Local Anesthetics Overview
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Questions and Answers

Which classification of local anesthetics is based on their chemical structure?

  • Topical and Injectable
  • Esters and Amides (correct)
  • Short, Intermediate, and Long duration
  • Biotoxins and Nerve inhibitors

    • Which local anesthetic is known for its long duration of action?

  • Prilocaine
  • Bupivacaine (correct)
  • Lidocaine
  • Mepivacaine

    • What is the common mechanism of action for all local anesthetics?

  • Increasing neurotransmitter release
  • Enhancing nerve impulses
  • Blocking calcium channels
  • Blocking Na channels (correct)

    • Which of the following local anesthetics is an example of a benzoic acid ester?

    <p>Cocaine</p> Signup and view all the answers

    Which local anesthetic is typically used in dental procedures for its intermediate duration?

    <p>Lidocaine</p> Signup and view all the answers

    What is the role of vasoconstrictors like epinephrine in local anesthesia?

    <p>Reduce bleeding at the site</p> Signup and view all the answers

    Which local anesthetic has a chemical structure classified as a quaternary ammonium analog?

    <p>Articaine</p> Signup and view all the answers

    What defines local anesthetics with a short duration of action?

    <p>They are quickly metabolized</p> Signup and view all the answers

    Which of the following local anesthetics is considered an ester local anesthetic?

    <p>Benzocaine</p> Signup and view all the answers

    What is the primary route and time for achieving peak blood level of a local anesthetic when administered intravenously?

    <p>Intravenous, 1 minute</p> Signup and view all the answers

    In terms of distribution, which type of tissue initially has higher blood levels of local anesthetics?

    <p>Highly perfused organs</p> Signup and view all the answers

    Which local anesthetic is primarily metabolized in the liver?

    <p>Lidocaine</p> Signup and view all the answers

    What is the primary excretory organ for local anesthetics and their metabolites?

    <p>Kidneys</p> Signup and view all the answers

    Which local anesthetic is known for being a surface anesthetic that is soluble?

    <p>Cocaine</p> Signup and view all the answers

    Which of the following statements about the pharmacological action of local anesthetics is TRUE?

    <p>Most local anesthetics produce vasodilation.</p> Signup and view all the answers

    The enzyme responsible for hydrolyzing ester local anesthetics is known as what?

    <p>Pseudocholinesterase</p> Signup and view all the answers

    What is the effect of low blood levels of local anesthetics on the central nervous system?

    <p>They have no effects on the CNS.</p> Signup and view all the answers

    Which local anesthetic is classified as an ester?

    <p>Procaine</p> Signup and view all the answers

    What is the main function of sodium chloride in a local anesthetic solution?

    <p>Maintains isotonicity of the solution.</p> Signup and view all the answers

    Which of these local anesthetics has the greatest vasodilating properties?

    <p>Procaine</p> Signup and view all the answers

    What happens at overdose levels of local anesthetics in the respiratory system?

    <p>Respiratory arrest.</p> Signup and view all the answers

    What is a potential cardiovascular effect of high blood levels of local anesthetics?

    <p>Hypotension.</p> Signup and view all the answers

    Which local anesthetic has an onset of action of 6 to 10 minutes?

    <p>Procaine</p> Signup and view all the answers

    Which component is used in local anesthetic solutions to act as an antioxidant for vasoconstrictors?

    <p>Sodium meta bisulfite</p> Signup and view all the answers

    What is the maximum recommended dose of mepivacaine for adults?

    <p>6.6 mg/kg body weight</p> Signup and view all the answers

    What is the duration of pulpal anesthesia for 2% mepivacaine?

    <p>60 minutes</p> Signup and view all the answers

    Which of the following is a contraindication for the use of prilocaine?

    <p>Idiopathic or congenital methemoglobinemia</p> Signup and view all the answers

    Which vasoconstrictor produces greater hemostasis when used with mepivacaine?

    <p>Epinephrine</p> Signup and view all the answers

    What is the classification of prilocaine?

    <p>Amide</p> Signup and view all the answers

    What is the half-life classification of procaine compared to amide anesthetics?

    <p>Shorter than amide anesthetics</p> Signup and view all the answers

    What is a recommended maximum dose of procaine combined with propoxycaine for adult patients?

    <p>6.6 mg/kg</p> Signup and view all the answers

    Which of the following properties does lidocaine exhibit compared to procaine?

    <p>Greater potency</p> Signup and view all the answers

    During metabolism, lidocaine produces which potentially toxic local anesthetic?

    <p>Xylidide</p> Signup and view all the answers

    How is mepivacaine primarily excreted from the body?

    <p>In urine as unchanged anesthetic</p> Signup and view all the answers

    What is the effect of epinephrine when used with 2% lidocaine for hemostasis?

    <p>Reduces systemic absorption of lidocaine</p> Signup and view all the answers

    Which classification does lidocaine belong to?

    <p>Amide</p> Signup and view all the answers

    What is the vasodilating property of mepivacaine compared to other local anesthetics?

    <p>Slight vasodilator</p> Signup and view all the answers

    Study Notes

    Local Anesthetics

    • Local anesthetics reduce pain during medical procedures.
    • They were used as early as 1884.
    • Cocaine was the first local anesthetic used in 1886.
    • Procaine was introduced in 1905, and other local anesthetics followed in 1946.
    • Local anesthetics are classified based on their chemical structure, duration of action, biological site, and mode of application.

