Chapter 11: Opioids Flashcards
two main traits of a narcotic analgesic
makes you sleepy and produces analgesia (less pain)
main plant as opiate source
poppy Papaver somniferum
2 main active ingredients in opium
1) morphine (makes up 10%)
2) codeine (makes up 0.5%)
is heroin a natural opioid
no, it is synthetic, made by adding two acetyl groups to morphine
is morphine more lipid soluble than heroin
no, heroin is more lipid soluble than morphine, allowing it to get to the brain a lot faster.
medical name for heroin
diacetyl morphine
another name of a paramorphine that is used in oxycodone
thebaine
main incredients of percocet
thebaine (oxycodone) and acetaminophen
oxycontin is just concentrated ____
concentrated oxycodone.
what is percodan
oxycodone mixed with aspirin
is demerol synthetic or natural. comment on its half life
synthetic, shorter acting
synthetic opioid used as a maintenance drug for heroine addicts
methadone
what drug causes “frozen addict” symptoms? Why?
the designer drug MPTP, created when trying to make meperidine. MPTP destoys the SUBSTNATIA NIGRA and EXTRAPYRAMEDAL MOTOR SYSTEM, which provides dopamine stimulation to the basal ganglia. This results in parkinson-like symptoms.
why was heroin originally created?
tried to create a “safer” drug to morphine, one with less respiratory depressive effects and less likelihood to get addicted
T/F: Heroin is banned for medical use in Britain
False. Heroin can be used for medical use in Britain, but it is illegal in all forms in the states and Canada
who founded heroin?
Henrich Dreser
why was heroin more appealing for morphine users in the early 1900s?
because it didn’t cause as much nausea and the effects were more stronger.
is morphine acidic or basic, does this mean it can be taken in pill form?
basic, pka of 8. not as effective in pill form because the molecules are ionized and thus NOT LIPID SOLUBLE, there is also significant first pass metabolism
bioavailability of morphine versus methadone after first pass metabolism via ingestion
morphine gets subjected to significants amounts of first pass metabolism if it is injested orally. Bioavailabiltiy of only 15%. On the other hand, methadone hass 80-90% bioavailability after first pass metabolism.
benefit of taking an opioid orally despite large first pass metabolism and slow absorption because of basic pka?
the slow absorption allows long-time affect due to constant blood levels of morphine. good for clinical analgesic-use
competitive opioid receptor antagonists.
nalorphine and naloxone
T/F: heroin, but not morphine, can be inhaled through the nose
true. heroine is more lipid soluble and can pass through the mucus membranes better than morphine.
organs in which opioids are concentrated in
the lungs, liver, spleen and some blood proteins. NOT THE BRAIN
T/F: opioids can pass through the placental barrier
true.
T/F: opoids are slow getting through the blood brain barrier. Why or why not? exception to this rule?
slow getting through the blood-brain barrier because they have poor lipid solubility. Heroin can pass quickly because it has higher lipid solubility than morphine
What is heroin metabolized to in the brain? is it heroin or its metabolites that produce the intended effects?
heroin is INACTIVE, but it is metabolized in the body to MORPHINE, which creates effects. heroin thus effectively allows morphine to cross the lipid membranes faster.
what allows the brain to keep opoid level at a lower concentration than the rest of the body?
the brain has an active transport mechanism that removes the opoid from the brain.
where in the brain are opioids relatively concentrated that allows for decreased pain sensation
opioids are affecting the PERIAQUADUCTAL GRAY, allowing for analgesic effects. Also concentrated in the basal ganglia (VTA) and amygdala, allowing better mood state and reinforcing effects (affecting pain tolerance)
T/F: opoid antagonists such as naloxone enter the brain quicker than morphine
true
how are most opioids excreted?
through the urine and feces. 10% of morphine is extcreted as morphine, the rest as metabolized products..
why does methadone have a much longer half life than other opioids such as meperidine (demerol)?
because methadone becomes bound to BLOOD PROTEINS which are not available for breakdown. the methadone that does get excreted is excreted as methadone, it is not metabolized into something prior to being peed out.
