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Chapter 1-4

PSYC3030 Chapter 1-4: Psychopharm final exam.docx

Course Code
PSYC 3030
Boyer Winters

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Chapter #11: Opioids
Narcotic Analgesics
-Opioid drugs all belong to narcotic analgesics
Reduce pain without producing unconsciousness, but produce a sense of relaxation and
sleep and at high doses, coma and death
Best painkillers
Produce a sense of well being and euphoria
Cont use leads to tolerance and sometime dependence
Anesthetics reduce all sensations by depressing CNS and produce unconsciousness
The opium poppy has a long history of use
-Opium is extract of the poppy plant and is source of drugs known as opiate or opioids
-Been used as both medicine and for rec purpose
-Illegal to provide opioids for addicted individuals or rec use
Minor differences in molecular structure determine behavioural effects
-Principal active ingredient was called morphine
-Also contains codeine, thebaine, narcotine and others
-The natural opiate codeine is identical in structure to morphine except for substtution of a
methoxy for a hydroxyl group
This produces less analgesic effect and fewer side effects than morphine but still a potent
cough suppressant
Today we know that the pharm effects of morphine and heroin are identical because heroin
is converted to morphine in the brain. Heroin is 2-4 times more potent when injected and
faster acting since the change makes the drug more lipid soluble. When taken orally, both
drugs are equal in potency
-Some of the modifications to morphines structure produce partial agonists, which are drugs
that bind readily to the receptors but produce less biological effect
So when given along they produce partial opioid effects, but when given along with an
opioid that has higher effectiveness, they compete for the receptor and reduce the action of
the more effective drug
-Other modications of morphine produce pure antagonists like naloxone and nalorphine;
produce no pharmacological activity of their own

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Prevent or reverse effect
IV admin naloxone can revive an unconscious person in seconds; can reverse all the opiods
effects and save those after opioid OD
-Prototypic partial agonist is pentazocine, others are nalbuphine and buprenorphine
As analgesis are less potent than morphine and don’t case sig. resp depression or
constipation and have reduced risk for dependence
-Some narcotic drugs are natural derivatives, others are semisynthetic since they have chemical
modifications (i.e. hydromorphone and heroin). Others are entirely synthesis
Bioavailability predicts both physiological and behavioural effects
-If morphine is admin for medical purposes, its usually injected IM or given orally
-Rec users often smoke opium for its rapid absp. From the lungs
-Only small fraction of morphine capable of crossing the BBB to act on opioid receptors in the
-Opioid dist. Fairly uniform in rest of body and drug easily pass the placental barrier, exposing
unborn child
Infants are readily stabilized with low doses of opioids to prevent abstinence signs and the
dose is gradually reduced
Most of opioid metabolites are excreted in the urine within 24 hrs after metabolism
Opioids have their most important effects on the CNS and on the GI tract
-The multiple effects of morphine and other opioids on CNS are dose-related and also related to
the rate of absorption
-At low to mod doses, pain is relieved, respiration is somewhat depressed and pupils are
The principal subjective effects are drowsiness, decreased sensitivity to the environment
and impaired ability to concentrate, followed by a dreamy sleep
-Opioids have actions in limbic system, some suggest they relieve psychological pain, incl.
anxiety, feelings of inadequacy and hostility lead to increased drug use
-Morphine also suppresses cough reflex in dose-dependent manner and have actions on
hypothalamus that lead to decreased appetite, drop in body temp, reduced sex drive and a
variety of hormonal changes
-At higher doses (i.e. admin inhaled or I.V.) the person experiences state of elation of euphoria
which is referred to as the kick, bang or rush

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To achieve needs very rapid penetration into the brain
Euphoric effect doesn’t always accompany IV admin
-Nausea and vomiting that may accompany low doses of morphine is increased with higher
Related to morphines effect on the CTZ
Sometimes the nausea is a “good sick” since its closely associated with euphoria
-At highest doses, the opioids sedative effects become stronger and may lead to
Body temp and BP fall
Pupils constricted and are sign of opioid OD in a comatse patient
Resp impaired due to action on brainstems resp center. Resp failure is the ultimate cause of
death in OD
-Apart from CNS, effects of morphine are greatest on GI tract
Opium was used for relief of diarrhea and dysentery
Still impt for causing constipation and stopping fluid loss associated with diarrhea
-More modernized drugs utilizes modified opioid molecules like loperimide, whch cannot cross
Major advt is that it slows GI function but dosent have effect on CNS
Even when used for pain mgmt., constipation is common side effect
Opioid Receptors and Endogenous Neuropeptides
-Opioid drugs produce biobehavioural effects by binding to neuronal receptors
Receptor binding studies identified and localized opioid receptors
-Classic binding curve, as the amount of radioactive opioid (ant naloxone) is increased, binding
also increases an gradually tapers off until the receptors are fully occupied
-A finite number of receptors exist ina given amount of tissue
This saturation wouldn’t occur if the radioligand was sticky and attached randomly to
many cellular materials
-Looking at the concentrations used in the assay makes it clear that the binding sites have a
high affinity for the opioids
-Third, the binding was shown to be reversible, with a time course that matches the loss of
physiological effectiveness
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