Opioids

Question 1

Opiates vs. Opioids

Answer 1

Opiates are drugs derived from the juice of the opium poppy like morphine and codeine

Opioids can be natural or synthetic compounds with morphine-like actions.

Question 2

Types of opioid peptides

Answer 2

Enkephalins
Endorphins
Dynorphins

Question 3

Mu Receptors (OP3/MOP)

Answer 3

High affinity for enkephalins, B-endophin, and morphine. endorphins > enkephalins > dynorphins

Mediate opioid induced analgesia and positive reinforcement, respiratory depression, miosis, decreased GI motility, and neuroendocrine effects.

Question 4

Delta Receptors (OP1/DOP)

Answer 4

High affinity for enkephalins and B-endophin.
enkephalins > endorphins and dynorphins

Antinociception, motor integration, and cognitive function

Question 5

Kappa Receptors (OP2/KOP)

Answer 5

High affinity for Dynorphin
dynorphins > > endorphins and enkephalins

Regulation of food intake, temperature control, GI motility, pain perception, and neuroendocrine function.

Question 6

Pain Pathways

Answer 6

Ascending pain transmission:
Afferent nociception to dorsal horn -> parabrachial nuclei in the Medulla/Pons -> Ventral caudal thalamus -> Cortex

Descending pain modulatory pathways:
Cortex -> Midbrain -> Medulla/Pons -> Dorsal horn

Question 7

Conduction from Periphery to Spinal Cord

Answer 7

Phasic Pain:
Aa and B large diameter myelinated “light touch” axons sens sharp immediate pain

Tonic Pain:
Adelta lightly myelinated medium diameter followed by C unmyelinated small diameter fibers

Send transmission to the somatosensory cortex

Question 8

Effect of Opioids on the CNS

Answer 8

Analgesia
Euphoria or Dysphoria
Sedation
Respiratory Depression
Cough suppression
Miosis
Emesis

Question 9

Effect of Opioids on the body

Answer 9

Hypotension and vasodilation
Constipation; relief of diarrhea
Urinary retention
Decrease in uterine contractions
Stimulation of release of ADH and prolactin
Inhibition of release of Luteinizing Hormone
Skin flushing, Pruritus, Urticaria

Question 10

Tolerance

Answer 10

Decreased responsiveness to a drug

No tolerance to miotic and constipating actions

Cross tolerance among opioid analgesics

Question 11

Dependence

Answer 11

An adaptive state that requires the presence of a drug to maintain cellular homeostasis. Discontinuation of said drug will lead to withdrawal syndrome.

Question 12

Morphine***

Answer 12

Strong Opioid Agonist

High affinity for Mu receptors
Treatment of severe pain

Prototypical
Major active ingredient in opium (10%)
4-6 hour duration of action
Active metabolite: morphine-6-glucuronide

Question 13

Methadone (Dolophine)***

Answer 13

Strong Opioid Agonist

Orally effective
Long duration of action (15-20 hours)
Used for detoxification and controlled withdrawal from heroin and morphine

Question 14

Meperidine (Demerol)

Answer 14

Strong Opioid Agonist

Less potent than morphine
Short duration of action (2-4 hours)
An obstetric or postsurgical analgesic

Question 15

Fentanyl (Sublimaze)

Answer 15

Strong Opioid Agonist

80 times more potent than morphine
Rapid onset (< 5 minutes)
Very short duration (15 - 30 minutes)
Adjunct to general anesthesia

Question 16

Codeine***

Answer 16

Moderate Opioid Agonist

0.5% the concentration of opium
Metabolized to morphine for analgesic activity
Added to aspirin and acetaminophen for moderate pain
Included in many cough syrups for relief of cough

Question 17

Tramadol (Ralivia)

Answer 17

Moderate Opioid Agonist

Synthetic analog of codeine
Moderate Mu receptor agonist and a weak inhibitor of norepinephrine and serotonin reuptake
Treatment of moderate pain
Alternative for patients who may not tolerate NSAIDs
Lower abuse potential

Question 18

Definition of Mixed Agonist-Antagonist

Answer 18

A drug that exhibits partial agonistic or antagonistic activity at Mu receptors and shows agonistic or antagonistic activity at Kappa receptors.

Advantages include a ceiling to respiratory depression and lower abuse potential

Disadvantages include dysphoria at high doses, and difficult to antagonize

Question 19

Definition of a Partial Agonist

Answer 19

Drug that can only produce a submaximal response
Have agonistic action in the absence of full agonist
Have antagonistic action in the presence of full agonist

Question 20

Pentazocine (Talwin)***

Answer 20

Mixed Opioid Agonist-Antagonist

Kappa receptor agonist with weak Mu receptor antagonist activity
Orally administer for treating moderate to severe pain
Parenteral formulation as a preanesthetic medication
Causes withdrawal syndrome in morphine abusers

Question 21

Buprenorphine (Buprenex)***

Answer 21

Mixed Opioid Agonist-Antagonist

Partial agonist at Mu receptors and an antagonist at Kappa receptors
Resistant to Naloxone reversal
Used to manage cocaine addiction and heroin abuse

Question 22

Buprenorphine (Buprenex)

Answer 22

Mixed Opioid Agonist-Antagonist

Partial agonist at Mu receptors and an antagonist at Kappa receptors
Resistant to Naloxone reversal
Used to manage cocaine addiction and heroin abuse

Question 23

Naloxone (Narcan)***

Answer 23

Opioid Antagonist

Competitive antagonist (half life of 1-2 hrs)
No obvious effects on normal people
Antagonist-precipitated withdrawal
Intravenous injection for treating opioid overdose

Question 24

Naltrexone (ReVia)***

Answer 24

Opioid Antagonist

A competitive antagonist (half life of 10 hrs)
Antagonist-Precipitated withdrawal
Maintenance drug for addicts
Also used in treatment for alcoholics