Opioids Flashcards
What are the medical uses of opioids?
Pain = anti-nociceptive
Safe and effective when used appropriately
How do opioids block pain?
They block afferent transmission in the spinal cord/brainstem
Periaqueductal gray
What is a lethal mix of drugs?
Opioids and sedatives
What are the 3 major sources of opioids?
Natural
Semi-synthetic
Synthetic
What are natural sources of opioids?
Opium - alkaloid-laden latex
Morphine, codeine
What are semi-synthetic sources of opioids?
Heroin, hydrocodone, hydromorphone, oxycodone, krokodil
Buprenorphine, etorphine
What are synthetic sources of opioids?
Methadone, meperidine
Tramdol
Fentanyl
What are major narcotics?
Morphine (10%)
Codeine (0.5%)
What is more potent: morphine or opium?
Morphine is 10x more potent than opium
What does CYP2D6 convert codeine to in the brain and liver?
Morphine
What is the result of deficient 2D6?
Codeine has no effect
What is the result of overactive 2D6?
Morphine intoxication
How are semi-synthetic opioids produced?
Produced by modifying a naturally-derived chemical
What makes heroin 10x more lipophilic than morphine?
Two acetyl groups
What is naloxone?
Opioid receptor antagonist
What is methadone?
mew agnoist
When was naloxone synthesized?
1960s
What does naloxone do?
Reverses morphine effects
What did Pert and Snyder discover in the brain?
Opioid receptors
What are the 4 classes of pre and post-synaptic opioid receptors?
mew, delta, kappa, and ORL-1
What do pre-synaptic opioid receptors do?
Modulate NT release
What do post-synaptic opioid receptors do?
Alter membrane potential
How were opioid receptors discovered?
Radioligand binding in brain tissue slices
Where were opioid receptors found in the brain?
Striatal area
Lateral aspect of medial nucleus
Amygdala
Dorsal pons
Periaqueductal gray
Spinal cord
How many endogenous opioids are known?
18 peptide ligands and endorphins
What are endogenous opioids involved in?
Pain, emotional responses, euphoria, eating, stress, seizures, and alcohol dependence
Where are MOR (mew opioid receptors) expressed?
VTA, NAc
PAG
Hypothalamus
LC
Brainstem
Pupils
GI tract
What binds MOR?
Most opioids
What are MOR involved in?
Reward, addiction
Analgesia
Euphoria
Anxiolytic
Respiration, BP
Nausea
Itch
Constriction
Constipation
Where are DOR (delta opioid receptors) expressed?
Neocortex
Striatum
NAc
Substantia nigra
Olfactory bulb
What are DORs bound by?
Enkephalins
Where are KORs (kappa opioid receptors) expressed?
Pituitary
Hypothalamus
PAG
Spinal cord
Others
What are KORs bound by?
Endorphins, dynorphins, PCP, ketamine
Where are orphan opioid receptors expressed?
Limbic system
Spinal cord
What are orphan opioid receptors bound by?
Buprenorphrine
How potent is fentanyl?
100x more potent than morphine
40-50x more potent than heroin
Highly lipophilic
Why are fentanyl derivatives even more potent?
Increased affinity for mu receptors + enhanced entry into the brain = higher potency
How are opioids distributed?
Lipid solubility
Liver
Lungs
Spleen
GI tract
Brain
How are opioids absorbed?
Inhalation
Injection
Ingestion
Insufflation
Sublingual
Rectal
What is the chasing the dragon method?
Heat up on tin foil and inhale the fumes
More commonly smoked in a pipe
What is chasing the dragon linked to?
Leukoencephalopathy
Spongiform brain tissue with holes
Progresses to ataxia, apathy, akathisia, inability to speak or move
Appears like metal toxicity
How is heroin injected?
Mixed with some water on a spoon, acid or heat might help dissolve, drawn up through a cotton ball to remove particulates
Why does injecting heroin leave track marks?
Damage to vessels by the needle
Uneven blood flow, thrombosis, clots form
Vessels collapse, need to find a new one
Where are opioids metabolized?
Brain
Liver
How are opioids excreted?
Kidneys
Feces
What are the pharmacokinetics of heroin?
Faster distribution to the brain = higher potency
May be snorted
Metabolized to morphine in the brain
Two intermediates = 3-MAM and 6-MAM
6-MAM binds MOR but 3-MAM does not
6-MAM is not naturally occurring
What are the psychological effects of acute opioid use?
Euphoria, well-being, tranquillity
Mental clouding, impaired judgement, decreased attention and memory
What are the brain effects of acute opioid use?
Reduced pain
Inhibited cough and slowed respiration
Increased sedation
Constricted pupils
What are the cardiovascular effects of acute opioid use?
Dilated blood vessels and lowered blood pressure
What are the effects of acute opioid use on the skin?
Lowered body temp
Flushed skin
Itching
What are the effects of acute opioid use on muscles?
Muscle relaxation
What are the effects of acute opioid use on the renal system?
Decreased urination
What are the effects of acute opioid use on the GI tract?
Decreased GI movements and secretions
Constipation
What are the effects of acute opioid use on the reproductive system?
Decreased testosterone and estrogen
Lowered sperm production
Diminished libido
How does acute opioid use affect the medulla?
Lowers BP
Hypotension, bronchoconstriction, itching from histamine release
Why do the pupils constrict with opioid use?
mu/kappa receptors in oculomotor nucleus
What is neonatal abstinence syndrome?
Babies are irritable, vomit, diarrhea, seizures, in respiratory distress due to withdrawal
How is NAS treated?
Physical contact reduces hospital time