Term
| T/F. ALL local anesthetics are bases |
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Definition
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Term
| Do local anesthetics have the ability to block Na+ channels in cardiac tissue? |
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Definition
| Yes, lidocaine is used as an antiarrhythmic for this reason |
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Term
| T/F. A local anesthetic with a pKa of 8.4 will always have a faster onset than one with a pKa of 8.6. |
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Definition
| FALSE. The lipid solubility of the non-charged species must be taken into account. If the non-charged lipid solubility of the LA with a pKa of 8.6 is higher than the one with a pKa of 8.4 it will cross membranes faster |
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Term
| T/F. Local anesthetics (LA's) are ligand-gated sodium channel blockers. |
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Definition
| FALSE. They are voltage-gated |
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Term
| What are the 3 components that a local anesthetic molecule is made of? |
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Definition
1. aromatic ring (lipophilic)
2. intermediate side chain (ester or amide)
3. terminal amine (either tertiary or quarternary) |
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Term
| What is the relevance of the terminal amine of a local anesthetic? |
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Definition
| They are either tertiary amines or quarternary amines. If the terminal amine is tertiary it will be lipid soluble and cross membranes well. If it is quarternary it will be charged rendering it water soluble and will not cross membranes. |
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Term
| Do LA's affect myelinated or unmyelinated nerves first and why? |
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Definition
| unmyelinated, because myelinated axons have much more material to go through (oligodendrocytes in CNS and Schwann cells in PNS). |
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Term
| Do LA's affect smaller or larger diameter axons first? |
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Definition
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Term
| This LA is a diamine that will have two pKa's and two charges making it very water soluble. |
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Definition
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Term
| since procaine has two amines and thus two pKa's which one matters the most? |
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Definition
| The higher pKa because it will be the one hardest to change over |
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Term
| If carbonyl carbon next to nitrogen it is an _________. If it is next to an oxygen it is an _________. |
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Definition
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Term
| which drug would be better for someone with liver disease, lidocaine or tetracaine? |
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Definition
| tetracaine because it is an ester and does not rely on the liver for metabolism |
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Term
| T/F. Increasing lipid soluble increases onset time. |
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Definition
| FALSE. It decreases onset time (works faster) |
|
|
Term
| How does increasing lipid solubility of LA's affect duration? |
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Definition
| The more lipid soluble, the more that gets inside the cell. Once it is inside the cell it will become ionized so it is soluble in cellular fluid. Now that it is mostly ionized, it is harder to cross the cell membrane to get OUT and undergo metabolism |
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Term
| T/F. Neurons that are more frequently stimulated are more rapidly affected by LA's |
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Definition
|
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Term
| Do LA's alter resting membrane potential or threshold potential? |
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Definition
|
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Term
| which subunit of the sodium channel contains the sodium pore? |
|
Definition
|
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Term
| Local anesthetic molecules can gain access to receptors ONLY when sodium channels are in __________ states. |
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Definition
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Term
| Which fibers are usually blocked first, sensory or motor fibers? |
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Definition
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Term
| T/F. Recovery from LA blockade is in the reverse order from which the fibers were blocked |
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Definition
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Term
A) Which LA's have the fastest onset time?
B) Which have the shortes DOA? |
|
Definition
A) lidocaine and prilocaine
B) procaine and chloroprocaine |
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|
Term
Which LA has the fastest onset time when applied topically?
How long do most agents last if applied topically? |
|
Definition
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|
Term
A) Local hypersensitivity reactions are more common with _______ type anesthetics.
B) _______ are in LA's that contain vasopressors and pose a risk of hypersensitivity. |
|
Definition
A) Ester
B) metabisulfites |
|
|
Term
| In what anesthetics is methemoglobinemia most often seen? |
|
Definition
| Topical anesthetics- prilocaine, benzocaine, lidocaine, cetacaine |
|
|
Term
| Amides are metabolized by _________ and esters are metabolized by _________. |
|
Definition
| P45) enzymes in liver; plasma and other esterases |
|
|
Term
|
Definition
> Poorly water soluble so used topically
> very severe in causing methemoglobinemia
> pKa 3.5 |
|
|
Term
|
Definition
> slow onset and short duration
> weak potency
> fairly low systemic toxicity
> best for infiltration and nerve block
> Not used much anymore b/c there are better agents (amides) |
|
|
Term
| Why is benzocaine not used parenterally? |
|
Definition
| Because it can easily cause methemoglobinemia |
|
|
Term
| choloroprocaine (Nesacaine) |
|
Definition
> Rapid onset and short duration
> Low systemic toxicity
> used in high conc. solutions since toxicity is low
> best for infiltration, nerve block, and epidurals |
|
|
Term
|
Definition
> 10x potency (& toxicity) of procaine
> slow onset and long duration
> Typically used only for spinals where the barriers decrease diffusion and toxicity risk |
|
|
Term
|
Definition
> C-II controlled substance derived from the leaves of the coca plant
> too toxic for uses other than topical
> potent vasoconstrictive activity
> used topically on mucous membreanes prior to surgery and packed post-op to decrease bleeding and pain |
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|
Term
|
Definition
> Used topically (except eye), rectally, or as a spray to inhibit gag reflex
> mixture of benzocaine, tetracaine, and butyl aminobenzoate |
|
|
Term
|
Definition
> most commonly used LA
> rapid onset w/ intermed. duration
> causes vasodilation so many formulations include epinephrine
> Useful for most applications |
|
|
Term
|
Definition
> similar to lidocaine in properties, but less vasodilation
> rapid onset, intermed. duration
> least toxic of amides, but can still cause methemoglobinemia |
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|
Term
|
Definition
> uses similar to lidocaine
> used for infiltration, nerve block, & epidural
> Not effective topically
> Not used in O.B. b/c biotransformation in fetus is prolonged
> racemic mixture (equal amounts of D and L enantiomers)
> structurally similar to bupivacaine and ropivacaine |
|
|
Term
|
Definition
> slow onset, long duration
> very potent
> more toxic than lidocaine (cardiotoxic)
> used for infiltration, nerve block, epidural and spinal anesthesia |
|
|
Term
| Which LA is most likely to cause adverse effects? |
|
Definition
|
|
Term
|
Definition
> only available in combo w/ epi
> similar to lidocaine- rapid onset, short duration
> used for dental/periodontal procedures
> Low systemic toxicity due to rapid breakdown
> Has an ester group and an amide- however classified as an amide |
|
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Term
|
Definition
> long duration
> similar to bupivacaine, but less cardiotoxicity
> is an S-isomer whereas bupivacaine is racemic (the R-isomer is cardiotoxic)
> less lipid soluble and more rapidly metabolized than bupivacaine
> used for infiltration, nerve block, epidural, and spinal |
|
|
Term
|
Definition
> not an ester or amide
> topically used for relief of hemorrhoids, rectal pain, and itching of skin disorders
> weak potency
> mixed in combo with many products such as hydrocortisone, calamine |
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