    Chemical Structure

    • Local anesthetics are categorized as either esters or amides.
    • Esters include benzocaine, cocaine, procaine, and propoxycaine.
    • Amides include articaine, bupivacaine, lidocaine, mepivacaine, and prilocaine.

    Duration of Action

    • Local anesthetics can be short, intermediate, or long acting.
    • Short-acting: Mepivacaine HCl 3%.
    • Intermediate-acting: Lidocaine HCl 2% + epinephrine 1:100,000.
    • Long-acting: Bupivacaine HCl 0.5% + epinephrine 1:200,000 and etidocaine.

    Biological Site and Mode of Action

    • Local anesthetics block sodium channels on the nerve cell membrane to prevent nerve impulse conduction.

    Mode of Application

    • Local anesthetics can be injected (e.g., procaine, lidocaine) or used topically.
    • Topical anesthetics can be soluble (e.g., cocaine, lidocaine) or insoluble (e.g., benzocaine).

    Pharmacokinetics

    • Uptake: Local anesthetics are absorbed into the bloodstream and distributed throughout the body.
    • Distribution: Highly perfused organs (e.g., brain, liver, kidneys, lungs, spleen) receive the anesthetic first.
    • Metabolism:
      • Esters are hydrolyzed in the blood plasma by pseudocholinesterase.
      • Amides are metabolized in the liver.
    • Excretion: Local anesthetics and their metabolites are primarily excreted through the kidneys.

    Systemic Actions

    • Central Nervous System: Local anesthetics can cross the blood-brain barrier.
      • Low blood levels do not affect the CNS.
      • High blood levels can lead to generalized tonic-clonic convulsions.
    • Cardiovascular System: Local anesthetics produce myocardial depression.
      • They decrease electrical excitability of the myocardium.
      • They reduce the force of contraction.
      • They can lead to hypotension due to vasodilation.
    • Respiratory System: Local anesthetics can have a direct relaxant effect on bronchial smooth muscles.
      • Overdose levels can lead to respiratory arrest.

    Composition of Local Anesthetics Solutions

    • Local anesthetics solutions contain:
      • Local anesthetic drug: Blocks nerve conduction.
      • Sodium chloride: Makes the solution isotonic to prevent cell damage.
      • Sterile water: Provides volume.
      • Vasoconstrictor (e.g., epinephrine): Increases the depth and duration of anesthesia. It also reduces the absorption of local anesthetics, reducing toxicity.
      • Sodium meta bisulfite: An antioxidant for the vasoconstrictor.
      • Methyl paraben: A bacteriostatic agent.

    Procaine

    • Classification: Ester.
    • Potency: 1 (procaine = 1).
    • Toxicity: 1 (procaine = 1).
    • Onset of action: 6 to 10 minutes.
    • Anesthetic half-life: 0.1 hour (6 minutes).
    • Effective dental concentration: 2% to 4%.
    • Uses:
      • Management of accidental intraarterial injection.
      • Breaking arteriospasm.
    • It produces the greatest vasodilation of all local anesthetics.

    Propoxycaine

    • This agent is usually combined with procaine for a more rapid onset and prolonged anesthesia.
    • It is not used alone due to high toxicity.
    • Combined with procaine when amide agents are contraindicated.

    Lidocaine

    • Classification: Amide.
    • Potency: 2 (compared to procaine).
    • Toxicity: 2 (compared to procaine).
    • Effective dental concentration: 2% with Epinephrine.
    • Onset of action: Rapid, 3 to 5 minutes.
    • Pulpal anesthesia (with 1:100,000 epinephrine): 60 minutes (intermediate duration).
    • Soft tissue anesthesia (with 1:100,000 epinephrine): 180-300 minutes (3-5 hours).
    • Maximum recommended dose (with epinephrine): Adult: 7.0 mg/kg body weight.
    • Pregnancy classification: B (considered safe during pregnancy).

    Mepivacaine

    • Classification: Amide.
    • Potency: 2 (procaine = 1; lidocaine = 2).
    • Toxicity: 1.5 to 2 (procaine = 1; lidocaine = 2).
    • Effective dental concentration: 3% plain (short duration) or 2% with a vasoconstrictor (intermediate duration).
    • Onset of action: Rapid, 3 to 5 minutes.
    • Pulpal anesthesia: 20-40 minutes for 3% and 60 minutes for 2%.
    • Soft tissue anesthesia: 2-3 hours for 3% and 3-5 hours for 2%.
    • Maximum recommended dose: Adult: 6.6 mg/kg body weight.
    • Pregnancy classification: C (not considered safe).
    • 3% mepivacaine plain is recommended for pediatric & geriatric patients or shorter dental procedures.
    • 2% mepivacaine with vasoconstrictors (e.g. levonordefrin, epinephrine) provides intermediate duration.

    Prilocaine

    • Classification: Amide.
    • Prilocaine 4% with or without epinephrine (1:200,000) is used for patients with epinephrine sensitivity.
    • It is considered safe due to its fast biotransformation.
    • Maximum recommended dose: 8 mg/kg.
    • Contraindications:
      • Idiopathic or congenital methemoglobinemia.
      • Hemoglobinopathies (e.g., sickle cell anemia).
      • Cardiac or respiratory failure.

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    Pharmacology of Local Anesthetics - Part 1 PDF

    Description

    This quiz explores the fundamentals of local anesthetics, including their historical development and classification. You'll learn about different chemical structures, duration of action, and their biological effects. Test your knowledge on these essential medical agents.

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