Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
79 Cards in this Set
- Front
- Back
LAs reversibly block the _____ and _____ of nerve impulses
|
generation and propagation
|
|
bi-directional blockade
|
LAs can alter both sensory and motor function because LAs can block function in ALL excitable cells
|
|
LAs used to decrease what?
|
1) pain
2) temp 3) touch perception 4) skeletal muscle tone |
|
level of effect depends on what?
|
1) agent used
2) route of administration 3) drug concentration at site 4) lipophilicity |
|
route of LAs
|
1) topical (skin, MM)
2) parentetral (peripheral, cnetral, spinal) 3) rectal 4) ophthalmical |
|
many of LAs also used as:
|
antiarrhythmics
|
|
What control the compounds ability to penetrate the nerve sheath and enter the nerve membrane?
|
the lipophilicity of the aromatic group
|
|
most of LAs are:
|
ionizable weak bases
|
|
ionizable weak bases can exist as:
|
1) the freebase or
2) the positively charged form which will alter their action at the site |
|
all agents act to decrease:
|
the permeability of the membrane to sodium ions
|
|
LAs bind to sites in the:
|
Na channel of the voltage gated Na channels (inhibit Na inflow during depolarization)
|
|
low concentration of LAs decreases:
|
both 1) the rate of rise and
2) the height of the action potential (higher conc. can abolish it totally) |
|
LAs increase:
|
1) firing threshold
2) total propagation time |
|
in myelinated fibers, this occurs only at the:
|
Nodes of Ranvier
|
|
K outflow
|
may also be inhibited somewhat, but not nearly to the extent of Na
|
|
most of LAs act by binding to:
|
inner portion of Na channel
|
|
Which nerves are affected first?
|
1)small diameter nerves
2) more rapidly stimulated fibers 3) autonomic fibers |
|
Why are small diameter nerves affected first?
|
small diameter nerves are affected first, then larger diameter nerves due to the # of channels to be blocked (greater in large fibers)
|
|
Why are more rapidly stimulated fibers blocked first?
|
due to 1) more frequent opening of Na channels and
2) the ability of the LAs to get into channel to bind |
|
the order of fibers get affected
|
1st: autonomic fibers
2nd: sensory 3rd: motor |
|
selsective Na channel blockers
|
1) tetrodotoxin
2) saxitoxin |
|
tetrodotoxin
|
from pufferfish
|
|
saxitoxin
|
from red tide microorganisms (paralytic shellfish poisoning)
|
|
Where selective Na channel blockers block?
|
OUTER mouth of Na channel
|
|
LAs use as antiarrhythmic agents is due to the:
|
1) blockade of Na channels in myocardial tissues
2) effective decrease in firing rate 3) effective decrease in passage of signals through conductive fibers |
|
topical
|
decrease pain of wound, burn, MMs
|
|
infiltration
|
injected around area (ie. for Sx)
|
|
regional nerve block
|
injected close to nerve that innervates the area to be anesthetized
|
|
spinal
|
injected into lumbar subarachnoid space to get to nerves in that area going to various body sites)
|
|
epidural
|
given under the dura mater - keeps agent from rising higher up spinal column)
|
|
intravenous
|
usually for Sx on a specific limb
|
|
selection of LAs minly based on its:
|
pharmacokinetics
|
|
fast onset
|
1) lidocaine
2) prilocaine |
|
slow onset
|
1) procaine
2) tetracaine |
|
short duration (15-30 min.)
|
1) procaine
2) chloroprocaine |
|
intermediate duration (30-90 min.)
|
1) lidocaine
2) prilocaine |
|
long duration (2-3 hrs)
|
tetracaine
|
|
epi.
