Questions and Answers
Local anesthetics are drugs that suppress ___ by blocking impulse conduction along axons.
pain
Local anesthetics stop nerve conduction by blocking ___ channels in the axon membrane.
sodium
What is the greatest advantage of local anesthesia compared to inhalation anesthesia?
With local anesthesia, pain can be suppressed without causing generalized depression of the entire nervous system.
What are the two major groups of local anesthetics?
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Ester-type agents are represented by ___.
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Amide-type agents are represented by ___.
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What are the two main ways that ester-type and amide-type agents differ?
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___ of local anesthesia occurs as molecules of anesthetic diffuse out of neurons and are carried away in the blood.
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Local anesthetics frequently are administered in combination with a ___, which reduces local blood flow and delays systemic absorption of the anesthetic.
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What are the two benefits of delaying the systemic absorption of local anesthesia?
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Ester-type local anesthetics are metabolized in the blood by enzymes known as ___.
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Amide-type anesthetics are metabolized by enzymes in the ___.
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Allergic reactions occur more often with which type of local anesthetic?
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Ester-type anesthetics (procaine) occasionally cause ___ and are inactivated by esterases in the blood.
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Ester-type anesthetics are inactivated by ___ in the blood.
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Amide-type anesthetics (lidocaine) rarely cause ___ and are inactivated by enzymes in the liver.
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Amide-type anesthetics are inactivated by ___ in the liver.
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Absorbed local anesthetics can ___ excitability in the myocardium and conducting system.
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What are four signs and symptoms of the effect of local anesthetics on the heart?
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What is a sign of the effect of local anesthetics on the blood vessels?
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Can local anesthetics cross the placenta?
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Local anesthetics ___ labor.
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What was the first local anesthetic?
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Cocaine is a ___-type anesthetic.
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What are the three most common surface anesthetics?
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What are four methods for patients to minimize the amount of topical anesthetics absorbed and minimize risks?
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Which type of neurons are blocked more rapidly by local anesthetics?
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Termination of local anesthesia is determined in large part by regional ___.
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What are the main concerns with systemic toxicity of local anesthetics?
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What are some CNS effects of systemic toxicity of local anesthetics?
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What are some ways to reduce the risk of systemic toxicity of local anesthetics?
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Study Notes
Local Anesthetics Overview
- Local anesthetics suppress pain by blocking impulse conduction along axons.
- Blockage of sodium channels in the axon membrane is crucial for stopping nerve conduction.
Advantages and Classifications
- Local anesthesia provides pain relief without causing generalized nervous system depression, unlike inhalation anesthesia.
- Two main types of local anesthetics:
- Ester-type (e.g., procaine)
- Amide-type (e.g., lidocaine)
Differences Between Ester and Amide Types
- Differ in two key aspects:
- Method of inactivation
- Potential for allergic responses
Mechanisms and Administration
- Termination of local anesthesia occurs as the anesthetic molecules diffuse out of neurons and are absorbed into the bloodstream.
- Often administered with a vasoconstrictor to reduce blood flow, delaying systemic absorption.
Benefits of Delaying Systemic Absorption
- Prolongs anesthesia duration.
- Reduces risk of toxicity.
Metabolism of Anesthetics
- Ester-type anesthetics are metabolized by enzymes called esterases in the blood.
- Amide-type anesthetics undergo metabolism in the liver by liver enzymes.
Allergic Reactions
- Ester-type anesthetics are more likely to cause allergic reactions than amide-type.
- Procaine can lead to allergic reactions due to its metabolism by esterases.
Cardiac and Vascular Effects
- Absorbed local anesthetics can suppress myocardial and conducting system excitability.
- Signs of cardiac effects include bradycardia, heart block, reduced contractile force, and possible cardiac arrest.
- Hypotension is a noted effect on blood vessels.
Placental Transfer and Labor
- Local anesthetics can cross the placenta and may prolong labor.
Historical Context
- Cocaine was the first local anesthetic, categorized as an ester-type.
Surface Anesthetics
- Common surface anesthetics include lidocaine, tetracaine, and cocaine.
Minimizing Topical Anesthetic Absorption
- To reduce risks:
- Use the smallest effective amount.
- Avoid large area applications.
- Exclude broken or irritated skin in applications.
- Refrain from strenuous exercise, wrapping the site, or heating, as these increase absorption.
Neuron Sensitivity
- Smaller, nonmyelinated neurons are blocked more rapidly than larger, myelinated ones.
Systemic Toxicity Concerns
- Key concerns include cardiac dysrhythmias and central nervous system effects.
- CNS effects of toxicity may include seizures, unconsciousness, and coma.
Risk Reduction Strategies
- Minimize systemic toxicity by using smaller amounts, avoiding large areas, and not applying to broken skin.
- Avoid strenuous exercise and heat application post-application.
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Test your knowledge on local anesthetics through these flashcards. Learn about their functions, advantages, and mechanisms of action. This quiz is ideal for students in pharmacology or those preparing for medical exams.