9 Opioids, Local Anesthetics

Question 1

potency of 4 local anesthetics

Answer 1

• least potent –> most:

lidocaine > proxymetacaine

Question 2

MOA of local anesthetics

Answer 2

• 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

Question 3

pharmacokinetics of local anesthetics

Answer 3

• 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

Question 4

elimination of local anesthetics

Answer 4

• metabolism by plasma esterases or hepatic P450s (lidocaine) to water-soluble metabolites
• excreted in urine

Question 5

toxicity of local anesthetics

Answer 5

• CNS effects - sleepiness, dizziness, seizures

- CVS effects - decreased contractility, vasodilation, hypotension, CV collapse

Question 6

3 ways local anesthetics are fomulated

Answer 6

• injectable +- epinephrine
• topical
• spray

Question 7

specific uses of local anesthetics

Answer 7

• local
• • injectable - surgical, dental
• • surface - topical gel/spray on skin, wounds, burns, mucous membranes
• • ophthalmic solutions (proxymetacaine)
• • dental - non-injectable (teething pain, cankers)

Question 8

specific uses of regional anesthetics

Answer 8

• spinal - injection into CSF into subarachnoid space
• epidural - long periods
• nerve blocks - around nerve

Question 9

what are analgesics and 3 types of analgesics

Answer 9

• relieve pain without loss of consciousness

- eg. acetaminophen, NSAIDs, opioid drugs

Question 10

what are opioids used for?

Answer 10

• moderate to severe pain
• post-op pain
• terminal condition pain
• degenerative conditions

Question 11

difference between opiates and opioids

Answer 11

• opiates are natural
• • eg. morphine, codeine
• opioids are natural and synthetic
• • eg. fentanyl, naloxone

Question 12

uses of opioids

Answer 12

• analgesia - acute, chronic
• anesthesia
• cough suppression
• diarrhea
• opioid addiction

Question 13

opioid MOA

Answer 13

opioid agonists bind to u, K, d GPCRs –> analgesia

Question 14

where are mu and kappa opioid receptors located?

Answer 14

• mu - brain
• kappa - spinal cord
• delta - both

Question 15

morphine pharmacokinetics ADME

Answer 15

• 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

Question 16

morphine pharmacologic effects

Answer 16

• 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

Question 17

clinical uses of morphine

Answer 17

• analgesia for post-op pain
• use as premedication
• pain relief

Question 18

clinical uses of codeine

Answer 18

• mild-moderate pain
• formulated with acetaminophen
• less sedation/resp depression
• addiction less severe

Question 19

clinical uses of dextromethorphan

Answer 19

• cough suppression

- not addictive

Question 20

clinical uses of oxycodone

Answer 20

• derivative of morphine
• oral
• formulated with aspirin or acetominophen
• moderate to severe pain
• time-release oral form

Question 21

synthetic opioid agonist - fentanyl

Answer 21

• rapid onset, short duration
• analgesia, 100x more than morphine
• IM, patch, epidural (labor)

Question 22

opioid antagonist - naloxone

Answer 22

• 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

Question 23

2 opioids to control diarrhea

Answer 23

• loperamide - limited access to brain
• diphenoxylate - atropine added to decrease abuse
• stool in large colon longer
• more water reabsorbed from stool