Opioids Flashcards
Effects of opioid peptides can be antagonized by __
naloxone
Opioid receptors are ____ and the primary action is __ NT release and neuronal excitability
Gi/o linked
decrease
Mu (morphine) receptors are ____ anaglesia where as kappa receptors are ___ analgesia
spinal/supraspinal
spinal
SE of Mu receptors
- Respiratory depression
- Euphoria
- Decreased GI motility
- Miosis
- PHYSICAL dependence
SE of kappa (dynorphin) receptors
- Dysphoria
- Miosis
- Sedation
opioids elicit analgesia effects by 2 ways:
- elevation of pain threshold by activation of brain stem descending inhibitory CNS pathways in Periaqueductal gray
- Change in subjective response to pain in limbic system via inducement of tranquility, euphoria
Opioids can elevate pain threshold by activation of brain stem descending inhibitory CNS pathways in Periaqueductal gray to:
- presynaptically decrease release of substance P and glutamate (via decrease in Ca2+ influx)
- Postsynaptially decrease response of pain transmission neuron
Compare and contrast Opioids vs non-opioid analgesia
- Op. are more efficacious but more dangerous (resp. depresion)
- Op. are dose dependent whereas NSAIDS have ceiling effect
- analgesia w/o loss of consciousness as seen with general anesthetics
- No antipyretic or anti-inflammatory effects
- Greater potential for tolerance and dependence
- dull, persistent tonic pain [C fibers] relieved better than sharp superficial pain [Adelta] - both
Uses of opioids
- Anaglesics
- Anti-diarrheal
- Cough suppressant (dextromethorphan)
- MI (morphine-fentanyl)
- dyspnea from pulmonary edema associated w/ cardiac dysfunction
Why is morphine good for MIs
- decrease preload
- decrease inotropy
- Decrease chronotropy
- reduce myocardial oxygen consumption
- Relieves anxiety via limbic system
SE of opioids in short term use
- Constipation
- N/V
- Sedation
- Dizziness
- Itching
- Dry mouth
__ and __ is NOT seen with therapeutic doses of nonopioid analgesics
Sedation and CNS depression
Which category of OTC products contains agents that are most likely to result in additive CNS depression if given to a patient who has been prescribed opioid analgesics for pain?
A. Analgesics (e.g., ibuprofen)
B. Antihistamines (e.g., diphenhydramine)
C. Laxatives (e.g., psyllium seed)
D. H2 Blockers (e.g., ranitidine)
E. Antidiarrheal agents (e.g., loperamide)
B. Antihistamines (e.g., diphenhydramine)
1st generation**
Constipation w/ opioids is due to:
- direct– inhibit ENS fxn at myenteric plexus
2. indirect– decrease ACh release (anticholinergic)
How do you manage constipation caused by opioids
- prophylaxis laxative (stimulant (senna) + stool softner (docusate))
- PAMORAs (peripherally acting u-opioid receptor antagonist)- Naloxegol for failed lax. on opioids for chronic pain
*no studies have shown superiority of one laxative over another
Describe the different OTC laxatives
- Stimulants (bisacodyl-senna)- often 1st line
- Osmotic (Miralax- sorbitol- PEG)
- Bulk-forming (psyllium)
- Stool softeners/wetting agents (docusate)- ineffective as monotherapy
Jackson is a 64-year-old male who has been treated for severe pain following a car accident in which he sustained a broken leg and broken arm. He has been converted to oral morphine in anticipation of his discharge. What other medication should he receive with his morphine upon discharge? A. Diphenhydramine B. Methylphenidate C. Docusate sodium with senna D. Docusate sodium E. Polyethylene glycol F. Prednisone
C. Docusate sodium with senna (stimulant + stool softener)
E. Polyethylene glycol (osmotic)
Adverse Reactions of Opioids
- Constipation
- Respiratory depression
- Sedation
- N/V
- Histamine release (itching)
- Flushing
- Urinary retention
- tolerance-dependence
Respiratory depression w/ opioids is the most serious acute SE but rarely a problem if therapy follows dosing guidelines. The primary action is ____ that leads to fall in RR
decrease in sensitivity of respiratory centers to CO2
**prominent sedation generally PRECEDES significant depression
What is the classic triad of sx with opioid overdose?
