Opioids Flashcards
What can opioids be used for?
Opioids are good drugs to help deal with severe pain such as in cancer patients
What are 2 major locations of pain sensation?
2 major locations involved in the sensation of pain:
1. Peripheral nerves – non-steroidal anti-inflammatory drugs
2. Central nervous system (spinal cord)
What plant do opioids come from?
The opium poppy
What are opiates?
- Alkaloids found in the opium poppy (high concentration of morphine, used to treat severe diarrhea and pain)
What is heroin?
Heroin is a derivative of morphine
How is opium harvested?
Harvested – scratch seed pods with a knife, the juice comes out, scrape it off
The same pod can be scratched and scrapped many times
What was morphine named for?
Morpheus – the Greek goddess of dreams, gives morphine its name because you get sleepy when you take morphine
Which administration gives a faster effect?
Smoking gives a faster effect than eating it
Morphine oral administration?
When it taken orally, it is metabolized in the liver, less gets to the blood fast, less likely to be addictive, no high effect
When was opioids mechanism of action discovered?
1975 – discovery of endogenous opioids, mechanism of action, after they were widely used
Types of opiates/opioids?
Morphine (heroine is a derivative)
Codeine (weaker than morphine, better absorbed orally)
- Opiates are drugs derived from opium
- There are many side effects
- Many different derivatives where synthesised to try to find a similar drug with less side effects
- Opioids are drugs with morphine-like action
Fentanyl, methadone
Is heroin more potent than morphine?
Yes, more potent = more addictive
What is Naloxone?
Naloxone – antagonist (used to save lives of people who overdose) acts on the mu receptor
What is Buprenorphine?
It is a weak agonist of the mu receptor, morphine is an agonist
Where are opioid receptors found?
- Presynaptic membranes: decrease transmitter release
- Postsynaptic membranes: hyperpolarize membrane, open K+ channels
What are the 4 types of opioid receptors?
Delta
Kappa
Mu
Nociceptin
How does the mu receptor activation cause pain inhibition?
Main one is the mu receptor (decrease the influx of Ca2+, increase the outflux of K+, hyperpolarize membrane)
Decreases the release of neurotransmitters
Presynaptic decrease in transmitter release
Postsynaptic hyperpolarization
Receptor turnover is important why?
GPCR, endosome or lysosomes
Internalized, recycled or degraded
Mechanism promoting tolerance – recycling can be modified (increased or decreased) can be put back into the membrane
Receptor plasticity and morphine?
Synthesize more receptors
Pain stimulation alters the number of receptors to the membrane
Chronic morphine use alters receptor trafficking
Effects of opioids? (4)
- Analgesia
o Relief in pain in absence of impairment in other sensory modalities
o No change in sight, movement, hearing, touch
o “Soldiers disease” used in war - Gastrointestinal effects, inhibit motility
- Cough suppression
- Euphoria
Which opioid receptor is involved with analgesia, decreased respiration, GI tract constipation?
The mu receptor, less selective responses at higher doses
Morphine Administration?
Absorption: oral, rectal, injection, GI absorption is slow and incomplete
- The usual rout is intramuscular, subcutaneous, or Intravenous
- Inhalation is rapidly absorbed
- Liver inactivation, will get to spinal cord, brain – takes more time, not as addictive, good for pain relief
For chronic pain, pumps can be placed under the skin to release more of the drug
Morphine/Heroin distribution?
Distribution: only 20% crosses the Blood Brain Barrier, heroin is more lipid soluble (can cross BBB more)
Morphine metabolism, half life?
Metabolism: in liver, half life is 2-4hours, the metabolites are different depending on if the drug was administered orally of parenteral (injection)
