Local Anesthetics Win-2020 post.pptx - Integrated Medicinal Chemistry and Pharmacology II PSC 6311 Local Anesthetic Agents Katzung Basic and Clinical

Local Anesthetics Win-2020 post.pptx - Integrated Medicinal...

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Local Anesthetic Agents Integrated Medicinal Chemistry and Pharmacology II PSC 6311 Karen S. Mark , Ph.D. ; Associate Professor Pharmaceutical Sciences Office: Room 275 email: [email protected] ph: 865-288-5839 Katzung, Basic and Clinical Pharmacology , 14 th ed.; Chapter 26 Foye’s, Principles of Medicinal Chemistry , 8 th ed.; Chapter 12 Foye’s, Principles of Medicinal Chemistry , 7 th ed.; Chapter 16 Goodman & Gilman’s The Pharmacological Basis of Therapeutics , 13 th ed.; Chapter 22
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Lecture Objectives 1.Identify which nerves transmit pain sensation 2.Describe the chemical classes of local anesthetics and the mechanism of action3.List signs and symptoms of local anesthetic side effects and toxicity 4.Describe the reason(s) for adding epinephrine to local anesthetic therapy5.Explain the impact of injecting a local anesthetic agent into an abscess/wound 6.Explain the properties that determine potency, onset and duration of action
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Local Anesthetic Drugs Covered in this Section Ester-type Benzocaine Cocaine Procaine Tetracaine Amide-type Articaine Bupivacaine Lidocaine Mepivicaine Prilocaine Ropivacaine
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Introduction Local anesthetics block initiation & conduction of APs on nerves causing sensory & motor paralysis in localized area Advantages Reversible action at clinical conc. Complete recovery in nerve fxn Requires minimal equipment Minimal systemic effects Effective anesthesia to nerve region Reduces need (or amt) for opioids to control pain Disadvantages Requires compliant patient May require use of sedation Possible systemic effects
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Pain Nerve Transmission
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Nerve Classification Note : C and Aδ fibers are responsible for conducting pain; thus, targets for analgesia/ sedation/ and anesthesia C fibers (smallest) transmit the slow burning pain, unmylenated A δ fibers transmit the fast pain signals, smallest, mylenated Aδ are thinnest
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Fiber Classifi- cation Anatomic Myelin Diameter (μm) Conduction velocity (m/sec) Function Sensitivity to block A fibers A-alpha ( a ) Afferent to / efferent from muscles & joints Yes 6-22 10-85 Motor & proprioception + A-beta ( b ) Yes ++ A-gamma ( g ) Efferent to muscle spindles Yes 3-6 15-35 Muscle tone ++ A-Delta ( d ) Sensory roots; afferent peripheral nerves Yes 1-4 5-25 Pain, temperature, touch +++ B fibers Preganglionic sympathetic Yes <3 3-15 Vasomotor, visceromotor, sudomotor, pilomotor ++++ C fibers Postganglionic sympathetic No 0.3-1.3 0.7-1.3 Vasomotor, visceromotor, sudomotor, pilomotor ++++ Sensory dorsal root; afferent peripheral nerves No 0.4-1.2 0.1-2 Pain, temperature, touch ++++
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Clinical Uses – Local Anesthetics Topical anesthesia cornea (opthalmologist), mouth Infiltration anesthesia minor surgery (e.g. dental practice, tissue biopsy) Field block, nerve block anesthesia Spinal and epidural anaesthesia blockade of pain via spinal nerves during labor or as part of major surgery
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Typical Injection Sites for Spinal Anesthesia Using Local Anesthetic Agents
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Na + Channel Subunit / Blockade Puffer fish Clams & Mussels Dart frog natural teratotoxins bind at external site local anesthetics bind at internal site
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Local Anesthetic Drugs - MOA
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