- Coma
- pinpoint pupils
- respiratory depression
How do you tx resp. depression w/ opioids?
- Naloxone- reserved for symptomatic resp. depression or progressive obtundation (NOT if somnolent but easily arousable)
* (DOA is shorter than agonists)
Respiration is depressed by an analgesic dose of: A. Morphine B. Naltrexone C. Buprenorphine D. Naproxen E. Hydrocodone F. Methadone G. Meperidine H. Tramadol
A. Morphine C. Buprenorphine (partial agonist) E. Hydrocodone F. Methadone G. Meperidine H. Tramadol (mixed action opioid)
Cause of N/V w/ opioids
Direct stimulaiton of the CTZ in medulla
*MC in ambulatory pts so may have vestibular component
Tx of N/V w/ opioids
- Antagonist of receptors in the periphery and at the CTZ
1. Antihistamine: if N related to ambulation (Diphenhydramine-meclizine)
2. D2 antagonists (1st line- inexpensive): Prochlorperazine, haloperidol
3. 5HT3 antagonists: Ondansteron more expensive)
4. Decrease movement
5. take w/ food and water
Sx of pseudo-allergy w/ opioids
- Itching
- Urticaria
- Flushing/local vasodilation
- Mild hypotension
- Can exacerbate asthma (H-induced bronchospasm)
*due to opioid induced release of HISTAMINE from mast cells NOT IgE mediated anaphylaxis
Tx of pseudo-allergy w/ opioids
- Antihistamines
Tx of true allergy w/ opioids
- Can try switching to different structural class (semisynthetic to synthetic)–> evidence lacking that switching reduces cross-sensitivity
- pretx w/ antihistamine and GC
Tx of opioid OD
- airway
- Ventilate
- Naloxone (see increase in RR in 1-2 min., may precipitate W/D in addicts that are dependent)
Describe the difference btwn Tolerance, Dependence and Withdrawal
Tolerance: need an increase dose to achieve the same effect (>2-3 weeks)
Dependence: chronic dosing alters physiological state so continued administration is required to prevent WD syndrome
Withdrawal: stop abruptly get WD sx
Tolerance less complete to ___ and __ so increasing analgesic dose –> worsens of these SE
-Tolerance is lost in ___ following discontinuation
constipation (and miosis)
1-2 weeks
**No matter how much tolerance develops - a lethal dose will always exist!!
A patient who develops tolerance to a fixed dose of morphine:
A. Will be equally tolerant to all effects of that dose of morphine
B. Probably will be tolerant to the analgesic effect of methadone
C. Probably will be tolerant to the analgesic effect of hydrocodone
D. Often can be relieved of pain if the dose of morphine is increased
E. Will remain tolerant to that dose of morphine for greater than 3 months
B. Probably will be tolerant to the analgesic effect of methadone
C. Probably will be tolerant to the analgesic effect of hydrocodone
D. Often can be relieved of pain if the dose of morphine is increased
How do you tx tolerance/dependence
Taper discontinuation
Sx of Opioid withdrawal
- reverse of opioid agonist action
1. Mydriasis
2. anorexia
3. insomnia
4. yawning
5. sneezing
6. diarrhea
7. lacrimation
8. increase HR
9. increase BP
10. sensitivity to CO2
severity of WD sx depends on
half life
shorter half-life = more severe sx
Tx of opioid WD
- tapering doses
- Methadone
- Clonidine (suppress SNS overactivity)
**rarely life-threatening (resolves 7-10 days), but general CNS depressants (ethanol, benzodiazepines, or barbiturates) may result in death