local anesthetics

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Pharmacology of Local anesthetics

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Local anesthetics Albert Niemann, Carl Koller, Sigmund Freud Cocaine Na+ channel blockers Reversible inhibition of generation & conduction of nerve impulse Sensory & motor paralysis in the innervated area Molecular size determine receptor binding

classification:

classification Amides: lidocaine, bupivacaine, ropivacaine Esters :cocaine, procaine, amethocaine Others; dyclonine, pramoxine. Short acting: <20min. cocaine, procaine Intermediate:60-120min. lidocaine, articaine Long acting: >120min.ropivacaine, bupivacaine, etidocaine

Mechanism of action:

Mechanism of action Amino acid residues in channel protein important for LA binding Receptor found within the intracellular half of the pore of Na+ channel Action: frequency and voltage dependent nerve diameter dependent Differential sensitivity of nerve fiber Pain, temperature, touch, deep pressure finally motor function

MOA………….. CONTD:

MOA………….. CONTD Alkaline PH increases action Membrane penetration poor in acidic PH Physically plugging of channel pore. Exert variety of non-specific effect on membrane Resting nerve less sensitive At higher concentration block K+ & Ca++ channels

LA ..Dynamics:

LA ..Dynamics Vasoconstrictors potentiate action LA + adrenaline contraindicated in major cardiac diseases, end artery tissues CNS stimulation clonic convulsions Myocardial excitability, automaticity, contractility decrease Spinal anesthetics depress skeletal muscle contractions

Clinical types:

Clinical types Topical/surface anesthesia Infiltration anesthesia Field block Nerve block- brachial, cervical plexus & intercostal ; sciatic & femoral nerve nerve lock Spinal Epidural Intravenous regional anesthesia

Other uses:

Other uses Intractable cough Cancer pain Mouth ulcers Soft tissue rheumatism Muscle spasticity Cardiac arrhythmias Post-herpetic neuralgia

Interactions:

Interactions Procaine+ succinylcholine-potentiation Procaine+sulphonamides –antagonism Procaine+penicillin-insoluble complex +adrenaline/felypressin;

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