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17 Cards in this Set
- Front
- Back
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CLASSIFICATION OF LA
Name local anesthetics which are ESTERS |
Cocaine
Procaine Tetracaine Benzocaine |
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CLASSIFICATION OF LA
Name local anesthetics which are AMIDES |
Lidocaine
Bupivocaine Etidocaine Prilocaine |
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ROLE OF LOCAL pH
1.Most Local anesthetics are what in terms of pH? 2.At physiologic pH _ form prevails, _ form is required to penetrate membrane 3. Receptor site is _ to cell membrane 4. _ form is active at the receptor site - protonation occurs _ |
WEAK BASES (pKa = 8-9)
2. Cationic, neutral 3. Internal 4. Ionic - intracellularly |
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Infection causes _ pH which causes less local anesthetics which are neutral to penetrate membrane (may require injection more proximally)
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Low extracellular
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SYSTEMIC ABSORPTION
1. What happens to blood flow when epinephrine is co-administered with LA? What happens to systemic absorption of anesthetic from depot site 2. Local neuronal uptake is enhanced by _ 3. Which drug is exception to this? 4. _ and _ also less dependent on vasoconstriction |
1. Local blood flow DECREASES - systemic absorption DECREASES
2. Higher concentration of the drug 3. COCAINE - NE uptake inhibition 4. Bupivocaine and Tetracaine |
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SPINAL ANESTHESIA
1. Epi produces _ mediated inhibition of release of _ - this _ sensory nerve firing and produces analgesia 2. Epi - _ systemic absorption, _ neuronal uptake and _ alpha 2 activity prolongs local anesthetic effect by 50% |
1. Alpha 2 mediated - Substance P - decreases
2.Decreased, Increased, Increased |
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SURFACE ACTIVITY - ability to reach superficial nerves when applied to skin or mucous membranes
1. Which drugs can do that? 2. EMLA (eutectic mixture of LA) can also do that - what does it include? 3. When is this used? |
1. Cocaine and Benzocaine
2. Lidocaine and prilocaine combination applied as cream or patch 3. For vennipuncture, arterial cannulation, lumbar puncture, dental procedures and in children who dread injections |
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METABOLISM AND EXCRETION
1. Ester type local anesthetics are hydrolyzed in blood by _ 2. Amide local anesthetics are metabolized in _ 3. Metabolites are _ and excreted in _ |
1. Butyrylcholinesterase (tetracaine (long acting), procaine short acting)
2. Liver (prilocaine fastest, bupivocaine slowest) - IMPAIRED LIVER or LIVER DISEASE might result in toxicity by amide drug 3. POLAR - URINE |
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MECHANISM OF ACTION OF LA
1. Blockade of _ channels - prevents _ 2. Access to receptor site gained from _ 3. Receptor affinity is _ or _ dependent |
1. Voltage dependent Na channels - depolarization and conduction of AP
2. Cytoplasm or membrane 3. Voltage or use |
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ACTION OF LA ON NERVES
1. Susceptibility according to nerve diameter - In a nerve root _ fibers are blocked first. Small type _ fibers are blocked next 2. Susceptibility according to myelination - _ fibers tend to be blocked more readily 3. Susceptibility according to location of nerve fiber in bundle - fibers in _ blocked sooner than those _, exposed earlier to higher concentration of anesthetic |
1. Smaller B and C fibers firtst, A delta next (pain fibers first, motor function next)
2. Myelinated fibers are blocked more readily than unmyelinated fibers of the same diameter 3. Periphery sooner than in core |
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Name clinical applications of LA
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- Surface (topical ) anesthesia
- Minor surgical procedures - infiltration, nerve block - Spinal anesthesia - into CSF - Epidural anesthesia - into epidural space |
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Which condition antagonizes effects of LA? What is the mechanism of that?
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HYPERCALCEMIA - antagonizes effects of LA's - shuts down Na channels, increased surface potential favors resting state
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Which condition enhances action of LA's ? What is the mechanism?
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HYPERKALEMIA - extracellular K depolarizes membrane and favors open states (more Na channels open)
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Describe CNS effects (toxicities ) of local anesthetics
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MOST IMPORTANT - most serious are seizures/convulsions followed by coma with respiratory and CV depression
Lower levels- nystagmus, light headedness, restlessness |
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Except _ all local anesthetics are vasodilators
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COCAINE
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Cocaine as drug of abuse causes what CV effects?
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Severe hypertension with cerebral hemorrhage, cardiac arrhythmia and MI
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Prilocaine metabolite causes what (toxicity) ?
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Methemoglobinemia (oxidized Hb - anemia)
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