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Local anesthetics

Local anesthetics. DR.SOBAN SADIQ. Esters Cocaine Benzocaine Procaine Tetracaine Chloroprocaine. Am”i”des Bup i vacaine L i docaine Rop i vacaine Et i docaine Mep i vacaine. Classification. Mechanism of action.

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Local anesthetics

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  1. Local anesthetics DR.SOBAN SADIQ

  2. Esters Cocaine Benzocaine Procaine Tetracaine Chloroprocaine Am”i”des Bupivacaine Lidocaine Ropivacaine Etidocaine Mepivacaine Classification

  3. Mechanism of action • Block voltage gated sodium (Na+) channels in the axonal membrane preventing influx of Na which is required for neuronal conduction • Local anesthetics bind directly to the intracellular voltage-dependent sodium channels

  4. Limit influx of sodium, thereby limiting propagation of the action potential.

  5. Clinical uses • 1-Topical local anesthesia is used for eye,ear,nose and throat procedures • Use drug that is capable of rapid penetration across skin or mucosa with limited tendency to diffuse away from site of application • Cocaine has excellent penetration and local vasoconstrictor effect but its short acting and irritating.

  6. Anesthesia of mucous membranes of the nose, mouth, throat, tracheobronchial tree, esophagus, and genitourinary tract can be produced by direct application of aqueous solutions of salts of many local anesthetics

  7. Infiltration anesthesia is the injection of local anesthetic directly into tissue without taking into consideration the course of cutaneous nerves. Infiltration anesthesia can be so superficial as to include only the skin. It also can include deeper structures, including intra-abdominal organs, when these too are infiltrated

  8. Nerve Block AnesthesiaBrachial plexus blocks are particularly useful for procedures on the upper extremity and shoulder. Intercostal nerve blocks are effective for anesthesia and relaxation of the anterior abdominal wall.

  9. Spinal AnesthesiaSpinal anesthesia follows the injection of local anesthetic into the cerebrospinal fluid (CSF) in the lumbar space.

  10. Toxicity 1-CNS(IMPORTANT TOXIC EFFECTS ARE IN CNS) Low doses: Sleepiness, Light headedness, visual and auditory disturbances, restlessness, tongue numbness.- Higher doses:Nystagmus, Muscular twitching, convulsions, CNS depression.

  11. 2-Peripheral nervous system(Neurotoxicity) • sensory and motor deficits following spinal anesthesia

  12. 3-Cardiovascular System • Block cardiac sodium channels • Depress abnormal cardiac pacemaker activity, Excitability and conduction. • At very high concentration Also block Ca++ channel. Depress strength of cardiac contraction Bupivacaine is most cardio-toxic

  13. Cocaine • vasoconstriction -------------Hypertension • Vasoconstriction ------ ischemia, ulceration of mucous membrane • In chronic users (addictors,snuffers)------- Damage to nasal septum

  14. 4-Blood • Prilocaine (large doses > 10 mg/kg) during regional anesthesia-------- accumulation of metabolite , 0 – toluidine ----------- • convert hemoglobin to methemoglobin • Patient may appear Cyanotic • Methemoglobinaemia can cause decompensation in patients with cardiac or pulmonary disease

  15. 5-Allergic reaction • Ester type : metabolized to p – amino benzoic acid derivatives ------ allergy • Amide type : do not metabolized to PABA

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