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Opoid Analgesics Flashcards

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1
Q

Why is the class of “Opioids” called this name?

A

They are an entire class of morphine like substances, specifically they are alkaloid of the opium poppy.

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2
Q

What is the difference between spinal analgesia to supraspinal analgesia?

A

Spinal analgesia raises the pain threshold at the spinal cord level, but the supraspinal alters the brain’s perception of pain.

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3
Q

What are the 3 endogenous opioid peptides in humans?

A

Endorphins, enkephalins and dynorphans.

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4
Q

What is the function of the mu receptor subtype? Which opioid peptides hit this type of receptor?

A

Supraspinal and spinal analgesia: causes sedation, euphoria, inhibition of respiration, slowed GI transit (constipation), and modulation of hormone and neurotransmitter release.
Endorphins > enkephalins > dynorphins, in that order of affinity for the receptor.

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5
Q

What is the function of the delta opioid receptor? What is the receptor affinity to opioid peptides?

A

Both supraspinal and spinal analgesia, and modulation of hormone and neurotransmitter release. Enkephalins > endorphins and dynorphins.

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6
Q

What is the function of the kappa opioid receptor and what is its receptor affinity?

A

Also analgesia of supraspinal/spinal levels, psychotomimetic effects (dysphoria, opposite of euphoria) and slowed GI transit. Dynorphins has a high affinity to this receptor, endorphins and enkephalins much less so.

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7
Q

First pass metabolism of opioids? Metabolism and excretion?

A

Extremely high. Metabolites conjugate with glucoronic acid, gets polarized and renally excreted, (small amounts undergo enterohepatic circulation). Drugs would accumulate with renal problems.

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8
Q

What is a major side effect of patients receiving drugs like morphine and meperidine, which have neuroexcitatory active metabolites?

A

Seizures.

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9
Q

What is the MOA of morphine like opioid agonists?

A

2 pronged effect: First, the upon activation of the opioid receptor, it will decrease adenyl cyclase activity and will block the opening of the Ca channels, thus the pain neurotransmitters are not released. Secondly, it will open the K+ channels and thereby induce hyperpolarization in the cell.

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10
Q

What kind of receptors are the opioid receptors?

A

They are G sub i proteins (inhibitory proteins).

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11
Q

Besides the opioid receptors, what else blocks the release of the pain neurotransmitters?

A

Alpha 2 receptors.

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12
Q

What is the neurotransmitter of the descending interneuron pathway and what does this receptor do?

A

Descending interneuron is GABA-nergic, when we do not experience pain this interneuron would inhibit the descending pathway, GABA inhibits the descending pathway.

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13
Q

What is the function of opioids on the descending interneuron pathway?

A

It will disinhibit the GABA, ergo activate the GABA, and since GABA is an inhibitory neurotransmitter this will inhibit the descending pathway and thus no pain from the CNS.

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14
Q

How do opioids induce tolerance in patients? What effects of opioids do people NOT develop resistance to?

A

Receptor desensitization, internalization, resensitization and downregulation. However, miosis, constipation and convulsant effects not going to get tolerance.

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15
Q

What are signs/symptoms of physical dependance?

A

Rhinorrhea, lacrimation, yawning, chills, piloerection, hyperventillation, hyperthermia, mydriasis, muscular aches, vomitting, diarrhea, anxiety and hostility.

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16
Q

What are the CNS effects of morphine like opioids?

A

Analgesia, euphoria, sedation, respiratory depression, cough suppression, miosis, truncal rigidity, n/v, altered temperature regulation.

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17
Q

What are the neuroendocrine effects of morphine like opioids?

A

Releases ADH, prolactin and somatotropin. Inhibits the release of LH.

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18
Q

What are the peripheral (non CNS related) effects of morphine like opioids?

A

Bradycardia and hypotension in susceptable pt’s, constipation, biliary and urinary colic, urinary retention, pruritis and utcaria.

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19
Q

What are the immune system effects of opioids?

A

Can either mess with or improve the immune system depending on context.

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20
Q

Why do opioids cause pruritis (itching) and urticaria (hives)?

