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Opioid Analgesics

Terms in this set (26)

what is the crude source of opium?
seed pod (opium poppy)
- contains morphine and codeine
- first isolated in the early 1800s
what are the 3 receptor families in opioid receptors?
mu, kappa, and delta
*mu= primary analgesia receptor!

they are all G-protein coupled receptors associated with ion channels (K+, Ca++), goal of opioids= hyperpolarization
main action of Mu receptor:
analgesia (but also resp. depression, sedation, dec. GI motility, and physical dependence)
main action of Kappa receptor:
sedation (but also analgesia and dec. GI motility)
main action of Delta receptor:
modulates mu receptor activity
what are the 3 ways by which opioids are classified?
by drug source, chemical class, and pharmacologic activity
with are the 2 naturally-occurring opioids?
morphine and codeine
which opioid class are the majority of our dental Rx's from?
semisynthetic opioids
MOA of opioids:
stereospecific bringing to G protein-coupled opioid receptors on neural cell membranes
- Mu receptors (analgesia)

impede pre- and post-synaptic neuron firing by decreasing excitatory transmitter release and closing calcium channels/opening K+ channels (hyperpolarize the membranes so AP can't go up the SC to the brain stem)

targeting the neural cells in CNS and brain, peripheral sensory nerves, and smooth muscle (ex. GI and urinary tract)
routes of opioid administration:
oral, transdermal, SQ, and IM routes
--> first-pass effect influences the clinical effect of oral admin. (ex. morphine)
distribution/accumulation of opioids:
- rapid distribution
- accumulate in fatty tissues
- can cross the placenta
- variable crossing of the BBB (fentanyl > morphine based on lipid-solubility)
opioid metabolism/elimation:
3 methods of metabolism:
- liver conjugation and glucuronidation into active metabolites (ex. morphine --> morphine-6-glucuronide, analgesia)
- CYP450 oxidation (fentanyl, meperidine, oxycodone, hydrocodone, codeine)
- tissue and plasma esterases (ex. heroin)

renal elimination
what does codeine get metabolized to?
morphine (2D6)
pharmacologic effects of opioids:
analgesia for moderate to severe pain
- increases pain threshold
- depress reaction to pain (really more takes away the reaction to pain than actually takes away the pain)

euphoria

sedation (drowsiness and cognitive impairment)

cough suppression (antitussive use, lower doses than for analgesia)

decrease GI motility and works as anti-diarrheal
adverse RXNs:
- respiratory depression --> medullary respiratory center CO2 response diminished, most common COD
- nausea and emesis (CRTZ in medulla)
- xerostomia
- constipation and urinary retention
- miosis (sign of OD)
- itching, flushing, urticarial (from histamine release, but true allergy uncommon)
CV effects of opioids:
- depress vasomotor center and stimulate vagus nerve
- bradycardia and hypotension
- potential hypotension and syncope
how can you limit adverse experiences for specific people?
dosing titration (some people have more tolerance than others)
what is a weaker/less potent opioid?
codeine (very weak)
- only given in combination with acetaminophen
- CYPSD6 demethylation to morphine
what are some more potent opioid options?
oxycodone (immediate and extended release, often given in combination with ibuprofen and acetaminophen), fentanyl, hydromorphone
more info about Hydrocodone
- analgesia comparable to morphine
- metabolites include hydromorphone
- given in combination with acetaminophen
more info about Fentanyl:
- synthetic related to merperidine
- 100x potency of morphine
- rapid onset and short duration of action IV
- available IV, nasal, lollipop, transdermal patch (not oral)
interesting things about Tramadol:
has unique complimentary MOAs
- Mu agonist (weak)
- Also a weak inhibitor of norepinephrine and serotonin repute in pain pathways

less resp. depression CV effects than morphine

contraindicated in pts. with a history of seizures

schedule IV drug (less addictive)
signs of physical dependence on opioids:
irritability, tachycardia, nausea, tremors
what drug is given for opioid addiction?
Methadone (Dolophine)
- for opioid withdrawal and maintenance programs
- Norepinephrine and serotonin reuptake inhibitor
- Mu agonist only
- for chronic and neuropathic path

Methadone for addiction
what drug is given in cases of opioid overdose?
Naloxone (Narcan)
- competitive antagonist of ALL mu, kappa, and delta receptors
- reverses respiratory depression (IV w/in 1-2 minutes, IM or SQ within 2-5 minutes)

Naloxone for overdose
another option for opioid overdose treatment that is good for both opioid and alcohol dependence
Naltrexone
- longer DOA
- oral dosage form
- for maintenance therapy and to prevent relapse
- may cause withdrawal
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