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Types of opioids
- Naturally occuring
- Semi-synthetics
- Synthetics
- Opioid antagonists
- Endogenous opioids
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Naturally occuring
- Opium
- 2 major alkaloids:
- Morphine
- Codeine
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Semi-synthetics
- Heroin
- Analgesics:
- Hydromorphone - potent
- Hydrocordone - less potent
- Oxycodone - strongest
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Synthetics
- Mimic actions of opiates
- Phenylpiperidines
- Methadone and congeners
- Benzomorphans
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Opioid antagonists
- Naloxone - treat heroin overdose
- Naltrexone
- Suboxone
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Endogenous opioids
- Enkephalins
- Endorphins
- Dynorphins
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Analgesic Potency
- Mild to moderate pain -> codeine, propoxyphene
- Moderately severe -> meperdine
- Severe pain -> heroin, hydromorphone
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Major effects
- Analgesia
- Euphoria
- Nausea and vomiting
- Respiratory depression
- Miosis
- Gastrointestinal effects
- Cough suppression
- Motor effects
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Sensitization
- Psychomotor stimulant effects
- Rewarding effects
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Opioid peptide gene families
- Proopiomelanocortin (POMC) -> beta-endorphin
- Proenkephalin
- Prodynorphin -> dynorphins A and B
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Mu receptor
- Morphine
- Endorphins
- Thalamus and caudate
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Mu compound mechanism
- Increase DA cell firing
- Increase DA release in nucleus accumbens
- Locomoter activation
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Kappa compound mechanism
- Decrease DA cell firing
- Decrease DA release
- Decrease locomotion
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Gastrointestinal effects
- Mediated by mu and kappa sites
- In stomach, small and large intestines
- Decreased motility -> constipation
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