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What are the STRONG opioid agonists?
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What are the moderate opioid agonists?
Codeine
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What are the prototype mixed agonist-antagonist opioids?
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What are the opioid antagonists?
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What is phasic pain?
sharp and pricking. a type of acute pain
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what is tonic pain?
dull, throbbing, aching pain. a type of acute pain
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Define Opiate:
drug derived from juice of opium poppy (morphine and codeine)
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Define Opioid:
natural or synthetic compounds with actions that mimic morphine
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Define Opiopeptin:
endogenous opioid peptides. includes endorphins, dynorphins, enkephalins
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define Narcotic:
legal term for these drugs, but not medical term. derived from greek word for stupor
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Mechanism of action (simple):
interact with endogenous opioid receptors. Receptors are found mostly in the brain and spinal cord.
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what are the 3 types of opioid receptors?
μ, δ, κ
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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.
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μ has high affinity for what?
- Morphine, enkephalins, B-endophin.
- endorphins>enk>dyn
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μ mediates:
opioid induced analgesia, + reinforcement, resp depression, miosis, decreased GI motility, neuroendocrine fx
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δ receptors have a high affinity for what?
- enkephalins, and B-endophin.
- enk>endo and dyn
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δ receptors do what?
antinociception, motor integration, cognitive function
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κ receptors have a high affinity for?
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κ receptors do what?
regulate food intake, temp control, GI motility, pain perception, neuroendocrine fx
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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
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Mechanism of opioids
- inhibit release of excitatory response NT's.
- acitivate pain inhibitory pathways form spinal cord
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Opioid fx on CNS:
- analgesia
- eu or dysphoria
- sedation
- resp depression
- cough suppression
- Miosis (pupil constriction)
- Emesis
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Opioid fx on CV system:
hypotension and vasodilation
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Opioid fx on GI system:
constipation
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Opioid fx on GU system:
urinary retention, prolonged labor
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Opioid fx on neuroendocrine system:
stimulates release of ADH and prolactin. inhibits leutenizing hormone
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Opioid fx on dermis:
flushing, itching, urticaria
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Tolerance to most fx except:
constipation, miosis
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Can cross-tolerance occur?
YES
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Withdrawal syndrome:
lacrimation, rhinorhea, yawn, chills, hypervemitlation, muscle spasms, vomiting, anxiety and hostility
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what are strong agonists used to treat? ehat drugs are in this category?
- severe pain.
- morphine,heroin, methadone, meperidine, fentanyl
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strong agonists have a strong affinity for which receptor?
MU!!!
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Facts about morphine:
- active ingredient in OPIUM
- 4-6 hr duration
- has active metabolite: morphine-6-glucuronide
- TX of sever pain
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Methadone facts:
- LONG duration- 15-20 hrs
- orally effective
- used for detox and withdrawal
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what drug is used to treat withdrawal of morphine and heroin?
methadone
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Fentanyl facts:
- 80x potent than morphine
- rapid onset, short duration
- used as an anesthesia adjunct
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Name a moderate antagonist:
Codeine
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Codeine facts:
- 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
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Moderate agonists are used for _______ and and have potential for _______. They are usually _______ with other non-opioid analgesics.
moderate pain tx, abuse, mixed
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Mixed agonist-antagonists:
have agonist fx on one receptor type, antagonist on others
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What are the Mixed agonist-antagonists:
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pentazocine facts:
- k-agonist, weak mu antagonist
- parenteral formula used as preanesthetic
- orally for moderate to severe pain
- precipitates a withdrawal syndrome in morphine abuser
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Buprenorphine facts:
- potent, long lasting partial mu-agonist
- slow dissociation from mu-receptor makes it resistant to naloxone
- effective tx for cocaine and heroin abusers
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What are the opioid antagonists?
naloxone and naltrexone
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naloxone facts:
- 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
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naltrexone:
- long lasting competitive antagonist (24hrs)
- used as maintenance drug for addicts
- tx of alcohol craving
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what drug is used to treat alcohol craving in chronic alcoholics?
naltrexone
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what drug is resistant to naloxone reversal?
buprenorphine
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what drugs will cause withdrawal syndrome in opioid abuser?
pentazocine, naloxone
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what is the active metabolite of morphine?
morphine-6-glucuronide
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