|
may be used to increase duration, but is not always effective
|
|
onset on MMs
|
fastest onset: benzocaine
2nd: lidocaine and cocaine (topical duration: 30-60 min.) |
|
local hypersensitivity more commone with:
|
ester type
|
|
examples of preps which increase sensitivity risk:
|
1) tartrazine
2) sulfites |
|
systemic absorption can lead to:
|
1) cardiotoxic risk
2) potential CNS symptoms (sedation, dizziness, disorientation, tremors, seizures, resp. arrest) |
|
the LAs are classified by:
|
their structure
1) ester 2) amide 3) neither |
|
esters
|
1) benzocaine (oragel)
2) procaine (novocaine) 3) chloroprocaine (nesacaine) 4) tetracaine (pontocaine) 5) cocaine 6) cetacaine (cetylite) |
|
amides
|
1) lidocaine (xylocaine)
2) prilocaine (citanest) 3) mepivacaine (carbocaine) 4) bupivacaine (marcaine) 5) articaine (septocaine) 6) ropivacaine (naropin) |
|
not true amides or esters
|
pramoxine (proctofoam)
|
|
esters are hydrolyzed by:
|
cholinesterases
|
|
1) Benzocaine (Oragel)
|
1) poorly water soluble
2) topical use only 3) pKa ~3.5 |
|
excessive absorption of Benzocaine may lead to:
|
methemoglobinemia
|
|
2) Procaine (Novocaine)
|
1) 1st synthetic local anesthetic
2) slower onset with short duration 3) weak potency 4) fairly low systemic toxicity 5) use superceded by better agents (amides) |
|
Procaine is best for:
|
infiltration and nerve block
|
|
3) Chloroprocaine (Nesacaine)
|
1) ester
2) rapid onset, short duration 3) low syst. toxicity 4) used in high [ ] 5) for infiltration, nerve block, IV, and epidural use |
|
4) Tetracaine (Pontocaine)
|
1) ester
2) long duration with slow onset 3) spinal (major use) 4) topical (absorption across MMs limit its use) |
|
potency of Tetracaine
|
10 times more potent than procaine, but also 10 times more toxic
|
|
Why Tetracaine used in spinal anesthesia?
|
because the barriers decrease diffusion and decrease toxicity risk
|
|
5) Cocaine
|
1) ester
2) C-2 controlled substance 3) only use in topical on MMs(too toxic for other uses) |
|
uniquness of Cocaine
|
1) potent vasoconstrictive activity
2) addiction liability in addition to it's LA effect |
|
6) Cetacaine (Cetylite)
|
1) ester
2) topical for local skin disorders (not for MMs) 3) for opthalmology |
|
Cetacaine is a mixture of:
|
1) Benzocaine
2) Tetracaine 3) Butyl Aminobenzoate |
|
use of Cetacaine
|
1) topically
2) rectally 3) spray to inhibit the gag reflex (during bronc. exam) |
|
amides are metabolized mainly in the:
|
liver
|
|
1) Lidocaine (Xylocaine)
|
1) amide
2) most commonly used LA 3) rapid onset with intermediate duration 4) used for most types of applications |
|
Why many formulations of Lidocaine include Epi?
|
because Lidocaine causes vasodilation
|
|
2) Prilocaine (Citanest)
|
1) amide
2) similar to lidocaine in properties, but LESS vasodilation 3) rapid onset, intermediate duration |
|
toxicity of Prilocaine
|
least toxic of the amides, but can still cause methemoglobinemia
|
|
3) Mepivacaine (Carbocaine)
|
1) amide
2) similar to lidocaine 3) used for infiltration, nerve blocks, epidural 4) not effectively topically |
|
Why Mepivacaine is not used in obstetrics?
|
because biotransformation in fetus is prolonged
|
|
4) Bupivacaine (Marcaine)
|
1) amide
2) long duration, with slower onset 3) high potency 4) used for infiltration nerve block, epidural, and spinal |
|
Is Bupivacaine more toxic than Lidocaine?
|
Yes! (cardiotoxic)
|
|
5) Articaine (Septocaine)
|
1) amide
2) only available in US in combination with Epi 3) similar to lidocaine 4) short duration and rapid onset |
|
use of Articaine
|
used for dental and peridontal procedures
|
|
toxicity of Articaine
|
low systemic toxicity due to rapid breakdown (it has an ester group in addition to an amide)
|
|
6) Ropivacaine (Naropin)
|
1) amide
2) long duration 3) similar to Bupivacaine, but less cardiotoxic 4) less lipid soluble, and more rapidly metabolized than Bupivacaine |
|
use of Ropivacaine
|
similar to Bupivacaine
1) infiltration 2) nerve block 3) epidural 4) spinal |
|
Bupivacaine and Ropivacaine
|
1) Bupivacaine: R-isomer
2) Ropivacaine: S-isomer |
|
Pramoxine (Proctofoam)
|
1) not true amide or ester
2) topical agent for relief of hemorrhoids, rectal pain and itching of skin disorders (pruritis) |
|
potency of Pramoxine
|
weak potency (will not totally abolish gag reflex)
|
|
Pramoxin mixed in combination with many products such as:
|
1) hydrocortisone
2) calamine |
|
liposomal formulation
|
Liposomes are somewhat like cells in that they are round shells of phospholipids, the basic components of human cell walls. Enclosing a drug within a liposome entraps the drug as ‘payload,’ protecting it from early degradation within the body. Liposome encapsulation also improves a medication’s bioavailability (the amount of time and specific distribution within the body), which can extend the treatment effect and reduce dosing.
|