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9 Cards in this Set
- Front
- Back
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The "Ideal" Local Anesthetic
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-suitable pharmacokinetics
-adequate potency -safe -non-allergenic -adjuncts not necessary |
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Esters
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Prototype: procaine (NOVOCAIN)
-inactivated, detoxified by plasma esterases; prodcuts of this rxn cause *allergies Others: cocaine (the only vasoconstrictor), benzocaine (topical) |
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Amides
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Prototype: lidocaine (XYLOCAINE)
-most widely used -hepatic metabolism produces inactive metabolites |
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Local Anesthetic Mechanism
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-uncharged form crosses into neuron
-inside, must re-equilibrate to active protonated form -active form binds Na channels in their inactive state, decreasing depolarization (no effect on resting nerve) |
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LA Affected Tissues
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-all if dose sufficiently high
-neuronal susceptibility: small>large, nonmyelinated>myelinated, rapid firing>slow>resting -order of sensory loss: pain (small), temp, touch, deep pressure -sensation restored in reverse order |
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LA Metabolism
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Unmetabolized = active form.
Slow metabolism means faster onset, longer duration, greater apparent potency; but also higher toxicity |
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LA in ischemic tissue
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Ischemic tissue has lower pH, causing less diffusion of LA into neurons.
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LA toxicity
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-CV depression: vasodilating effect; LAs rarely used as anti-arrhythmic
-Medullary/ventilatory depression -CNS stimulation: apnea during seizures is main cause of death |
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Allergenicity of LAs
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-variable incidence and severity
-esters>amides -cross-reactivity within class -allergy can be to paraben preservatives |