A

NOT an immune HS reaction (in which the IgE would bind to mast cells). Instead it is the opioid agonists binding to the mast cells which causes mast cell degranulation and release of histamine. Histamine can also induce the hypotension, which is another side effect of Opioid agonists.

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21
Q

What are some Tx uses of opioid agonists?

A

Tx of severe pain acute or chronic (morphine is always given to terminally ill patients), adjunct to anasthesia, cough suppression, diarrhea (because opioids slow GI motility), M.I. (IV morphine is administered, reduce pain reduce sympathetic tone, etc), Dyspnea (but ONLY with patients with pulmonary edema with LV failure), and post op shivering (Meperidine).

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22
Q

If Opioids cause respiratory depression why is it used to treat patients with pulmonary edema with LVF that is suffering from dyspnea?

A

Similar to MI, IV morphine will decrease anxiety, decrease venous tone (pre-load), decrease peripheral vascular resistance (afterload), thus decrease work of the heart (decreased O2 consumption) and thus relieve ischemia and reduce pain.

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23
Q

State all the adverse effects of Opioid agonists, regarding CNS, lungs, temperature homeostasis, bladder, uterus, skin, gall bladder, eyes, and constitutional health.

A

CNS behavior changes such as hyperactivity, restlessness, dysphoria, etc, as well as seizures in high doses, respiratory depression (dose related and worse in pt’s with pulmonary disease), miosis, n/v, increased intracranial pressure, orthostatic hypotension, constipation, biliary colic (constriction of sphincter of oddi leading to increased pressure in bile duct/gallbladder), urinary retention, prolonged labor, itching and hives.

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24
Q

Why are opioids absolutely Contraindicated in patients that already have increased intracranial pressure due to trauma or other causes?

A

Opioids will increase intracranial pressure as its effect: decreased respiration means increased CO2 –> cerebral vasodilation –> increased cerebral blood flow –> Increased cranial pressure.

