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Chapter 9

PHAR 100 Chapter Notes - Chapter 9: Opioid Overdose, Gastrointestinal Physiology, Narcotic Control Act

Pharmacology and Toxicology
Course Code
PHAR 100
Bill Racz

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Lesson B.4 Narcotic Analgesics (Opiates, Opioids)
- Define the terms opioid endorphins and opiate
- State the role of opioid receptors in mediating opioid-induced analgesia
- List the classification of the opiates and give an example of each class
- State the therapeutic uses for opioid drugs and treatment for abuse
- State the pharmacological effects of the opiods
- Describe dependence and abuse to morphine and heroin
Opium crude resinous exudate of the opium poppy, Papaver somniferum
- Used extensively for social and medicinal purposes to produce euphoria, analgesia, sleep and relief
from diarrhea (300 B.C. to 1800 A.D)
- Contains 20 different chemical compounds
- Morphine and codeine are analgesic (pain-relieving) drugs; making up approx. 10-0.5%
- Morphine was isolated in the 1800s
- Opioid refers to any natural or synthetic substance which exerts actions on the body that are
similar to those induced by morphine. These are antagonized (blocked) by the drug naloxone
o Opiates narcotics (analgesic agents)
o Substances structurally related to morphine
o Synthetic drugs with structures different from that of morphine
o Endogenous brain peptides that exert analgesic actiodns (opioid peptides: enkephalins and
- 1970’s – receptor sites for opioid molecules were found in the brain of humans/animals
- 1975 endogenous substances (peptides, collectively known as endorphins) were isolated, these
interacted with opioid receptors
- At least 3 families of known endorphins: enkephalins, dynorphins and β-endorphins
o These act as neurotransmitters and neuromodulators affecting the perception of pain and
the elicited response to it, they may also influence moods associated with the reward
pathways in the brain
- Opioid receptors include:
o μ receptors located in the brain and spinal cord, mediate analgesia; involved in the
compulsive abuse behaviour demonstrated by opiate users and mediate morphine mediated
depression of respiration in the brain stem
o κ receptors involved in analgesia, dysphoria and miosis (pin-point pupils), mixed
agonist/antagonists, dynorphin endogenous ligands act predominantly however some
endorphin activity is present; pentazocine acts predominantly on these receptors
o δ receptors involve endogenous ligands (enkephalins), they are involved in analgesia
and modulate the emotional response to opioids
- Opioid receptors are located in the peripheral and central nervous system: brain, spinal cord,
gastrointestinal tract
Classification of Opiates/Opioids
- Agonists:
o Illicit a full response
o Natural: morphine and codeine
o Semi-synthetic: heroin
o Synthetic: meperidine and methadone
- Mixed Agonists/Antagonists:
o Pentazocine illicit a response when given alone, but can block part of the response to
morphine when given together
- Antagonists:
o Block the response to morphine, heroin and other opiates at the respective receptor
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