9 Opioids, Local Anesthetics Flashcards
(23 cards)
potency of 4 local anesthetics
- least potent –> most:
lidocaine > proxymetacaine
MOA of local anesthetics
- decrease nerve impulses
- block voltage-sensitive Na+ channels –> decrease Na+ influx
- prevent depolarization
- in afferent pain pathways –> block pain
- in efferent vasomotor fibers –> causes vasodilation
pharmacokinetics of local anesthetics
- block channels
- with vasoconstrictor (eg. epinephrine), slow blood flow
- slows drug absorption
- decrease toxicity and increase duration
- delay healing (decreased blood flow)
- don’t use where end-artery supplies –> necrosis
elimination of local anesthetics
- metabolism by plasma esterases or hepatic P450s (lidocaine) to water-soluble metabolites
- excreted in urine
toxicity of local anesthetics
- CNS effects - sleepiness, dizziness, seizures
- CVS effects - decreased contractility, vasodilation, hypotension, CV collapse
3 ways local anesthetics are fomulated
- injectable +- epinephrine
- topical
- spray
specific uses of local anesthetics
- local
- injectable - surgical, dental
- surface - topical gel/spray on skin, wounds, burns, mucous membranes
- ophthalmic solutions (proxymetacaine)
- dental - non-injectable (teething pain, cankers)
specific uses of regional anesthetics
- spinal - injection into CSF into subarachnoid space
- epidural - long periods
- nerve blocks - around nerve
what are analgesics and 3 types of analgesics
- relieve pain without loss of consciousness
- eg. acetaminophen, NSAIDs, opioid drugs
what are opioids used for?
- moderate to severe pain
- post-op pain
- terminal condition pain
- degenerative conditions
difference between opiates and opioids
- opiates are natural
- eg. morphine, codeine
- opioids are natural and synthetic
- eg. fentanyl, naloxone
uses of opioids
- analgesia - acute, chronic
- anesthesia
- cough suppression
- diarrhea
- opioid addiction
opioid MOA
opioid agonists bind to u, K, d GPCRs –> analgesia
where are mu and kappa opioid receptors located?
- mu - brain
- kappa - spinal cord
- delta - both
morphine pharmacokinetics ADME
- A - oral, IM, IV, SC
- morphine IM
- codeine orally
- D
- morphine poorly distributed to brain
- codeine crosses BBB
- cross into placenta if lipophilic
- M
- hepatic –> inactive glucuronide conjugates
- some codeine –> morphine
- young and old sensitive, can’t metabolize
- E
- urine mostly, some bile –> feces
- side effects if renal/hepatic failure
morphine pharmacologic effects
- CNS
- analgesia, slight sedation
- euphoria
- miosis
- stupor at high doses
- respiratory
- does-dependent depression –> apnea
- resp arrest –> death
- reversal by naloxone
- cardiovascular
- little, but bradycardia at high doses
- may cause histamine release –> vasodilation –> orthostatic hypotension
- GI
- decreases intestinal peristalsis
- constipation
- nausea/vomiting (mu receptor mediated stimulation of chemoreceptor trigger zone
- tolerance/dependence
clinical uses of morphine
- analgesia for post-op pain
- use as premedication
- pain relief
clinical uses of codeine
- mild-moderate pain
- formulated with acetaminophen
- less sedation/resp depression
- addiction less severe
clinical uses of dextromethorphan
- cough suppression
- not addictive
clinical uses of oxycodone
- derivative of morphine
- oral
- formulated with aspirin or acetominophen
- moderate to severe pain
- time-release oral form
synthetic opioid agonist - fentanyl
- rapid onset, short duration
- analgesia, 100x more than morphine
- IM, patch, epidural (labor)
opioid antagonist - naloxone
- blocks opiate receptors, prevents narcotics from binding
- high affinity for mu receptors
- treats opioid-induced respiratory depression
- treats circulatory shock
- reverses narcotic depression post-op
2 opioids to control diarrhea
- loperamide - limited access to brain
- diphenoxylate - atropine added to decrease abuse
- stool in large colon longer
- more water reabsorbed from stool
