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Chapter 26

Local Anesthetics

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Local Anesthetics

Suppress pain by blocking sodium channels, thereby blocking impulse conduction along axons

Only in neurons located near the site of administration

Suppress pain without generalized depression of nervous system

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Local Anesthetics

Basic pharmacology of local anesthetics Properties of individual local anesthetics Clinical use of anesthetics

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Basic Pharmacology of Local Anesthetics

Classification Esters Amides

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Fig. 26–1. Structural formulas of representative local anesthetics.

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Basic Pharmacology of Local Anesthetics

Mechanism of action Suppress pain by blocking sodium channels,

thereby blocking impulse conduction along axons

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Basic Pharmacology of Local Anesthetics

Selectivity of anesthetic effects Only in neurons located near the site of

administration Suppress pain without generalized depression of

nervous system

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Time Course of Local Anesthesia

Onset of local anesthesia Termination of local anesthesia

Impact of regional blood flow

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Basic Pharmacology of Local Anesthetics

Use with vasoconstrictors Prolong anesthesia Reduce the risk for toxicity—slow absorption

Fate in the body Absorption Distribution Metabolism

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Basic Pharmacology of Local Anesthetics

Adverse effects CNS Cardiovascular Allergic reaction Labor and delivery

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Properties of Individual Local Anesthetics

Procaine Lidocaine Cocaine Other local anesthetics

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Procaine

Was formerly the anesthetic of choice for injection

Now replaced by others Preparations

Available in solution (1%, 2%, and 10%)

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Lidocaine

Most widely used local anesthetic Topical and injectable applications Effects extended if given with epinephrine Also used for cardiac dysrhythmias

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Lidocaine

Preparations Cream Ointment Jelly Solution Aerosol Patch

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Cocaine

First local anesthetic Central nervous system (CNS) effects Peripheral nervous system (PNS) effects

(sympathetic) Cardiovascular effects Preparation and administration Should not be given with vasoconstrictor

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Other Local Anesthetics

Grouped according to route Topical Injection

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Other Local Anesthetics

Topical Therapeutic uses Systemic toxicity

Injection Infiltration, nerve block, IV regional, epidural, and

spinal (subarachnoid) Should be administered by anesthesiologist IV and monitoring required