26 - Cancer Pain Flashcards
(37 cards)
1
Q
Define opioid addiction
A
- Primary, chronic disease of brain reward, motivation, memory, and related circuitry
- No published reports in cancer px w/ no previous substance abuse hx
2
Q
Define physical dependence
A
- Occurrence of abstinence syndrome when the opioid is suddenly stopped
- Fairly common, need gradual withdrawal
3
Q
Define tolerance
A
- Decrease in one or more effects of the opioid
- Decreased analgesic effect due to tumour progression
4
Q
Briefly describe nociceptive pain
A
- Direct stimulation of intact nociceptors
- Transmission along normal nerves
- Somatic – easy to describe and localize (ex: aching, stabbing, throbbing)
- Visceral – difficult to describe and localize (ex: squeezing, cramping, sharp or dull)
- Tissue injury apparent
5
Q
Describe neuropathic pain
A
- Disordered peripheral or central nerves
- Compression, infiltration, ischemia, metabolic injury
- Pain may exceed observable injury
- Less responsive than nociceptive pain
- Poorly responsive syndromes likely have a neuropathic component
- Ex: burning, tingling, sharp, electric shock
6
Q
Causes of cancer pain
A
- Cancer itself (75-80%)
- Tumour involvement of the bone (30-70%)
- Tumour involvement of nervous tissue, viscera, blood vessels
- Tx of cancer (15-19%)
- Chemotherapy – peripheral neuropathy, mucositis
- Radiotherapy – plexopathy, pelvic pain
- Post-surgical – neuropathies
- Unrelated to cancer (3-5%)
7
Q
Tx related neuropathy
A
- Chemotherapy-induced (cisplatin, oxaliplatin, paclitaxel, thalidomide)
- Surgical
- Phantom limb pain
- Post-mastectomy or post-thoracotomy syndrome
8
Q
Tx related immunosuppression
A
- Post-herpetic neuralgia
- Topical compounded cream (combination of topical anesthetic, mu receptor blocker, neuropathic pain med, NMDA blocker) if area is small
- Oral combination of opioid + neuropathic pain med
9
Q
Codeine – metabolism and CI
A
- 10% metabolized by CYP2D6 to morphine which is responsible for analgesia
- Due to genetics:
- 5-10% of people will have no analgesic effect
- 1-29% will have a more pronounced effect
- Contraindicated w/ paroxetine, fluoxetine, quinidine, haloperidol
- Contraindicated in renal and liver dysfunction
10
Q
Morphine – metabolism and CI/ caution
A
- Hepatic metabolism
- 60% to morphine-3-glucuronide
- 10% to morphine-6-glucuronide (greater analgesic properties and fewer AE)
- 4% to normorphine (non-active, non-toxic)
- Avoid in renal dysfunction and failure
- Use w/ caution in severe liver dysfunction (increase dosing interval from q6h to q8h)
11
Q
Hydromorphone – metabolism, caution
A
- Metabolized to hydromorphone 3-glucuronide
- Use w/ caution in severe liver dysfunction
- Increase dosing interval from q6h to q8h
- Dosage conversion from IV to PO is 1:1
12
Q
When is hydromorphone preferred over morphine?
A
- Renal failure
- Elderly (> 60 y/o) due to decreased renal function
- Hx of rashes
- Nausea and constipation are a problem
- Sedation is a problem
13
Q
When is fentanyl preferred over morphine and hydromorphone?
A
- Elderly (> 60 y/o) due to decreased renal function
- Renal failure and severe liver dysfunction
- Hx of rashes
- When nausea and constipation are a problem
- When sedation is a problem
14
Q
When should caution be taken w/ fentanyl?