Why does antagonist naloxone have a shorter half life?
because it is lipid soluble and the drug gets rapidly redistributed into body fat. Thus, if you are trying to use this drug as a opioid overdose, you might need to administer it repeatedly.
what are the endogenous ligands that bind to the body’s opioid receptors
endorphines.
how does lipid solubility contribute to addiction?
the faster the drug can cross a membrane (increase solubiltiy) the faster and stronger the positive affects are. therefore, it has higher reinforcing effects because the affects are more instantaneous
rank these with highest to lower potency: heroin, fentanyl, morphine
fentanyl>heroin> morphine
fentanyl is 200 times stonger than morphine
heroin is 10 times stronger than morphine
T/F opioid receptors are ionotropic receptors
false, they are metabotropic
what kind of receptor are opioid receptors
metaboropic receptors
what kind of proteins are opioid receptors coupled to?
INHIBITORY G-protein receptors which release second messengers.
how do G proteins activate and inhibitory response?
stimulation of G proteins activates the OPENING of K+ channels, cause K+ TO LEAVE THE CELL, making the cell MORE NEGATIVE.
the G proteins also inhibit CALCIUM, meaning that the prevent the cell from firing. Ca2+ CANNOT ENTER THE CELL, it makes the cell more negative.
what does activation of the opioid receptors do to the presynaptic cell? the post synaptic cell?
presynaptic: they inhibit the relase of neurotransmitters because Ca2+ ion channels are blocked
post synaptic: they open the K+ ion channels, making the cell extremely hyperpolarized (more negative) and thus transmitters that do happen to bind to the postsynaptic side do not provide any effect.
because the opioid receptors operate on both pre and post synaptic cells, what does this make the opioids?
opioid drugs themselves are thus INHIBITORY neurotransmitters (open K+ channesl) and INHIBITORY neromodulators (block ca2+ channels)
what secondary messenger is inhibited by opioid receptor activation?
cAMP
how does opioid receptor stimulation result in changing gene expression?
because the receptor-ligand complex can move inside the neuron and react with KINASES, altering the activity of TRANSCRIPTION, changing the expression of genes in the cell nucleus.
When a drug has agonistic effects on two or more receptor types
mixed agonist drug.
activation of all types of opioid receptors has the___ effect on all cells, but the ____ of the cell determines what effect the opioid will have in the brain and on behavior.
activation of all types of opioid receptors has the SAME effect on all cells, but the LOCATION of the cell determines what effect the opioid will have in the brain and on behavior.
where is the mu receptor primarily located?
throughout the limbic system (hippocampus and amgydala), throughout the locus coeruleus and the VTA.
this receptor is primarily known for its reinforcing effects when stimulated
where is the delta receptor primarily located
also in the limbic system but IT DOES NOT OVERLAP WIth thE MU RECEPTOR
Where is the kappa receptor primarily located?
in the Nucleus accumbens, the VTA and hypothealamus, some in the thalamus.
known for producing aversive effects when stimulated.
generally, the effects of a drug are stronger when its binding affinity to the opioid recpetor is ___
WEAK. thats why morphine has a weak binding affinity to the mu receptor and is potent, but naloxone has a high bindign affinity to the receptor and is less potent.
if a drug with a high binding affinity is mixed with a drug with a low opiate receptr affinity, which would bind? which would act as an antagonist to the other?
the drug with the high bindign affinity (nalorphine) will bind to the receptor stronger than the one with the low affinity (morphine). thus, it will push morphine out of the way and bind, and the person would see the less-severe effects of the naloxone (stronger binding affinity=less effects)
the naloxone thus acts as an ANTAGONIST to morphine because it blocks morphine from working. this is why naloxone is called a PARTIAL AGONIST because it binds to something AND CAUSE ITS OWN EFFECTS, while blocking something else.
partial antagonists-agonists will terminate the activity of more potent agonist drugs and at the same time have a milder effects of their own.