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Neuro Unit 2 > Opioid Analgesics > Flashcards

Opioid Analgesics Flashcards

1
Q

What is the source of opioids?

A

Plants: The opium poppy
Animals: endogenously occurring

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2
Q

What are the endogenous opiods?

A

Enkephalins- short peptides. Act as neuromodulators at synapses. Derived from pro-enkephalin
Endorphins: Hormones that can act more systemically. Derived from proopiomelanocortin. Beta endorphin is the most active endorphin.
Dynorphin: Derived from prodynorphin. dynorphin A is most biologically active Kappa selective
Endomorphines- mu receptor selective
(Nociceptins- bind to opioid-like receptors and regulate pain transmission)

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3
Q

What antagonizes the effects of enkephalin, endorphin, and dynorphins?

A

Naloxone

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4
Q

Where do opioids bind?

A

Exogenous: transmembrane domains
Endogenous: transmembrane and extracellular

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5
Q

What are the different types of opioid receptors?

A

mu, delta, kappa, others

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6
Q

What is the signaling mechanism of the opioid receptor.?

A 
G-protein coupling
decrease neuronal excitability. 
Inhibition of pre-synaptic Ca channel
activation of potassium channel
inhibition of cAMP synthesis
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7
Q

What is the mechanism of inhibition in pain pathways?

A
  1. Inhibit neurotransmitter release in the presynaptic terminal in spinal cord/ascending pathway. Also inhibits post-synaptically through opening of K channels.
  2. Activation of descending pathway. Mediated by serotonin and norepinephrine.
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8
Q

What is the mechanism of inhibition in pain pathways?

A
  1. Inhibit neurotransmitter release in the presynaptic terminal in spinal cord/ascending pathway. Also inhibits post-synaptically through opening of K channels.
  2. Activation of descending pathway. Mediated by serotonin and norepinephrine, as well as Enkephalin.
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9
Q

What type of pain are opioids effective in treating?

A

Nociceptive pain, not neuropathic pain

Relieve dull, constant pain (2nd pain), not sharp pain (1st pain)

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10
Q

What are the typical uses of opioids?

A 
Pain with malignancy
painful diagnostic procedures
post-operative pain
obstetrical anesthesia
patient-controlled analgesia (PCA)
cough (lower doses) : separable from analgesic actions
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11
Q

What are the behavioral effects of opioid drugs?

A

Euphoria (mu receptors- VTA, NAcc)
Dysphoria- hallucinations (Kappa receptors)- rare
Sedation, lethargy, confusion- very common, overall CNS depression

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12
Q

What are the behavioral effects of opioid drugs?

A

Euphoria (mu receptors- VTA, NAcc)
Dysphoria- hallucinations (Kappa receptors)- rare
Sedation, lethargy, confusion- very common, overall CNS depression
Behavioral Excitation- sign of acute toxicity

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13
Q

What is the most dangerous side effect of opioids?

A

Respiratory depression- primary cause of death.
Decreased sensitivity to blood CO2 levels.
Opioids contraindicated in case of suspected head injury, because of vasodilation from increased CO2

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14
Q

What are the effects of opioids on the brainstem?

A 
Nausea and vomiting??????????????
Cough suppression: doses lower than necessary for analgesia and respiratory depression- some don't even have analgesic effects
Pupillary constriction (miosis)- excitation of edinger-westphal nucleus. "pinpoint pupils"
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15
Q

What are the effects of opioids on GI system?

A

Constipation- very little tolerance develops
Therapeutic- anti-diarrheal like loperimide (imodium)
Can also use antagonists (that don’t get absorbed systemically) to treat opioid induced constipation

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16
Q

What are the effects of opioids on histamine?

A

Can cause histamine release from mast cells and basophils- can lead to itching, urticaria, local vasodilation, headache. Peripheral vasodilation can lead to reduced blood pressure.

17
Q

What are the effects of opioids on CV system?

A

Decrease in cardiac work load
Inhibition of baroreceptor reflex
Use opioids with caution if pt is hypovolemic
Therapeutic- myocardial infarction to control pain and decrease cardiac load. Also, pulmonary edema associated with cardiac dysfunction

18
Q

What are the contraindications to opioid use?

A 
Respiratory depression of any cause
Suspected head injury
Hypotension
Shock (because endogenous opioid system is involved in the shock response)
Impaired hepatic function
Histamine Release
Hypothyroidism
19
Q

How are opioids absorbed?

A

?

20
Q

How are opioids distributed?

A

?

21
Q

How are opioids Metabolized?

A

?

22
Q

Discuss morphine

A

Widely used to relieve severe pain

23
Q

Discuss heroin

A

rapid onset- not approved for medicinal use

24
Q

Discuss codeine

A

Metabolized to morphine. Often combined with tylenol or aspirin. Less potent than morphine- toxicity at high doses. High oral bioavailability.

25
Q

Discuss Oxycodone

A

Good oral bioavailability

26
Q

Discuss Hydrocodone

A

antitussive, weak analgesic, similar to codeine

27
Q

Discuss Tramadol

A

acts at mu receptors. ????????

28
Q

Discuss Meperidine

A

Used to treat severe pain. faster onset and offset than morphine. Decreased side effects and slower development of tolerance, but toxic metabolites
Loperimide??????????
Fentanyl????????????

29
Q

Discuss Methadone

A

?

30
Q

Discuss the partial opioid agonists

A

Buprenorphine: Could precipitate withdrawal symptoms.
Pentazocine:???????????

31
Q

Discuss the opioid antagonists

A

Naloxone: short acting. poor oral bioavailability
Naltrexone: long duration, orally active, tx of alcoholism
Alvimopam: Insoluble, not absorbed from GI tract, acts locally

32
Q

What factors are involved in the development of opioid tolerance?

A

Frequency of drug administration
Dose at which the drug was administered
Duration of drug use
Tolerance linked to opioid receptor desensitization
Tolerance reverses following withdrawal
Tolerance can generalize to similar drugs

33
Q

What factors are involved in the development of opioid Dependence?

A

Physical: continued use to maintain a normal physiological state
-mild with short term use
-more pronounced in pts with long term use
Psychological: continued desire or craving for a drug

Due to adaptation in neural circuits involving other neurotransmitter systems.

34
Q

What are symptoms of withdrawal from opioids?

A

Dilated pupils, insomnia, restlessess, yawning, rhinorrhea, sweating, diarrhea, nausea, cramps, chills
Can be precipitated by switch to partial agonists
Can prevent with opioid maintenance therapy
Clonidine can be used to treat withdrawal symptoms caused by sympathetic overflow.

Neuro Unit 2 (21 decks)

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