A
Caution w/ CYP 3A4 inhibitors (clarithromycin, voriconazole, grapefruit) and inducers (dilantin, rifampin, steroids)
15
Q
Methadone – oral BA, metabolism, MOA, duration of analgesia
A
- Oral BA > 85%
- Metabolized in liver = no active metabolites
- Blocks NMDA receptors
- Duration of analgesia = 4+ h
16
Q
Starting doses for IV and PO morphine and hydromorphone for opioid naïve px – moderate pain and frail
A
- 2.5 mg PO morphine
- 1 mg IV/SC morphine
- 0.5 mg PO hydromorphone
- 0.2 mg IV/SC hydromorphone
17
Q
Starting doses for IV and PO morphine and hydromorphone for opioid naïve px – severe pain and frail
A
- 5 mg PO morphine
- 2 mg IV/SC morphine
- 1 mg PO hydromorphone
- 0.5 mg IV/SC hydromorphone
18
Q
Starting doses for IV and PO morphine and hydromorphone for opioid naïve px – moderate pain and robust
A
- 5 mg PO morphine
- 2 mg IV/SC morphine
- 1 mg PO hydromorphone
- 0.5 mg IV/SC hydromorphone
19
Q
Starting doses for IV and PO morphine and hydromorphone for opioid naïve px – severe pain and robust
A
- 10 mg PO morphine
- 5 mg IV/SC morphine
- 2 mg PO hydromorphone
- 1 mg IV/SC hydromorphone
20
Q
Who should NEVER get a fentanyl patch?
A
- Opioid naive px
- < 18 y/o
- For acute pain
21
Q
Describe bystander apathy
A
- Belief that others in a group who see the same risks will intervene
- *No pt should ever walk out the door of your pharmacy w/o a face to face instruction on how to use and dispose of fentanyl patches
22
Q
Titration of opioids for cancer pain
A
- Correct dose is a compromise between sufficient pain relief, good cognitive function, and acceptable SE profile
- Start low and titrate slowly, elderly metabolize opioids differently due to decreased renal function and hepatic clearance
23
Q
Guidelines for opioid dose escalation
A
- Always increase by a percentage of the present dose based upon px pain rating and current assessment
- Mild pain (1-3/10) -> 25% increase
- Moderate pain (4-6/10) -> 25-50% increase
- Severe pain (7-10/10) -> 50-100% increase
24
Q
PO and IV dose of morphine equal to 100 mg PO codeine
A
- PO = 10 mg
- IV = 5 mg
25
PO and IV dose of oxycodone equal to 100 mg PO codeine
- PO = 5 mg
| - IV = n/a
26
PO and IV dose of hydromorphone equal to 100 mg PO codeine
- PO = 2 mg
| - IV = 1 mg
27
PO and IV dose of methadone equal to 100 mg PO codeine
- PO = 1 mg
| - IV = n/a
28
PO and IV dose of fentanyl equal to 100 mg PO codeine
- PO = n/a
| - IV = 50 ug
29
PO and IV dose of sufentanil equal to 100 mg PO codeine
- PO = n/a
| - IV = 5 ug
30
Steps to calculate equianalgesic doses
1. Calculate total daily opioid intake (regular and breakthrough doses)
2. Convert to morphine equivalents
3. Convert from morphine equivalent to new opioid
4. Start new product at 50-75% of calculated dosage
5. Evaluate frequently for uncontrolled pain and re-titrate, if needed
31
What is a typical breakthrough dose?
10-15% of daily dose
32
Fentanyl patch conversion process
- Takes 12-16 h to achieve therapeutic fentanyl serum levels
- Therefore, must provide pt w/ opioid coverage during the conversion period
- Ex: should be given hydromorphone immediate release at time of patch application (whatever the breakthrough dose is calculated as), 4 h after patch application, and 8 h after patch application
- Upon system removal, 17 h or more are required for a 50% decrease in serum fentanyl concentrations
33
Opioid side effects
- Common = constipation, N, somnolence, mental clouding
| - Less common = urinary retention, pruritus, myoclonus, amenorrhea, sexual dysfunction, headache
34
Opioid induced neurotoxicity (sx and tx)
- Sx = N, twitching/ myoclonus/ seizures, sleeping a lot, change in mental status, delirium, hallucinations, hyperalgesia
- Tx = hydration, change opioid or reduce dose, treat sx (hallucinations, agitation)
- Metabolites cause opioid induced neurotoxicity
35
Neuropathic pain – pharm options
- Opioids
- Anticonvulsants (gabapentin, pregabalin, carbamazepine)
- Antidepressants (duloxetine, amitriptyline, nortriptyline, venlafaxine, methadone)
- Cannabinoids
36
Cannabinoid indications (on and off label)
- On-label -> N/V from chemotherapy, chronic pain (neuropathic pain in MS and cancer), anorexia associated w/ HIV/AIDS, drug-resistant epilepsy
- Off-label -> PTSD, anxiety, insomnia, epilepsy, chronic daily headache, inflammatory conditions, neuropathic/ mixed pain
37
IV dose of codeine equal to 100 mg PO codeine
50 mg
