Drug Classifications: Local Anesthetics Flashcards

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?

(1) ester-type (2) amide-type Signup and view all the answers

Ester-type agents are represented by ___.

procaine Signup and view all the answers

Amide-type agents are represented by ___.

lidocaine Signup and view all the answers

What are the two main ways that ester-type and amide-type agents differ?

(1) method of inactivation (2) promotion of allergic responses Signup and view all the answers

___ of local anesthesia occurs as molecules of anesthetic diffuse out of neurons and are carried away in the blood.

Termination Signup and view all the answers

Local anesthetics frequently are administered in combination with a ___, which reduces local blood flow and delays systemic absorption of the anesthetic.

vasoconstrictor Signup and view all the answers

What are the two benefits of delaying the systemic absorption of local anesthesia?

(1) prolongs anesthesia (2) reduces the risk of toxicity Signup and view all the answers

Ester-type local anesthetics are metabolized in the blood by enzymes known as ___.

esterases Signup and view all the answers

Amide-type anesthetics are metabolized by enzymes in the ___.

liver Signup and view all the answers

Allergic reactions occur more often with which type of local anesthetic?

ester-type Signup and view all the answers

Ester-type anesthetics (procaine) occasionally cause ___ and are inactivated by esterases in the blood.

allergic reactions Signup and view all the answers

Ester-type anesthetics are inactivated by ___ in the blood.

esterases Signup and view all the answers

Amide-type anesthetics (lidocaine) rarely cause ___ and are inactivated by enzymes in the liver.

allergic reactions Signup and view all the answers

Amide-type anesthetics are inactivated by ___ in the liver.

enzymes Signup and view all the answers

Absorbed local anesthetics can ___ excitability in the myocardium and conducting system.

suppress Signup and view all the answers

What are four signs and symptoms of the effect of local anesthetics on the heart?

(1) bradycardia (2) heart block (3) reduced contractile force (4) cardiac arrest Signup and view all the answers

What is a sign of the effect of local anesthetics on the blood vessels?

hypotension Signup and view all the answers

Can local anesthetics cross the placenta?

True Signup and view all the answers

Local anesthetics ___ labor.

prolong Signup and view all the answers

What was the first local anesthetic?

cocaine Signup and view all the answers

Cocaine is a ___-type anesthetic.

ester Signup and view all the answers

What are the three most common surface anesthetics?

(1) lidocaine (2) tetracaine (3) cocaine Signup and view all the answers

What are four methods for patients to minimize the amount of topical anesthetics absorbed and minimize risks?

(1) apply the smallest amount needed (2) avoid application to large areas (3) avoid application to broken or irritated skin (4) avoid strenuous exercise, wrapping the site, and heating the site Signup and view all the answers

Which type of neurons are blocked more rapidly by local anesthetics?

Small, nonmyelinated neurons are blocked more rapidly than large, myelinated neurons. Signup and view all the answers

Termination of local anesthesia is determined in large part by regional ___.

blood flow Signup and view all the answers

What are the main concerns with systemic toxicity of local anesthetics?

(1) cardiac dysrhythmias (2) CNS effects Signup and view all the answers

What are some CNS effects of systemic toxicity of local anesthetics?

(1) seizures (2) unconsciousness (3) coma Signup and view all the answers

What are some ways to reduce the risk of systemic toxicity of local anesthetics?

(1) using the smallest amount needed (2) avoiding application to large areas (3) avoiding application to broken or irritated skin (4) avoiding strenuous exercise and use of dressings or heating pads Signup and view all the answers

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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Description

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.