indications Cont.4. Pregnancy: Because the V.C. causes uterine contraction & may causes abortion5. Extraction of teeth with chronic peri-apical sepsis: Because V.C. decrease blood flow to the tissues & may lead to dry socket5. Hyperthyroidism (toxic goiter): Because V.C. specially adrenaline may cause thyroid crisis & sudden death
  • Types of V.C.1. Epinephrine ( adrenaline)2. Nor- Epinephrine ( nor - adrenaline)3. Neo- cobefrin (levonordefrin)4. Phenylephrine (neosynephrine)5. Felypressin (octapressin)
  • Dilution of V.C. Cont.The dilution of V.C. 1: 1000 meansthat there is one gram (1000 mg) ofthe V.C. in 1000 ml ( 1 liter) of thesolution, or in other words 1.0 mg/mlof the solution
  • • Examples1: 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
  • • Examples1: 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
  • A & B adrenergic receptors• A receptors – Vasodilatation of cardiac coronaries – Peripheral vasoconstriction• B1 receptors – Increase cardiac output – Increase heart rate• B2 receptors – Broncho-dilatation
  • Epinephrine Nor Levo Phenyl Felypressen Epinephrine nordefrine ephrineActionCVSRSCNSPotencyToxicityStabilityCI
  • Maximum Doses Of V.C. V.C. Max. dose Concentration epinephrine 0.2mg 20ml 1 : 100 000nor epinephrine 0.34mg 10ml 1 : 100 000levonordefrin 1.0mg 20ml 1 : 20 000Phenylephrine 4.0mg 20ml 1 : 2 500 felypressin 0.27 IU 9ml 0.03 IU
  • Vehicle
  • • 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)
  • • 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 occurs2. 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
  • • 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 occurs2. Less profound anesthesia: As concentration of the injected solution decreased due gain of water ( dilution of the injected solution in the area)
  • Preservative
  • • 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
  • Topical anesthetics
  • 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
  • Thank You Hesham El-Hawary www.elhawarydentalclinic.com