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98 Cards in this Set

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Which type of nerve fibers are the most sensitive to anesthetics?
-high frequency nerve fibers
-the channels become open more often and the drug has an affinity for the open channels
-higher surface area:volume ratio = more rapid diffusion
-no myelination
-a small amount may enter externally
uses of anesthetics
nerve, ganglion, spinal block
cardiac dysrhythmias
(heart has Na channels)
What are three ester-linked local anesthetics?
cocaine
procaine
tetracaine
What are the three molecular parts of an anesthetic?
aromatic ring (lipophlic)
ester or amide linkage
tertiary amine (hydrophilic)
What are two amide linked local anesthetics?
lidocaine
mepivacaine
How are ester-linked local anesthetics metabolized?
Plasma Colinesterase
How are amide-linked local anesthetics metabolized?
Liver
In terms of the molecular structure of the local anesthetics what does the tertiary amine contribute to?
-hydrophilic
-Determines the ability to move through the axoplasm
In terms of the molecular structure of the local anesthetics what does the aromatic ring contribute to?
-It is the lipophilic portion of the drug.
-Determines two things:
1) Na channel receptor affinity
2) Ease in crossing axonal membrane
Receptor affinity for a local anesthetic is directly proportional to.....?
lipophilicity
Local anesthetic's axoplasmic movement across the membrane is directly propotional to.....?
hydrophilicity
If a drug is net hydrophilic than what are its onsets and how potent is it?
less potent, but faster onset and shorter acting
If a drug is net lipophilic than what are its onsets and potentcies?
highly potent, but slower onset and longer acting
How what happens when an anesthetic binds to a sodium channel?
It raises the threshold for depolarization therefore limiting the electric signal along the axon of a nerve.
How does the anesthetic reach the Na channel receptor?
-A small portion goes to an uncharged form.
-The uncharged form crosses the membrane driven by a concentration gradient
-The uncharged form becomes ionized and binds with the Na channel receptor
How do the pKa of the drug and the pH play a role in anesthetizing?
-pKa determines the proton association
-the higher the pKa the more drug you will need
-association is influenced by the pH
-the lower the pH the more drug you will need
How does infected tissue play a role in local anesthesia?
-infected tissue has a low pH
-vasoconstrinction increases so the drug will be taken away
-need more drug, toxicity increases
What is a special feature of the ester-linked procaine and tetracaine that has to be considered before administration?
They compete with the antibiotic, sulfanilamide, used in treating UTI's.
What is it about the excretion of local anesthetics that has to be considered? How would you deal with this?
-local anesthetics are weak bases
-drugs that have been excreted can be reabsorbed back into the plasma by the collecting tubule
-acidifying the urine (w/ ammonium chloride) will ionize the drug and prevent reabsroption
What 5 factors must you consider in regards to how toxic a drug may be?
1) type of drug and how it is excreted
2) amount administered
3) vascularity of injection site
4) vasoconstrictors - prolongs therapeutic effect (epinephrine on procaine, lidocaine and mepivacaine)
5) rate of injection - greater pressure = larger field
What are the symptoms of CNS toxicity from local anesthetics?
-tinnitus (ringing in the ears)
-euphoria
-confusion
-numbness
-stimulation followed by depression, affects the cerebral cortex and the medulla
What are the symptoms of cardiovascular toxicity from local anesthetics?
-hypertension (initially)
-then myocardial depression because Ca channels may be blocked-->
-hypotension
What are the toxicities from cocaine?
-problem in highly trained athletes
-hypertension
-arrhythmias
-coronary artery spasm
What are some good ways to prevent the toxic effects of local anesthetics?
-premedicate
-smallest dose
-use vasoconstrictor (epinephrine)
-get a history
How would you use local anesthetics for surface anesthesia?
-tetracaine,lidocaine and cocaine (for respiratory)
How would you use local anesthetics for under the skin anesthesia?
lidocaine, procaine, and bupivacaine w/ epinephrine
Where would you place anesthetic for a spinal block?
What does anesthetize?
-L3/L4
-everything inferior to the waist
Where would you place anesthetic for a pudendal nerve block?
What does it anesthetize?
-near the ischial spine by Alcock's canal
-anesthtizes S2-S4 and lower 1/4th of vagina
Where would you place anesthetic for a epidural block?
What does it anesthetize?
-through the sacral hiatus to the epidural space
-anesthetizes S2-S4 nerve fibers, pain fibers from cervix, upper vagina and afferent fibers from the pudendal nerve.
-WILL STILL FEEL CONTRACTIONS!
Salicylates
Aspirin
nociceptive pain
-result of stimulating free nerve ending and peripheral pain receptors
-can be suppressed or enhanced
Two types of nociceptive pain
neospinothalmic tract: sharp, well defined, A-delta fibers, treated with cyclo-oxygenase inhibitors (COX)
paleospinothalmic tract: dull, persistent, less well defined, burning, carried by C-fibers, treated with opioids
neuropathic pain
nervous system dysfunction
-burning or tingling
-tumors, shingles, phantom limb, diabetes
-defect in NMDA receptor function from a glutamate pathway dysfunction
What are the treatments for neuropathic pain?
