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13 Cards in this Set
- Front
- Back
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1. Describe the characteristics of an ideal local anesthetic.
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a. Stable in formulation
b. Effective for TOPICAL application or LOCAL injection c. RAPID ONSET w/ good DOA (generally short) d. REVERSIBLE blockade of sensory nerve fibers e. Low systemic absorption and toxicity (i.e., it’s a local anesthetic) f. No DAMAGE/ IRRITATION of tissue. |
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2. Describe the currently accepted mechanism of action for local anesthetics.
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a. Temporary loss of nerve transmission by blocking sodium channels
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3. Explain why a vasoconstrictor like epinephrine might be co-administered with a local-anesthetic.
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a. Attempts are made to reduce blood flow in the area of injection via co-administration of epinephrine (vasoconstrictor) to improve duration of action.
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4. Describe the types of toxicities that might be observed with local anesthetics.
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a. Related to actions on other excitable membranes:
1. Na+ and K+ channels in the heart 2. Nerve cells in the CNS 3. Nicotinic acetylcholine receptors in the NMJ b. Affects on the heart can include arrhythmia or cardiac arrest. c. CNS affects can lead to convulsions (inhibition of GABA systems?). d. Methemoglobinemia with prilocaine. |
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5. Describe the general structural requirements for local anesthetics.
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a. Generally—An aryl group, alkyl bridge with sp2 hybridized carbon & ionizable amine.
b. Increased lipophilicity increases potency. c. pKa = 7.5 – 9.5 1. Higher is too ionized 2. Lower is not ionized enough d. 3o alkylamine best |
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5. Describe the general structural requirements for local anesthetics
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a. Generally—An aryl group, alkyl bridge with sp2 hybridized carbon & ionizable amine.
b. Increased lipophilicity increases potency. c. pKa = 7.5 – 9.5 1. Higher is too ionized 2. Lower is not ionized enough d. 3o alkylamine best |
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6. Explain why it is especially important to have an ionizable nitrogen atom for local anesthetics that are administered by injection.
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a. Hydrophilicity needed to prepare dose for injection
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7. Explain why it is important that local anesthetics have some degree of lipophilic character.
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a. to cross the multiple hydrophobic membranes protecting the neuron.
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8. Describe a drug interaction that may occur with procaine and sulfonamide antibiotics.
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a. Formation of PABA (result of procaine hydrolysis) can lead to a drug interaction between procaine and sulfonamide antibiotics.
b. Sulfonamide antibiotics prevent PABA from incorporating into folic acid. Therefore, production of PABA by procaine hydrolysis can negate the sulfonamide effect. |
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9. Explain why benzoic acid derivatives have a shorter duration of action compared to p-aminobenzoic acid derivatives.
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Due to resonancePABA derivatives have:
a. Increased stability but still susceptible to hydrolysis b. Increased activity However, PABA also results in: c. Allergic reactions d. Sulfonamide interaction |
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10. Explain why local anesthetics that are amino esters (PROCAINE) are short acting compared to local anesthetics that are amino amide derivatives (LIDOCAINE).
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for AMINO AMIDES
a. Resonance effects make them less susceptible to hydrolysis. b. Ortho methyl groups provide protection from hydrolysis via steric hindrance. c. Therefore the major route of metabolism is the liver. |
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11. Describe the effect that ortho-methyl groups in amino amides have on hydrolysis rates.
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a. Reduce them due to steric hindrance
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12. Describe the different metabolic routes for the amino esters compared to the amino amide local anesthetics
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a. Amino Esters
1. Hydrolysis by esterases b. Amino Amides 1. Major metabolic pathway: 1. N-dealkylation (acetaldehyde production) 2. Other steps: 1. Aromatic hydroxylation 2. Conjugation 3. Hydrolysis by amidasesh |
