Pain 2 Flashcards
What is the recommendation for a pt with substance use disorder suffering from non-cancer chronic pain?
avoid opioids (use simple analgesics and non-pharm stuff only)
What is the recommendation for a pt with a psychiatric disorder suffering from non-cancer chronic pain?
Avoid opioids until disorder is stabilized
What’re the upper limits of opioid dosing for chronic non-cancer pain?
When starting, no higher than 50mg morphine equivalents/day
If we must go up, no higher than 90mg morphine equivalents per day
What should we do if we increase the dose of an opioid a couple of times without any chronic pain reduction?
a. further increase the dose
b. change the opioid
c. switch to NSAIDs
b.
Opioid MOA
Agonist for opioid receptors in CNS and PNS > suppress neuronal firing > alters pain perception
T or F: Opioids reduce pain and inflammation.
F
They do nothing for inflammation
Which opioid receptor is most responsible for the analgesic effects of opioids?
µ (mu)
Name the 3 opioid receptors
mu, delta, kappa
T or F: Opioids are a subset of opiates.
F
Opiates are a subset of opioids
Advantages of opioids?
strong pain relief, no major organ tox
Disadvantages of opioids?
AEs (constipation, CNS depression, falls/fractures, apnea, hyperalgesia)
Addiction (OUD)
tolerance, dependence
No long-term trials (> 3 months)
The “big 5” opioids in Canada
morphine, codeine, hydromorphone, oxycodone, fentanyl
How does codeine provide pain relief?
It must be converted to morphine first via CYP2D6
What kind of opioid formulation should inds always be started on?
immediate release
T or F: If an ind is expected to be on opioids chronically, then using dosage forms other than IR (e.g. SR, CR, ER) are acceptable first-options.
F
IR is always first option regardless
How potent are parenteral opioids (IM, IV, SC) compared to po opioids?
Parenteral opioids are ~2x more potent than po opioids
How do we convert b/w potencies of diff types of opioids?
By using an oral morphine equivalent factor (ORAL and MORPHINE are the standard)
Why don’t some ppl experience analgesia from codeine?
Bc they’re deficient in the 2D6 enzyme > no morphine is produced from codeine precursor
Which oxycodone product was d/c’ed? Why?
OxyContin > it was being abused (it was v. addictive)
Active metabolite of morphine?
morphine-3-glucuronide
When would you consider avoiding morphine?
renal dysfn due to accumulation of metabolites
opioid of choice in CKD/renal impairment pts?
Dilaudid (hydromorphone)
MOA of tramadol?
mu receptor agonist AND SNRI
What pt pop would you avoid tramadol in? Why?
Seizure pts > lowers seizure threshold
How much stronger is fentanyl than morphine?
~100x
Dosing schedule of fentanyl patch?
q72h
T or F: Fentanyl will accumulate in renal impairment
F (no active metabolites)
What do you do if the fentanyl patch’s gel gets on your hand while applying the patch?
Wash your hand w/ water ONLY (soap w/ increase absorption)
Which strength of fentanyl patch is used for dosing titrations/tapers?
the 12mcg/hr patch
Starting dose of fentanyl patch for pain?
25mcg/hr
Dosing interval for methadone for pain tx
q8-12h (for pain relief)
T or F: Methadone will accumulate in renal impairment
F
Name 3 opioids that’re appropriate during renal impairment
Dilaudid (hydromorphone), fentanyl patch, methadone
What kind of test should be performed prior to starting methadone?
baseline ECG
Methadone doses can be increased no less than every ___ days
5
Why is an ECG recommended when using methadone?
Bc there’s a risk of QT prolongation
Why does respiratory depression insidiously develop in methadone pts?
bc methadone has a slow onset of action
What is the initiating dose of methadone?
≤ 30mg (depending on risk of methadone tox)
General short term AEs of opioids:
sedation, resp. dep, constipation, N, itching/rash
Which opioid AEs will pts never develop tolerance for?
constipation and miosis (pin-point pupils)
What’s important to know about resp dep and opioid tolerance?