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25
Why can't we give opioids in women that are in labor?
All but one opioid will prolong labor.
26
What effects do opioids have on the urinary system?
Inhibition of the urinary voiding reflex, increased external sphincter tone and increased bladder volume all leads to urinary retention and urinary colic exacerbation.
27
When will opioid dosage adjustment be necessary?
In patients with renal or hepatic insufficiency.
28
What are 3 instances where opioids are absolutely contraindicated?
In cases of head injuries (increased intracranial pressure), patients with pulmonary issues and patients with asthma (because opioid induced mast cell activation may lead to bronchoconstriction which will exacerbate asthma).
29
Opioid use and preggo?
Opioids crosses the placenta so when the baby is born it will show withdrawal symptoms.
30
What are some DDI's with opioids? What's special about opioids, particularly Meperidine, and MAOIs?
Anything that messes with the CNS such as sedatives-hypnotics, antipsychotics and TCAs, MAOI's (because they have been shown to have high incidence of hyperpyrexic coma and HTN, relative CI for all opioids, ABSOLUTE CI for Meperedine --> Serotonin syndrome).
31
Morphine gets glucoronidated into two active metabolites, what are they and what are their effects?
They are M3G and M6G. M3G has no analgesic effects but is neuroexcitatory (GABA/glycine system), so if enough accumulates it can induce seizures particularly in the elderly. M6G has 4-6x the potency of morphine in terms of analagesic activity.
32
General PK of morphine in terms of bioavailibility and half life?
High first pass metabolism thus low bioavailibility and short half life (less than 2 hrs).
33
What is the chemistry of Codeine aka methylmorphine?
It is a prodrug of morphine, however only 10% is converted, the rest gets smashed through the high first pass metabolism.
34
How is codeine metabolized?
Codeine --> CYP 2D6 --> Morphine, and then morphine gets glucuronidated into M3G and M6G.
35
Whats special about the CYP that metabolizes Codeine?
2D6 metabolizes codeine, however there are polymorphisms in 2D6 so some people have fast metabolism (in which case more morphine is made which will then cause toxic effects in standard dose) and some have low metabolism (in which case no tx level is reached with standard dose).
36
In terms of activity which is stronger, codeine or morphine?
Codeine has 60% of the affinity of the Morphine-like Opioid Receptors (MOR), so morphine is stronger, codeine is a PARTIAL AGONIST.
37
When would we use codeine vs morphine?
Morphine is the heavy artillery used only for extreme pain, whereas codeine is for mild to moderate pain in conjunction with an NSAID or other analgesic.
38
Tx uses of Codeine?
Mild to moderate analgesic used with NSAIDs, and also cough suppression.
39
What is the active metabolite of Meperidine and what is special about this metabolite?
Active metabolite is "Normeperidine" and this thing has 1/2 the analgesic effects of meperidine, however 2-3x more neuroexcitatory effects. Further, it has a 15-20 hr halflife which is even higher in renally or hepatically impaired, (to only 3 hrs of meperidine), so it can accumulate very easily. Anxiety, tremors and seizures will occur if enough accumulates.
40
What are some Pharmacodynamics of meperidine in terms of receptors it hits?
It is a strong mu opioid agonist, an ok k receptor agonist. Has antimuscurinic effects (i.e. anti parasympathetic effects, BUT it might not cause miosis as expected of anti-cholinergic drugs).
41
When is meperidine used?
For moderate to severe pain, however limit is 48 hours and cannot use in high doses due to the active metabolite normeperidine. Can also be used in LABOR (the only opioid that can do this, the rest is contraindicated in labor). Adjunct to anasthesia. Also can be used for shivering due to anasthesia or due to the infusion rxn of amphotericin B and trastuzamab (possibly through the alpha 2 adrenoreceptor).
42
Can Meperidine be used in labor?
Yes, it does not delay the birth process and does not antagonize the effects of oxytocin, and also the fetus may experience less respiratory depression
43
What can be used for a patient who is shivering due to the effects of anasthesia or infusion rxns from trastuzamab or amp B?
Meperedine, because of possible effects it might have via the alpha 2 receptors.
44
In addition to class effects, what are unique AE's of meperidine?
Tachycardia (anti-cholinergic effects), hypotension (which will induce reflexive tachycardia + the anticholinergic tachycardia = extreme tachycardia ). Neurotoxicity due to normeperidine accumulation.
45
What are some DDI's of Meperidine?
Cannot use with MAOIs, (will cause serotonin syndrome). Phenobarbitol and phenytoin (CYP inducers) will increase systematic clearance and decrease the bioavailibility of meperidine and increase plasma conc of meperidine.
46
What are some notable chemistry of Fentanyl?
Highly lipid soluble and high affinity for the mu receptor and as a result this drug works extremely quickly, but also has quick termination. Comes IV, transdermal and bucchal.
47
Metabolism of Fentanyl?
Hepatic and extrahepatic.
48
What should be considered before administering the transdermal patch of Fentanyl?
CANNOT be administered to an opioid naive patient because they are going to be more susceptible to the drug and hit the toxic levels quickly.
49
What are some adverse effects of Fentanyl? (In addition to class effects)
Truncal rigidity, hypo or hypertension.
50