Antisiezure drugs:
gabapentin
carbamazepine
SNRI's (selective norepinephrine inhibitors)
What are the therapeutic uses of salicylates?
Analgesia,
anti-inflammatory
anti-rheumatoid (arthritis)
antipyretic (fever)
anticoagulant
How do salicylates treat pain?
-they prevent the formation of prostaglandins, which are responsible for maintaining the sensitivity free nerve endings
-block both COX-1 and COX-2
-these produce the prostaglandins from arachidonic acid
COX-2
-induced by inflammatory cells
from the brain and kidney
-maintains kidney circulation
-it would be best just to treat this one
COX-1
-in most tissues
-involved in homeostasis
-platelet aggreagation
How do salicylates have an antirheumatoid effect?
(4 things)
-reduces edema by maintaining capillary wall integrity
-inhibits the release of neutrophils
-stabilizes lysozomes to prevent the release of proteases
-inhibits the formation of free radicals
What are the mechanisms for the salicylates' antipyretic effects?
-COX inhibition in the CNS
-inhibition of interleukin-1 (released from macrophages)
Absorption of salicylates
-low pH in stomach keeps it at a unionized form so it can be absorbed
-mostly in the small intestine where there is a high surface area
What are the mechanisms for the salicylates' anticoagulant effect?s
-decrease in platelet adhesive
-decrease in prothrombin levels
excretion of salicylates
-the acid form will keep it from being reabsorbed in the kidneys
-increasing urine volume prevents reabsorption
-tubular secretion by active transport out of blood to urine
What are the toxicity problems of salicylates?
-GI problems, ulcers, gastritis
-this is from COX-1 inhibition
-also disruption of acid base balance
Phase-1: low level overdose of salicylates
-Uncoupling of OX PHOS
-increased respiration from uncoupling and medulla mechanism
-increased respiration blows off the CO2
-decreases [H2CO3]
-respiratory alkalosis
What are the effects of salicylate overdose?
-increases temp from uncoupling
-metabolic acidosis from lactic acid build up
-renal failure
-cardiovascular: vasodilation
Phase-2: high level overdose of salicylates
-respiratory rate decreases by mechanism on medulla
-CO2 levels are maintainted
-[H2CO3] increases
-respiratory and metabolic acidosis
How would you treat an salicylate overdose?
-charcoal to reduce GI absorption
-give bicarbonate as a buffer
-lower body temp
-fluids for excretion
What are the interaction precautions to worry about with salicylates?
-displaces thyroid hormone and corticosteroids from plasma proteins (heart problems)
-Reye's syndrome in children-> encephalopathy and hepatic injury
Pharmacologic effects of acetaminophen (tylenol)
-Analgesia and antipyresis
-not antiinflammatory or antirheumatic
-only inhibits COX at inflammation sites in the brain
What are the added benefits of acetaminophen compared to salicylates?
-no gastric erosion
-no anticoagulant effect
-no change in acid base
-does not interfere with gout treating agents
-no problem with Reye's syndrome
Side effects or toxicities of acetaminophen
-formation of a toxic intermediate (NAPQI) which can cause cell death
-alcoholics are at risk bc CYP450 is induced
(is this true, not inhibited?)
-overdose has problems bc glutathione cannot remove toxic intermediate
-blood problems (cyanosis)
4 reasons to use opioids
pain relief (dull visceral)
antitussive effects
diarrhea
acute pulmonary edema
What are the origins of opioids?
Phenanthrenes
Benzylisoquinolines
What are the mechanisms of action from opioids?
-receptors in the brain and SC
-bind to sites where endogenous ligands bind
What is it about the morphine that doesn't allow it to be as effective as heroine?
-heroine gets into the brain 2.5 times betters because of its structure.
What are the two endogenous ligands that bind to the opioid receptors?
-leu- and met-enkephalin
-five amino acid sequence found in beta-endorphin, dynorphin and other things
What type of receptor are the opioid receptors?
7-transmembrane g-protein
What it is mechanism of the opioids?
