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42 Cards in this Set

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504-2 OPIOD ANALGESICS
504-2 OPIOD ANALGESICS
Narcotic
Drugs that cause dependence
Indications for use of opioids?
1. relief of intense pain
2. relief of cough
3. treatment of diarrhea
4. Tx of acute pulmonary edema
What is the mechanism of action for opioids?
Interact with endogenous receptors called Opioid Receptors.
Opioid receptors are activated by what?
Endogenous opioid peptides

Primarily localized to brain and spinal cord regions.
What are some examples of endogenous opioid peptides?
1. enkephalins
2. endorphins
3. dynorphins
What are the functions of opioid peptides?
1. modulate pain, stress, dependence, and eating.
2. they are neurotransmitters (NTs)
What are some examples of opioid receptors?
1. MU (OP3/MOP)
2. Delta (OP1/DOP)
3. Kappa (OP2/KOP)
What is the function of Mu receptors?
Mediate opioid induced analgesia and positive reinforcement, respiratory depressio, miosis, decreased GI motility, and neuroendocrine effects.
What affinity does Mu receptors have for?
High affinity for enkephalins, Beta endorphin, and morphine.

Endorphins > enkephalins > dynorphins
What affinity does delta receptors have for?
High affinity for enkephalins and beta endorphins.

enkephalins > endorphins and dynorphins
Functions of delta receptors?
Antiociception, motor integration, and cognitive function.
What affinity does Kappa receptors have for?
High affinity for dynorphin

dynorphins > endorphins and enkephalins
What is the function of kappa receptors?
Regulation of food intake, temp control, GI motility, pain perception, and neuroendocrine function.
Opioid receptors are coupled primarily to what type of proteins?
Inhibitory types of G proteins
Ascending pain transmission pathways are in what tract?
This pathway mediates phasic pain and is located in the fast conducting lateral spinothalamic tract.
What is phasic pain and how is it transmitted?
Produced by noxious stimulus.

Transmitted through the fast conducting A-gamma fibers.
How is tonic pain produced and transmitted?
Produced by tissue damage in the skin or viscera.

Transmitted through unmyelinated, slow conducting C fibers through the dorsal horn.
What are the major ascending pathways for tonic pain?
Multisynaptic pathways of the spinoreticular and paleospinothalamic tracts.
Descending pain modulatory pathways
Project from cortex to midbrain periaqueductal gray. (PAG)

Then it makes connections to neurons extending into the rostroventral region of the medulla (RVM).
What role does the descending pathway play?
Inhibitory role on the ascending pain transmission neurons.
Where are the opioid receptors found?
On primary afferents and spinal cord pain transmission neurons.

Also present in the descending pain modulatory pathways, including PAG and RVM.

Also localized to brain stem areas that are involved in controlling respiration, cough, nausea, vomitting, BP, stomach secretion, and pupillary diameter.

Also in Hypothalamus

Also in GI tract
Function of opioids?
Produce a direct analgesic effect on the spinal cord by inhibiting the release of excitatory NT and by inhibiting the dorsal horn pain transmission neurons.
Effects of opioid drugs on the CNS?
1. analgesia
2. euphoria or dysphoria
3. sedation
4. resp depression
5. cough suppression
6. miosis: constriction of pupils.
7. emesis
Miosis
A diagnostic sign for opioid overdose.
Effects on other body systems:
1. CV
2. GI
3. Neuro
4. Dermal
1. CV: hypotension and vasodilation
2. GI: constipation (opioids relieve diarrhea).
3. Neuro: ADH and prolactin stimulated to be released. LH inhibited.
4. Dermal: flushing , pruritis, urticaria
5. GI: urinary retention, prolongation of labor.
Morphine duration
4-6 hrs
Active metabolite of morphine?
Morphine-6-glucuronide
Heroin
A scheduled I controlled substance

Acetylation makes it more lipid soluble and fast acting.
Methadone duration
15-20 hrs.
What is methadone used for?
Detoxification and controlled withdrawal of addicts from heroin and morphine.
Meperidine duration
2-4 hrs

Used as an obstetric or postsurgical analgesic.
Fentanyl
Rapid onset and short duration (15-30 mins)
The strong agonists:
1. morphine (major component)
2. heroin
3. methadone
4. meperidine
5. fentanyl
Moderate agonists
Codeine
Codeine
Can be metabolized to morphine, but requires activity.

For mild to moderate pain

Used in combination with aspirin and acetaminophen.

Alleviate cough
Mixed agonist-antagonists
1. pentazocine
2. buprenorphine
3. naloxone
4. naltrexone

Behave as an agonist as well as antagonist depending the receptor subtype.
Pentazocine
Kappa receptor agonist

Precipitates a withdrawal syndrome in a morphine abuser.
Buprenorphine
Potent and long-acting partial agonist at the Mu-receptor.

Slow dissociation from Mu receptor makes it resistant to Naloxone reversal.

Effective Tx for cocaine addiction and heroin abusers.
Opioid antagonist
Naloxone

Naltrexone
Naloxone
Competitive antagonist

Reversal of opioid overdose
Naltrexone
Used as a "maintenance" drug for addicts in Tx programs.

Tx chronic alcoholics by decreasing craving for alcohol.