What is special about the drug Methadone and its use?
It has a very high half life (15-40 hours) but in addition because of the long half life it can be used to treat patients that are heroin users so that they can quit.
51
Metabolism of Methadone? Excretion?
CYP 3A4, 2C9 and 2B6, biliary and renal excretion (increased excretion if urine is higher than 6 pH).
52
How does Methadone play with NDMA receptors and MOA agonists?
Since it is a long acting MOR agonist, it might block the NDMA R's and Monoamine transporters.
53
Uses of Methadone?
Heroine and opioid abusers, chronic pain.
54
What is special about the drug Tramadol in terms of its activity?
Its a weak MOR agonist, and also a serotonin and NorEpi reuptake inhibitor.
55
How is Tramadol metabolized and is anything special about its metabolite?
Metabolized by 3A4 and 2D6 to the metabolite M1, which has 2-4x the potency of the original drug.
56
Uses of Tramadol?
Mild/moderate pain, used with other NSAIDs and such.
57
AE's of Tramadol?
N/V, dizziness, dry mouth, sedation, headache and constipation. Decreases seizure threshold and can cause seizures even at recommended doses.
58
DDI's with Tramadol?
SSRI's, other opioids, TCA's, antipsychotics, MAOIs, 2D6 and 3A4 inhibitors.
59
Contraindications of tramadol?
Patients with pulmonary function impairment.
60
Tolarence and withdrawal tendency of tramadol?
Very high. High abuse potentials.
61
What is the concept behind Anti-diarrheals?
They are opioid agonists that inhibit excessive GI motility and propulsion, however they do not cross the BBB at low doses.
62
Whats special about Diphenoxylate (with atropine)?
Metabolized to difenoxylic acid (active), no morphine like CNS effects at low doses, but at high doses euphoria and physical dependence is achieved with chronic use.
63
What is associated with Loperamide? Why is Pgp interactions important with Loperamide (aka immodium)?
It is a Pgp substrate, it has poor absorption, poor CNS penetration due to poor penetration through BBB, hepatic metabolism with no active metabolite. Pgp inhibitors will increase CNS loperamide conc.
64
When should anti-diarrheals not be used?
Avoid use in bowel ostructions and hemmorhagic diarrhea. Don't use in babies less than 2 years old.
65
What is the concept of "Ceiling effect" of opioids?
No further effect of analgesia and respiratory depression above a certain dose.
66
What receptors does Butorphanol hit?
KOR agonists, MOR antagonists.
67
Uses of Butorphanol?
Migrane pain (nasal formulation) and acute pain.
68
What happens at high doses of Butorphanol?
Psychomimetic effects, more sedation, hypotension and tachycardia (reflexive).
69
Receptor affinity of Buprenorphine?
Partial MOR agonist but still high affinity for MOR. KOR and DOR ANTAGONIST.
70
What can respiratory depression be treated with and why would this not work post administration of Buprenorphine?
Naloxone can tx respiratory depression, however if respiratory depression is Buprenorphine induced it wont work (slow dissociation from opoid receptor). If administered naloxone before Buprenorphine however, it will work.
71
Metabolism of Buprenorphine?
CYP3A4 to Norbuprenorphine which is an active metabolite.
72
PK of Buprenorphine?
IV, IM, transdermal, sublingual. VERY HIGH HALF LIFE (35 hours).
73
Uses of Buprenorphine?
Moderate to severe acute and chronic pain, tx of opioid dependence, and the effects are typical of what you find in morphine.
74
What is special about opioid antagonists?
Usually it is useless unless there is an opioid agonist around.
75
How do opioid antagonists work?
Basically they bind to the opioid receptor but doesn't activate the receptor, blocking the agonists from binding to the receptor.
76
Which receptors do opioid antagonists hit?
Hits the MORs preferentially, lower affinity for the KOR and DOR, but can reverse agonists at K and delta sites.
77
What is special about the drug "Naloxone?" How is it administered? How long does it take to kick in via IV? How long does it last?
It is the tx of choice for opioid overdose, and has a very short half life. IV, IM, subQ and endotracheal. 2 mins to have effect kick in, lasts 30 to 120 mins.
78
What is a potential problem with Naloxone and patients who ore opioid dependent?
Instant withdrawal symptoms upon administeration of Naloxone.
79
Which drugs might require a higher dose of Naloxone?
Buprenorphine and Pentazocine.
80
What are the clinical uses of naltrexone?
Alcoholism abusers, it decreases ethanol cravings and prevents alcohol relapse. Used to tx opioid relapse in compliant patients.
81
Contraindications and AE's of Naltrexone?
Hepatotox which is dose related, (narrow window), CI-ed in liver failure, acute hepatitis, acute opioid withdrawal, and a positive urine screen.
82
Which are the 2 peripherally acting opioid antagonists? What is the point of this class?
Methylnaltrexone and Alvimopan. Selective competetive inhibitors of MOR in the GI tract, does not trigger opioid analgesic effects or induce opioid withdrawal. Basically antagonizes the unwanted effects of opioids in the GI.
83
What is the clinical use of Methylnaltrexone?
Tx opioid induced constipation when laxative therapy doesnt work.
84
Clinical use of Alvimopam? Potential problem?
Short term hospital use in tx of ileus however there is an increased incidence of MI's with this drug.
85
Which is the only opioid that has activity in all opioid receptors (mu delta and kappa?)
Sufentanil.
86
Which is the only opioid that is an agonist for mu and an antagonist for kappa and delta?
Bruprenorphine

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