-cAMP induced ---->
-presynaptically preventing pain NTs'
-hyperpolarizes membrane
-blocks calcium transport
chronic effects of opiods
-no long-term pathology
-high pain tolerance, need more for the same amount of pain
-metabolic tolerance, GI becomes better at digesting
Effects of opioids on CNS
-elevates pain threshold
-codeine has a ceiling effect
-euphoria (less so for acute pain)
-miosis (constriction of pupil)
-need laxative
-respiratory depression (deadly)
-lowering of the seizure threshold, especially head injuries
-nausea
-hypothermia
-antitussive
-endocrine - inreases water retension and decreases other things
Effects of opioids on CV
-hypotension
-dilates capillary bed from histamine release
-increases cerebral circulation from vasodilation
-useful in patients with an MI or pulmonary edema (left ventricle failure), lowers workload of heart
Effects of opioids on GI
-spastic paralysis leading to a decrease in peristalsis
-leads to constipation (treat with laxative)
Effects of opiods on GU
-spasm of ureter
-reduce urine production (ADH)
-depressed sexual activity
-passed to neonates
How do you stop the withdrawal effects?
give them more of the drug
cross tolerance of opioids
if you are tolerant to one opioid you are tolerant to all of them
Mechanism for opioid tolerance
-dysfunction in G-protein receptor
-change in the NMDA receptor action (pre- and post-synaptic events)
Effects of opioid on immune system?
-immune supressive
-mu effect
Absorption of opioids
-codeine is absorbed much faster than morphine, therefore more addictive
-heroin crosses the blood brain barrier 2.5 times as easily than morphine
metabolism of opioids
-the first metabolite of morphine is active
-activation is in the liver
Side effects of opiodis
-dizziness, nausea, vomiting
-constipation
-biliary colic
-allergic rxns
-hypotension (give with antihistimine)
-respiratory problems
What other drugs do opioids interact with?
-tricyclic antidepresents
-phenothiazines
-barbiturates that enhance respiratory depression
Tramadol (ULTRAM)
-codeine analog
-mild or moderate pain
-binds to mu-opioid receptors
-inhibits amine reuptake
-less nausea and constipation
-thought to have less abuse potential, but not really true
Methadone (DOLOPHINE)
-orally, longer acting
-this avoids dependence
-heroin detoxification (LAAM)
-long-acting methadone analog
-well absorbed by all routes
Propoxyphene (DARVON)
-half as analgestic as codeine
-well absorbed
-different euphoria
-abuse potential is lower
meperidine
-consists of a few analogs
-shorter duration of action, similar to morphine
-antimuscarinic effects causing tachycardia
-less constipation
Absorption and excretion of meperidine
-rapid by all routes
-metabolism by liver
-is excreted by urine
Toxic effects of meperidine
-seizures caused by normeperidine accumulation
-this is seen more in patients with kidney problems
-otherwise similar side effects to morphine
-interacts with the tricyclic antidepressancts, phenothiazines and barbituates
-CNS excitation with MAO inhibitors
Fentanyl
-type of meperidine
-used short term or chronically ill
-patches, lozenges or lollipops
Opiod Antagonists
-pretreatment prevents the action of the agonist (addicitive opioid)
-will precipitate withdrawal in a chronic user
What are two antagonists used to treat heroin addicts?
naloxone and naltrexone
Alvimopan (ENTEREG)
-opioid antagonist that relieves bowel obstruction following bowel resection
-doesn't cross blood brain barrier
What is methylnaltrexone (RELISTOR) used for?
-It is an antagonist to opioid
-form of the antagonist naltrexone
-doesn't cross blood brain barrier
-reduces constipation
Partial Agonists
-agaonist properties when given alone
-antagonist properties when gievn with an opioid
Nalophine
-k-opioid effects
-blocks mu receptors so it can precipitate withdrawal
-used to diagnose physical dependence
Butorphanol (STADOL)
-similar to pentazocine (inc HR + BP)
-moderate to severe pain
-low abuse/dependence
-better for acute
Pentazocine (TALWIN)
-oral low level analgestic
-used for those that are addicted
-can't substitute to sustain addiction
-may precipitate withdrawal in chronic users
-may increase HR and BP
Nalbuphine (NUBAINE)
-some analgestic but no cardiovascular or hypotension problems
Buprenorphine (BUPRENEX)
-mu-agaonist activity
-antagonist if given with morphine
-good substitute for heroin maintenance
-REDUCES CRAVING
Antitussive agents
codeine
dextromethorphan
benzonatate (related to procaine)
*What would you use to treat biliary/renal colic?*
meperidine
*For moderate pain what drug would you choose?*
-codeine
-sometimes combined with aspirin or acetaminophen
*What types of drugs would you use for diagnostic procedures?*
short acting
*Which drug is widely used as a substitue for heoin detoxification?*
methadone
*How do you reverse respiratory depression in opioid overdose?*
naloxone/nalemefene IV
*what opioid can you use to treat dyspnea from left ventricular failure?*
morphine
What is it about a nerve fiber that makes it more susceptible to an anesthetic?
1) Diameter: smaller diameter is more susceptible, large surface area:volume ratio
2) Frequency of Discharge: on open channel is more susceptible
3) Myelination: less myelination makes it more susceptible
Which surface anesthetics limit antibiotics?
The ester linked anesthetics (PTC) are metabolized to a metabolite that interacts with the antibiotic sulfonamide