Tolerance to resp dep is lost quickly > if a pt goes w/o opioids for ≥ 3 days, their tolerance has decreased and can die if they take the same dose they’ve been taking previously
When does opioid tolerance to sedation begin?
3-4 days after initiating tx
Opioid CIs?
- allergy
- co-admin of a drug that interacts w/ it which could have important consequences for pt’s health (e.g. rifampin)
- active diversion of ctrled substances
General long term AEs of opioids:
- hypogonadism
- sleep apnea
- opioid-induced hyperalgesia
- opioid use disorder
How do opioids affect the hypothalamic-pituitary-gonadal axis?
Over the long term, opioids cause a DECREASE in LH, FSH, testosterone, and estrogen
It also causes an INCREASE in prolactin
How do opioids affect the hypothalamic-pituitary-adrenal axis?
they decrease plasma cortisol levels over time
What sx’s of hypogonadism are expected from chronic opioid use?
reduced libido, aggression, amenorrhea, irregular menses; and galactorrhea
T or F: The sx’s of sleep apnea caused by opioids is similar to obstructive sleep apnea sx’s.
T
When would hyperalgesia be more likely to develop?
With higher doses of opioids, and when opioids are used for longer periods of time
T or F: Decreasing doses of opioids helps w/ hyperalgesia.
T
T or F: Many inds on opioid tx for chronic pain will develop opioid use disorder.
T
What is first line for tx of opioid use disorder?
Suboxone (buprenorphine/naloxone)
MOA of naltrexone?
full antagonist of opioid receptor
MOA of methadone?
full agonist of opioid receptor
MOA of Suboxone?
partial agonist of opioid receptor
Most likely to get an overdose w/:
- full opioid agonist
- partial opioid agonist
- opioid antagonist
full opioid agonist
What’s an advantage of bupenorphine being a partial agonist?
Safer in overdose due to ceiling effect
What’s the advantage of having naloxone in Suboxone?
It blocks the effects of buprenorphine if injected (i.e. it makes injection futile)
T or F: Naloxone is absorbed along with buprenorphine, making it slightly less effective.
F
naloxone is NOT absorbed po or SL
Advantages of Suboxone over methadone?
- less risk of overdose
- less AEs
- reduced risk of diversion
- less DIs
- milder withdrawal sx’s when discontinued
What is the first thing we need to do when switching from one opioid to another?
Calculate TOTAL DAILY OPIOID USE (inc. avg. PRN use)
After we have the total daily opioid use, what do we do next?
Convert it to total daily oral morphine equivalent
When converting to total daily oral morphine equivalent, what should we keep in mind?
potency diffs b/w po and parenteral opioids (i.e. if we are starting with an injectable, then multiply the total daily oral morphine equivalent by 2)
After calculating our total daily oral morphine equivalent, what do we do?
Reduce dose (to account for incomplete cross tolerance)... a. if total daily oral morphine equivalent is ≥ 200mg, reduce by 50%
a. if total daily oral morphine equivalent is < 200mg, then reduce by 25%
Ok, now we have our final total daily oral morphine equivalent after reducing to account for incomplete cross tolerance. What do we do now?
Convert it to new opioid daily dose (interval is the same as previous opioid’s interval)
How do we calculate the new PRN dose?
New opioid daily dose * 10% (i.e. new prn dose is 10% of new opioid daily dose)
PRN dosing interval is also the same (if none, then q4-6h)
If converting total daily morphine dose to total daily oral morphine equivalent, what do we multiply it by?
1
If converting total daily codeine dose to total daily oral morphine equivalent, what do we multiply it by?
0.15
If converting total daily oxycodone dose to total daily oral morphine equivalent, what do we multiply it by?
1.5
If converting total daily hydromorphone dose to total daily oral morphine equivalent, what do we multiply it by?
5
When may we switch a pt to a fentanyl patch ?
When the pt has been on 60mg/d of total oral morphine equivalence for two consecutive weeks
