Drugs for Pain Flashcards by Kelli True

Mechanism of action of local anesthetics

Block Na+ channels on the AXON = inability to conduct an action potential

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What are the two classes of local anesthetics?

esters & amides

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Which class of local anesthetics have a higher allergic reaction rate?

esters

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How are the two classes of local anesthetics metabolized?

esters = plasma esterases
amides = hepatic enzymes

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s/s of local anesthetic toxicity

CNS = seizures progressing to coma and death
CV = bradycardia, heart block, decreased contractility, cardiac arrest, vasodilation

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adverse effects of local anesthetics

local anesthetic systemic toxicity (LAST)
allergic reactions
methemoglobinemia (only benzocaine)

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List some ester local anesthetics

procaine
chloroprocaine
cocaine
tetracaine

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List some amide local anesthetics

lidocaine
bupivicaine
ropivicaine
mepivicaine

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What is the general mechanism of action of many of the general anesthetics

chloride influx (via GABA inhibition) & hyperpolarization of neuronal membranes
= depression of CNS activity

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Life threatening adverse effect of inhalation anesthetics?

malignant hyperthermia

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Common side effects of most of the inhaled anesthetics

hypotension
respiratory depression
post-operative nausea & vomiting

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mechanism of action of propofol

promote GABA release
(hyperpolarization of membranes of the CNS, decrease neuronal transmission)

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adverse effects of propofol

respiratory dpression
hypotension
can have bradycardia or reflex tachycardia
injection site pain

propofol infusion syndrome w/ long term infusion

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Positive outcomes of COX inhibition

decreased inflammation
decreased pain
decreased fever

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The production of which substances is inhibited with COX inhibition?

prostaglandins
prostacyclin
thromboxane A2

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Major adverse effects of COX inhibition

increased gastric acid secretion = ulcer development

decreased vasodilation of renal artery = decreased renal blood flow

decreased platelet aggregation = bleeding risk **can be positive effect or adverse effect

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Effects of COX1 inhibition

gastric erosion & ulceration
bleeding
renal impairment

BUT also decreased platelet aggregation (which can prevent MI/CVA, which is good)

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Effects of COX2 inhibition

decreased inflammation
decreased pain
decreased fever

BUT also decreased vasodilation, which can promote MI/CV (which is bad)

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What is another term for the first generation COX inhibitors

nonselective COX inhibitors

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List some first generation COX inhibitors

aspirin
ibuprofen
naproxen
ketorolac
indomethacin

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Who are first generation COX inhibitors contraindicated in?

peds (aspirin)
pregnancy
renal disease
PUD or GI bleeding
bleeding disorders

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How is aspirin different than the other first generation COX inhibitors?

binding is irreversible (higher platelet inhibition)

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How are the second generation COX inhibitors different from the first generation?

only inhibit COX2

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What is the major risk that is present ONLY for second generation COX inhibitors?

CV events
- no suppression of platelet aggregation
- inhibition of vasodilation

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Name a second generation COX inhibitor

celecoxib

mechanism of action of acetaminophen

COX inhibition only in the CNS (not peripherally)

How are the effects of COX inhibitors and acetaminophen different?

acetaminophen = no anti-inflammatory, no decreased platelet aggregation, no GI issues, no decrease in renal blood flow

site of metabolism of acetaminophen

liver

how does toxicity occur in high dose acetaminophen?

too much of the toxic metabolite builds up without enough glutathione to convert it. This toxic metabolite can lead to liver damage

Treatment of acetaminophen toxicity

acetylcysteine (antidote to acetaminophen that can convert the toxic metabolite to inactive form)

what is the max dose of acetaminophen

4g in 24hrs *this max dose may be lower in those w/ preexisting liver disease or EtOH use

What are the 3 opioid receptors?

mu kappa delta

What are the effects of mu agonism

analgesia respiratory depression sedation euphoria physical dependence decreased GI motility

what are the effects of kappa agonism

analgesia sedation decreased GI motility

What do pure opioid agonists do?

agonize mu and kappa

What do opioid agonist-antagonists do?

either agonize or antagonize mu and do the opposite at kappa

How do the effects of opioid agonists/antagonists compared with the pure agonists?

ceiling effect to analgesia less respiratory depression less euphoria lower abuse potential *can precipitate withdrawal in those w/ physical dependence

What do the opioid antagonists do?

antagonize mu & kappa

What are the effects of the opioid antagonists

(NO analgesia) reverse most effects of opioids (can precipitate withdrawal symptoms in those w/ physical dependence)

Which two effects of opioids do patients NOT develop a tolerance to?

miosis decreased GI motility

respiratory effects of opioids

depression (decreased RR) cough suppression

hemodynamic effects of opioids

can slow HR d/t decreased SNS orthostatic hypotension

GI/GU effects of opioids

constipation urinary retention

CNS effect of opioids

euphoria or dysphoria sedation tolerance/physical dependence

pupillary effects of opioids

miosis (constriction)

what is tolerance

larger doses are required to produce same response

what is physical dependence

state in which abstinence syndrome will develop if the drug is abruptly stopped

how to avoid withdrawal symptoms of opioids

taper down doses over time

s/s of opioid withdrawal

mild = yawning/rhinorrhea/sweating severe = sneezing/weakness/N/V/diarrhea/abdominal cramps/muscle pain/spasms

List a few pure opioid agonists

fentanyl morphine meperidine methadone hydromorphone sufentanil remifentanil

How is meperidine different than the other pure opioid agonists

toxic metabolite build up occurs with prolonged use interacts with MAO inhibitors = excitation/seizures

How is methadone different from the other pure opioid agonists

very long 1/2 life - can treat addiction - can also lead to drug accumulation also prolongs the QTc

What is the active metabolite of codeine

morphine

Why do some people not have analgesic effects from codeine

genetic variation in the CYP450 enzyme that metabolizes it

list some opioid agonist-antagonists

nalbuphine butorphanol buprenorphine

List some opioid antagonists

naloxone methylnatrexone naltrexone

What is naloxone used for

opioid OD reversal

Duration of action of naloxone

1hr

what is methylnatrexone used for

opioid-induced constipation that hasn't responded to other interventions

what is naltrexone used for

to block the euphoric effects of opioids (so for opioid/alcohol abuse)

How does tramadol work

weak mu agonism antagonism of NE & serotonin reuptake

adverse effects of tramadol

sedation dizziness/HA constipation seizures suicidal ideation

When increasing opioid dosing when treating cancer pain, what is a major concern?

constipation