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What are the STRONG opioid agonists?
What are the moderate opioid agonists?
What are the prototype mixed agonist-antagonist opioids?
What are the opioid antagonists?
What is phasic pain?
sharp and pricking. a type of acute pain
what is tonic pain?
dull, throbbing, aching pain. a type of acute pain
drug derived from juice of opium poppy (morphine and codeine)
natural or synthetic compounds with actions that mimic morphine
endogenous opioid peptides. includes endorphins, dynorphins, enkephalins
legal term for these drugs, but not medical term. derived from greek word for stupor
Mechanism of action (simple):
interact with endogenous opioid receptors. Receptors are found mostly in the brain and spinal cord.
what are the 3 types of opioid receptors?
μ, δ, κ
Mechanism of action of opioid receptors:
- inhibit voltage-gated Ca channels and decrease the release of NT from presynaptic terminals of nociception afferents.
- *mu also has post-synaptic action, activing inward K.
μ has high affinity for what?
- Morphine, enkephalins, B-endophin.
opioid induced analgesia, + reinforcement, resp depression, miosis, decreased GI motility, neuroendocrine fx
δ receptors have a high affinity for what?
- enkephalins, and B-endophin.
- enk>endo and dyn
δ receptors do what?
antinociception, motor integration, cognitive function
κ receptors have a high affinity for?
κ receptors do what?
regulate food intake, temp control, GI motility, pain perception, neuroendocrine fx
where are opioid receptors found?
- primary afferents and spinal cord pain transmission neurons.
- also descending pain pathways- PAG and RVM
- brain stem, hypothalmus, GI tract
Mechanism of opioids
- inhibit release of excitatory response NT's.
- acitivate pain inhibitory pathways form spinal cord
Opioid fx on CNS:
- eu or dysphoria
- resp depression
- cough suppression
- Miosis (pupil constriction)
Opioid fx on CV system:
hypotension and vasodilation
Opioid fx on GI system:
Opioid fx on GU system:
urinary retention, prolonged labor
Opioid fx on neuroendocrine system:
stimulates release of ADH and prolactin. inhibits leutenizing hormone
Opioid fx on dermis:
flushing, itching, urticaria
Tolerance to most fx except:
Can cross-tolerance occur?
lacrimation, rhinorhea, yawn, chills, hypervemitlation, muscle spasms, vomiting, anxiety and hostility
what are strong agonists used to treat? ehat drugs are in this category?
- severe pain.
- morphine,heroin, methadone, meperidine, fentanyl
strong agonists have a strong affinity for which receptor?
Facts about morphine:
- active ingredient in OPIUM
- 4-6 hr duration
- has active metabolite: morphine-6-glucuronide
- TX of sever pain
- LONG duration- 15-20 hrs
- orally effective
- used for detox and withdrawal
what drug is used to treat withdrawal of morphine and heroin?
- 80x potent than morphine
- rapid onset, short duration
- used as an anesthesia adjunct
Name a moderate antagonist:
- 0.5% of opium
- not active until metabolized to morphine
- given for mild to moderate pain in combo with aspirin and tylenol
- included in many cough syrups
Moderate agonists are used for _______ and and have potential for _______. They are usually _______ with other non-opioid analgesics.
moderate pain tx, abuse, mixed
have agonist fx on one receptor type, antagonist on others
What are the Mixed agonist-antagonists:
- k-agonist, weak mu antagonist
- parenteral formula used as preanesthetic
- orally for moderate to severe pain
- precipitates a withdrawal syndrome in morphine abuser
- potent, long lasting partial mu-agonist
- slow dissociation from mu-receptor makes it resistant to naloxone
- effective tx for cocaine and heroin abusers
What are the opioid antagonists?
naloxone and naltrexone
- competitive antagonist at mu>delta=k
- 1-2 hr duration
- no fx on normal individuals
- will cause withdrawal in opiate abusers
- IV use to reverse opioid overdose
- long lasting competitive antagonist (24hrs)
- used as maintenance drug for addicts
- tx of alcohol craving
what drug is used to treat alcohol craving in chronic alcoholics?
what drug is resistant to naloxone reversal?
what drugs will cause withdrawal syndrome in opioid abuser?
what is the active metabolite of morphine?