Pharm: Opioids and Analgesics Flashcards
How do the mu, delta, and kappa receptors inhibit pain?
When an agonist, like opioids, bind to these receptors, they signal a G-protein cascade that increases potassium conductance on an excitatory cell like a neuron.
This neuron is now hyperpolarized and will not fire without a large stimulus or it may not fire at all. So pain signals are not transmitted.
List the functions of the mu, delta, and kappa receptors
Mu
- Supraspinal and spinal analgesia
- Sedation and inhibition of respiration
- Slow GI transit
- Modulate hormones and NT release
Delta
- Supraspinal and spinal analgesia
- Modulation of hormones and NT release
Kappa
- Supraspinal and spinal analgesia
- Slow GI transit
- Psychomimetic effects
Codeine
Used for moderate pain, converted to morphine by the liver.
MOA: agonist at mu, delta, and kappa receptors
SE: addiction, sedation, depression
Oxycodone, Hydrocodone
Used for mild pain, more mild analogues of codeine
MOA: agonist at mu, delta, and kappa receptors
SE: addiction, sedation, depression
Morphine
Used for intense pain
MOA: agonist at mu, delta, and kappa receptors
SE: addiction, sedation, depression
Hydromorphone
Used for intense pain, more potent than morphine
MOA: agonist at mu, delta, and kappa receptors
SE: addiction, sedation, depression
Methadone
Used for chronic pain in cancer patients due to long half-life.
MOA: agonist at mu, delta, and kappa receptors
SE: respiratory depression (inhibits respiratory center in medulla), torsades de pointes
Meperidine
Used for pain management
MOA: agonist at mu, delta, and kappa receptors
SE: may cause seizures, mydriasis, poor oral bioavailability
Fentanyl
Used in epidurals, short acting to not harm the fetus. 100x more potent than morphine.
MOA: agonist at mu, delta, and kappa receptors
SE: sedation, addiction
Butorphanol
Treatment for opioid addiction, labor pain
MOA: agonist at kappa, partial agonist at mu
SE: sedation, depression
Buprenorphine
Used for chronic pain
MOA: agonist at mu, antagonist at kappa
SE: sedation, depression
Nalbuphine
Used for pre-op and post-op pain, obstetric analgesia
MOA: agonist at kappa, antagonist at mu
SE: sedation, depression
Naloxone
Used as an antidote for opioid intoxication
MOA: competitive antagonist at mu and kappa receptors
shorter half-life than morphine.
SE: can lead to respiratory distress due to opioid reversal
Naltrexone
Treatment of opioid dependence, relapse, alcohol withdrawal
MOA: competitive opioid antagonist
Respiratory depression is a major cause of death from opioid abuse. How do opioids cause this?
Opioid abuse leads to decreased sensitivity of chemo-sensitive neurons that sense pCO2. As CO2 levels rise in the body, the body normally compensates by increasing respiratory rate to prevent acidosis.
