Opioid therapeutics Flashcards
(77 cards)
What are the 3 families of endogenous opioid peptides + receptors? Which as the highest affinity for mu opioids receptors?
- Beta-endorphins (highest affinity)
- Mu receptor - Met/Leu Enkephalins
- delta - Dynorphins
- kappa
What occurs pre-synpatically in the ascending pathway when opioids are used
Mechanism 1: INHIBITS Ca2+ channels
= Less calcium comes into pre-synaptic terminal
= reduced excitatory release of neurotransmitters (glutamate, substance P, PGs) from vesicles fused at the terminal end of neuron
= less neurotransmitters flow across synapse to second order neurons
= REDUCED PAIN SIGNALLING TO THE NEXT SECOND ORDER NEURONS
Mechanism 2: ACTIVATES K+ channels
= K+ ions exist pre-synaptic terminal
= hyperpolarization of cell
= NO ACTION POTENTIAL is generated
= REDUCED PAIN SIGNALLING TO THE NEXT SECOND ORDER NEURONS
What occurs post-synaptically after using opioids
By mechanism 2: ACTIVATES K+ channels
= K+ ions exist post-synaptic terminal
= hyperpolarization of cell
= NO ACTION POTENTIAL is generated
= REDUCED PAIN SIGNALLING TO THE ASCENDING TRACTS TO THE BRAIN
What is the MOA of opioids on the descending pathway
- Opioids bind to mu receptors on GABA interneurons (pre-synaptically & post-synaptically).
- This reduces the activity of GABA.
- PAG communicates with rostral ventral medulla (RVM) and raphe nuclei to release serotonin, norepinephrine, and enkephalins.
- These neurotransmitters inhibit pain signals at the dorsal horn of the spinal cord, reducing pain perception.
What is the morphine equivalent dose that we avoid going over
80mg
Who do we not use opioids in?
- Opioids overdose hx
- Alcohol use disorder (current)
- Substance use disorder hx
- Mental health disorder ?
Which opioid is least affected by CYP p-450?
Which is most?
Least: hydromorphone
Most: Methadone
T/F Opioids are organ-toxic
False
What type of pain is better relieved by opioids
Continuous, dull pain
Rather than sharp intermittent, lancinating type of pain
What 2 dimensions of pain do opioids work on?
1 - somatosensory aspect (perception of pain location, type, intensity)
2 - modulates emotional aspect of pain
How do opioids affect mood? When does it occur/stop?
Euphoria, anxiety relief in the beginning
Chronic pain has no euphoria noted
Initial relief of depression but chronic opioid use can exacerbate depression
When does sedation in opioids stabilize
Stabilize in 1-2 weeks
- can get tolerance to it
Do not combine with sedatives, benzodiazepines, alcohol
What is the MOA of N/V in opioid use? Treatment
Stimulates chemoreceptor trigger zone (located in medulla)
= enhanced vestibular sensitivity
= delayed gastric emptying
If intolerable, consider opioid rotation
Can treat with ondansetron, prochlorperazine, or scopolamine
Define respiratory depression
A rise in peripheral PCO2 + fall in peripheral O2
plus reductions in rRR which leads to hypoxia and death
- dose-dependant
- always preceded by sedation for 5-15 min
What are high risk patients for opioids for respiratory depression? (5)
- Obese patients
- patients with abnormal airways - large neck
- Narrow airway passage in through (large tonsils)
- Family or personal history of sleep apnea
- Asthma, COPD, CHF
Which medications prescribed with opioids can cause suppression of breathing centers (4)
- Anesthesia
- Sedatives (benzo, zopiclone)
- Muscle relaxants
- Alcohol
- Mood altering drugs
- Gabapentin/pregabalin at high doses
When could RD occur?
- In opioid-naive patients
- dose changes
- Rotation of opioids
- Post-op patients
- Tapering patients
What is used for rapid reversal of respiratory depression? MOA
Naloxone
- stronger receptor affinity than opioids as it kicks them off (blocks all receptors)
- no pain relief
What are signs of opioid overdose
Pupil constriction miosis (pinprick pupils)
Blue/grey lips
Sedated, soft or no breath, difficult to wake up
Doesn’t react to a sternal rub
What is the MOA of using hydrocodone for antitussive
Opioids depress cough centers in medulla & depress cough reflex (mu and kappa receptors responsible for this effect)
What endocrine effects do opioids have?
What do men have to watch out for?
Inhibits release of CRH, ACTH = decreased cortisol levels
Inhibits release of GNRH
= decreases LH, FSH
= decreases testosterone, estradiol, progesterone
= AFFECTS MENSTRUAL CYCLE & LIBIDO
Increases prolactin and ADH release anterior pituitary
*Suppresses thyroid, growth hormone and BMD
What do men have to watch out for with endocrine effects
- Counsel on OPIAD: Opioid Induced Androgen Deficiency
- Decreased testosterone levels with BOTH chronic pain & opioid use
- May result in worsening pain, depression, low energy, ED, infertility
- Check T levels
- Treatment with testosterone supplements or PD-5 inhibitors
What is the treatment for hyperhidrosis (abnormal sweating)
Clonidine 0.1mg PO BID - 0.2mg TID (watch BP)
Oxybutynin (watch in elderly as it is highly anticholinergic)
*May need to taper or rotate opioid use
What do you do if you experience pruritus on an opioid
Not a true allergy
- concentration dependent
- caused by a release of histamine from mast cells
Treatment
- Antihistamines: diphenhydramine, hydroxyzine
- Antipruritic agents: Aveeno baths
- Opioid rotation (more potent opioid = less histamine release)