Chpt. 11 Flashcards
What is an opioid agonist?
An opioid agonist binds to opioid receptors and produces full biological effects.
E.g., morphine, heroin, and fentanyl.
What is a partial opioid agonist?
A partial opioid agonist binds to receptors but has less biological effects.
E.g., buprenorphine.
What is an opioid antagonist?
An opioid antagonist is structurally similar to opioids but has no efficacy and can prevent or reverse the effect of opioids.
What is a mixed agonist-antagonist?
A mixed agonist-antagonist acts as an agonist at one receptor subtype and an antagonist at another.
Why is heroin a more common drug of abuse than morphine?
Heroin is more dissolvable than morphine and causes a more intense ‘rush’ of euphoria.
Heroin is also metabolized to morphine within the brain.
Why is fentanyl so dangerous?
Fentanyl is a synthetic opioid that is 50x more potent than heroin and 100x more potent than morphine.
Carfentanyl is 100x more potent than fentanyl and works rapidly.
Carfentanyl
A synthetic drug used as a large animal tranquilizer; is 100x more potent than fentanyl and works rapidly; it’s mixed with heroin or prescription painkillers, which has contributed to the surge in OD deaths.
What are the principal acute effects of opioids on the brain and body?
CNS effects include pain relief, constricted pupils, drowsiness, inability to concentrate, and dreamy sleep. Other acute effects include cough suppression, decreased GI motility, nausea, and vomiting.
What are the three major opioid receptor subtypes?
Mu (µ), Kappa (κ), & Delta (δ)
Mu (µ)
Activated by morphine. Mediates the euphoric properties of the opioids, as well as sedation, GI effects, respiratory depression, and nausea. Located in brain, spinal cord, and periphery
Kappa (κ)
Activated by ketocyclazocine. Mediates the aversive properties of the opioids, as well as spinal analgesia and sedation; little or no respiratory depression
Delta (δ)
Activated by enkephalins. Mediates spinal and supraspinal analgesia, but agonists are poor analgesics.
What are the locations and functions of the three endogenous opioid systems?
Endorphins bind to mu receptors for pain relief and euphoria; Enkephalins bind to delta receptors for pain modulation; Dynorphins bind to kappa receptors and can produce dysphoria.
Does tolerance occur with chronic opioid use?
Yes, opioid tolerance occurs when repeated use leads to diminished effects, requiring higher doses.
This includes metabolic, pharmacodynamic, and behavioral tolerance.
What neural adaptations are thought to be involved in opioid tolerance?
Tolerance: the diminishing effects of a drug with repeated use.
Cross-tolerance: individuals tolerant to one opioid may show reduced sensitivity to others.
Sensitization: increase in drug effects that occurs with repeated administration.
What are the major signs and symptoms of opioid withdrawal?
Withdrawal signs include sweating, yawning, runny nose, teary eyes, goosebumps, vomiting, diarrhea, tremors, chills, muscle aches, anxiety, agitation, restlessness, and intense cravings.
What are the pros of using medication-assisted treatment (MAT) for opioid dependence?
Pros include reduced opioid cravings, decreased illicit drug use, decreased disease risk, and long-acting effects.
What are the cons of using medication-assisted treatment (MAT)?
Cons include potential for addiction, overdose risk, and not fully eliminating cravings.
What other forms of treatment are available for opioid use disorder?
Other treatments include detoxification (assisted or unassisted), methadone for withdrawal symptoms, clonidine to reduce NE activity, and electroacupuncture.
Why are opioids such dangerous drugs of abuse?
Opioids have significant reinforcing properties, may lead to tolerance and physical dependence, and carry a risk of overdose.
