Narcotic Analgesics 2
Terms
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- Opiods
- morphine; any type of pain, esp dull and continuous; stimulate opiod receptors; no antiinflammatory or antipyretic effects; central site of action; develop tolerance and dependence
- NSAID
- aspirin; musculoskeletal pain; inhibition of PG synthesis; both antiinflammatory and antipyretic; central or peripheral action; no tolerance or dependence.
- Morphine
- well absorbed by many routes; large first pass effect; large BBB effect; met in liver--glucuronidated and some sulfation; active metabolites excreted in urine; 3 and 6 C's; also demethylation.
- opiod receptors
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1. mu- activated by morphine; fentanyl and naloxone are more selective
2. delta- no drugs selective
3. kappa- activated by ketocyclazocine; preferred by pantazocine, butorphanol, and buprenorphine
*receptors in brain, spinal cord, and GI tract; other receptors assoc with opiod action= sigma--phencyline receptor and epsilon--activated by endogenist agonist beta endorphin - central actions of opiods
- analgesia; sedative effects and narcosis; euphoria; respiratory depression; miosis (species specific); muscular rigidity (fentanyl); sickness; anti-tussive; alter thermoregulatory action; multiple neuroendocrine effects
- peripheral actions of opiods
- GI effects- enteric NS in gut- decreased secretion, increased muscle tone--constipation; morphine constricts sphincter of Oddi in gallbladder; urinary retention; prolongs labor; little effect on CV system (alkaloid character causes some hypotension b/c mast cells release histamine); immunosuppression
- mechanism of action
- bind to and activate opiod receptors; alter the perception of pain; inhibit synaptic transmission (presynaptically); affect intracellular transduction (inhibit cAMP production and block Ca++ channels).
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therapeutic use of morphine
-acute - very severe pain; post op; MI pain; sickle cell vaso-occlusive crisis
- -chronic pain
- usually oral- first pass effect; rectally, spinally, or IV once can't swallow anymore; slow release forms like ms-contin; diarrhea; acute pulmonary edema
- side effects of morphine treatment
- respiratory depression; nausea and vomiting; constipation; dizziness and mental clouding; dysphoria; hypotention; urinary retention; tolerance and physical dependence; interaction with other drugs; additive with other CNS depressants; enhanced action via antidepressants, amphetamines, antihistamines, etc;
- morphine toxicity
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coma; pinpoint pupils (may dilate some b/c of CO2); depressed respiration
GIVE NALOXENE to diagnose if heroin overdose or barbiturates - treatment of narcotic addiction
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1. substitute another narcotic (methadone)
2. detox
3. narcotic antagonists (naloxene and naltexone)
4. clonidine (not an opiod, but cuts down on withdrawal symptoms) - be careful when...
- depressed respiratory reserve; head injury; reduced blood volumes; asthma; biliary colic; renal insufficiency; taking other CNS depressants
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morphine derivatives...
1. hydromorphone - 2-4x more effective; orally effective; aka dilautid
- 2. diacetylmorphine (heroin)
- acetyl groups on hydroxy groups on carbons 3 and 6; easy to make, much more lipophilic; euphoric effects; abuse
- 3. codeine (methylmorphine)
- methyl on 3 position; less potent and effective orally
- 4. hydrocodone or oxycodone
- components of percodan and percoset; abused; good to treat pain; long term release form is oxycotin
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Phenylpiperidine derivatives
1. meperidine - aka Demerol; less potent; normeperidine is toxic metabolite that lowers CNS seizure threshold; interactions with MAOI's and TCA's, etc; short duration of withdrawal
- 2. fentanyl, sufentanyl, and alfentanyl
- much more potent and very lipophilic; fast onset and short duration; effective; maintenance of anesthesia and post op analgesia; fentanyl can cause muscle rigidity in high doses (chest); patch form is slow release and good for chronic pain or radiation patients.
- 3. diphenoxylate and loperamide
- GI drugs to treat diarrhea
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Diphenylheptane derivatives
1. methadone - effective orally; long half life active metabolite; more bioavailable; cheap; avoid stigma!
- 2. propoxyphene
- les efficacious than morphine; rough analgesic effect
- LAAM
- analgesic and used instead of methadone in treating heroin addicts
- Morphinans
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similar structure to morphine
- levorphanol- L isomer- 4-5x more potent than morphine and effective orally
-dextomorphan- D isomer- not analgesic but good anti-tussive effects - opiods with mixed agonist and antagonist activities
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pentazocine--causes increase in bp and heart rate**; component of "Ts and blues"
nalbuphine--less respiratory depression
buprenorphine--now treats heroin addiction b/c longer retraction of withdrawal symptoms, safe, and more potent
nalorphine--not used much
butorhanol--nasal spray for migraine - opiod antagonists
- no analgesic activity; do nothing to normal individuals; precipitate withdrawal symptoms in addicts; naloxone; used in overdose treatment; naltrexone is oral form used in motivated pts
- endogenous opiods
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1. enkephalins- target delta and mu
2. beta endorphin- target delta and epsilon
3. dynorphins- target kappa
4. endomorphin- activated by endomorphins
*no current therapeutic use for opiod peptides