Opiods/Pain Flashcards
What receptor do opioids primarily act on?
Mu opioid receptor
What are the three known opioid receptors?
Mu, kappa, delta
How do opioids work generally?
They bind opioid receptors and inhibit ionic currents of nerve fibers in the CNS responsible for transmitting nociception and also indirectly activate the descending inhibitory system in the periaqueductal grey by inhibiting inhibitors of the periaqueductal grey.
How do opioid antagonists work?
They reversibly bind to opioid receptors without agonist activity, which prevents actions of exogenous and endogenous opioids (no clinical effect without opioid agonists)
How do agonist-antagonist opioids work?
Agonist actions on kappa receptors, antagonist actions on mu receptors
How do partial opioid agonists work?
They act as agonists on mu opioid receptors but cannot fully activate the receptor
What are the dose-dependent effects of opioids?
Analgesia, sedation/euphoria, respiratory depression, nausea, constipation, pruritis, and miosis.
Which opioid has the most histamine release?
Morphine
Which opioid has many notable active metabolites that can become problematic in renal failure?
Morphine
Which opioid is largely banned due to a toxic metabolite that can accumulate in renal failure and cause seizures?
Meperidine
Which opioid is a prodrug that does not convert to an active drug in some patients with genetic variants?
Codeine
Which opioid is commonly used for acute pain but does not often lead to histamine release or have many active metabolites?
Dilaudid
What is the active substance in drugs like oxycodone?
Oxycontin
Which opioid has a long half-life, lack of active metabolites, but can cause long QT syndrome at high doses?
Methadone
Which potentially fatal side effect is associated with methadone?
Methadone
What are commonly used agonist/antagonist drugs?
Butorphanol, nalbuphine
What is buprenorphine?
The only clinically available partial agonist available in the united states
What is naloxone?
A opioid antagonist
What does the term opiate refer to?
Drugs derived directly from opium
What does opioids refer to?
All opiate receptor agonists
What two drugs are considered weak opioids?
Codeine and propoxyphene
What are the two alkaloid types of opium?
Phenanthrene series and benzylisoquinoline series
How do opioid receptors work?
They work via G proteins to inhibit cellular adenylyl cyclase activity, activate potassium currents, and suppress calcium currents mostly in the pain transmitting fibers of the CNS
Why is their interpersonal variation in opioid response?
Splice variants in the three opioid receptors
What causes respiratory depression from opioids?
Activation of mu2 receptors in the brainstem, which leads to decreased ventillatory rate and reduced tidal volume
What is miosis?
Excessive constriction of pupils of eye
What causes miosis in opioid use?
Direct mu and kappa activation of the parasympathetic outflow to the eye. Classic finding of opioid usage.
What causes the GI effects of opioids?
Decreased gastrointestinal transit via action on mu2 receptors within the CNS and peripheral nerve plexus
Can opioids be used in pregnancy?
They cross the placental barrier, but have low risk of teratogenicity so they are safe to use for acute administrations.
What are symptomsof opioid withdrawal?
Sympathetic nervous system hyperactivity (sweating, cramping, diarrhea, elevated HR and BP, hyperventilation, pupil dilation)
What are possible drug interactions with opioids?
Anything that causes sedation on its own can cause severe and dangerous levels of sedation with opioids
What causes overdoses in opioid use?
Excessive ventilatory depression
What morphine metabolite causes excessive sedation in patients with renal failure?
Morphine-6-glucuronide
What is the bioavailability of morphine?
Low because it is poorly absorbed in oral formulations (higher in IM or subcutaneous injections)
How is fentanyl used?
Transdermal patch, IV (forsurgery)
What is tramadol?
A partial opioid agonist, partial SSRI that is used for pain relief, particularly for back pain
A patient in the ICU is recovering from a surgical resection of dead bowel. The patient is septic and requires hemodialysis three times a week. He is being given meperidine every 3 hours for control of his pain and to supplement his sedation. After two days on this regimen, you are called to his bedside because of seizures. The most appropriate therapy would be
a) naloxone to treat the meperidine induced seizure
b) benzodiazepines to treat meperidine metabolite induced seizure
c) naloxone tocontrol effects of delayed meperidine clearance
d) nalbuphine to antagonize the effect of the opioid while providing some analgesia
e) urgent dialysis to remove the accumulated meperidine
b) benzodiazepines to treat the meperidine metabolite induced seizure
normeperidine is a seizure inducing metabolite of meperidine normally cleared by the kidney. It has nothing to do with opioid receptors and seizures from it should be treated like any seizure.
A patient with oropharyngeal cancer is requiring management of pain due to tumor erosion into his mandible. A long duration opioid is desired to avoid his having to take medication frequently. Due to difficulty swalling, however, he can only consume liquids or tablets that are crushed and placed in apple sauce. The best option is
a) sustained release morphine pills
b) sustained release oxycodone pills
c) hydromorphone pills
d) methadone
e) fentanyl lollipop
d) methadone
Sustained release pills lose their long duration when you crush them, and the fentanyl lollipop is for acute pain. Only methadone is inherently long acting by virtue of its long half life.
A patient comes to you suffering from pain following knee surgery 3 days ago. He reports that the opioid pain medication that he received from the orthopedic surgeon causes nausea and dysphoria but does nothing for his pain. He notes that a different opioid medication that he had from a prior surgery works well, and he requests you prescribe this for him instead. What would the scientific justification be for prescribing a different opioid?
Different people have different splice variants in opioid subreceptors that have a variety of affinities for different drugs
Which opioid has the longest half life?
Methadone