17 - Neuropathic Pain Flashcards
For a 70 year old with painful diabetic neuropathy (PDN), what drugs do you want to avoid?
- drugs that cause orthostatic hypotension or dizziness/unsteady on her feet
- maybe things that cause sedation
Describe the DN4 questionnaire
- If score greater than or equal to 4, test is positive
- 83% sensitivity
- 90% specificity
What are the 3 areas to target neuropathic pain?
- spontaneous ectopic activity (peripheral)
- central sensitization
- disinhibition
How do Gabapentinoids work?
- mostly on the calcium channel
- work on central centization
How do TCA’s work?
- NE/5-HT receptor
- work on disinhibition
- also working on yellow guys on the spontaneous ectopic activity (sodium channels)
How do SNRI’s work?
- NE/5-HT receptor
- prob disinhibition ?
How does Tramadol work?
- bit of an SNRI or TCA and works on disinhibition
- also works on opioid receptor so central sensitization
How does Lidocaine work?
-fits on peripheral part, working with sodium channels
Describe the weight of evidence for pain meds by neuropathic pain type (greatest to least evidence)
- Painful Diabetic Neuropathy
- Post-herpetic neuralgia
- Mixed neuropathies
- Peripheral Nerve Injury (ex. post-amputation)
- Central Pain (ex. post-stroke, MS, SCI)
- HIV Neuropathy
Is tramadol an exception to opioids for PDN ?
Is it unique?
-MOA weak m-opioid receptor agonist activity & inhibition of NE/5-HT reuptake
Although tramadol has a lower potential for abuse compared with other opioids, given these safety concerns, it is not recommended for use at first or second-line agent
Pain decrease does not equal increased QOL or functioning.
Of 26 studies in neuropathic pain, showing a meaningful decrease in pain, only 11 reported a significant improvement in QOL
Notable side effects of TCA’s
- anticholinergic (dry mouth, constipation, sedation)
- weight gain
- orthostatic hypotension
Cautions with TCA’s
- elderly
- dementia
- glaucoma
- urinary retention
- cardiac disease
Notable side effects with Gabapentin, pregabalin
- dizziness
- imbalanced
- sedation
- peripheral edema
Cautions with gabapentin, pregabalin
- elderly
- existing edema
- fall risk
- abuse potential
Notable side effects of SNRI’s
- nausea
- increase BP
- dizziness
Cautions with SNRI’s
- HTN?
- bipolar disorder (NE can flip bi-polar patients into hypomania)
Notable side effects of Tramadol
- nausea
- constipation
- sedation
- dizziness
Cautions with tramadol ?
- opioid dependence/addiction risk
- seizure risk
What type(s) of pain do we have good non-pharms for? What about bad non-pharms?
- With back pain we have lots of non-pharms that are maybe more effective than meds
- With neuropathic pain, we don’t have that many
Does exercise improve neuropathic pain?
- exercise does not help
- no evidence that it improves neuropathic pain
- may be a distraction technique
Does exercise help fibromyalgia?
yes
What are non-pharms for neuropathic pain?
- Behavioral, psychosocial, physical & other therapies (ex. music) are essential for successful long-term management
- Interdisciplinary intervention may decrease drug requirements
- Pain reduction and improved function, not pain elimination, is the goal of drug therapy. Those with CNCP must be helped to refocus on positive, incremental gains. Dedicated therapists and/or CNCP programs are helpful
look at slide 19
ok
Describe the fast track approach to neuropathic pain meds
increase dose by 50-100% q3d
Describe the cautious driver approach
increase dose by 50-100% q1w
What are some practicalities of dosing neuropathic pain meds?
Always start low & go slow - this is a chronic condition:
- There is no rush
- Not worth risking harm to the patient
- Side effects may result in a loss of a viable option in the mind of the patient
*Higher doses have a low likelihood of resulting in greater benefit and are more likely to result in greater harm
What PDN drug will help with depression/anxiety ?
- TCA
- SNRI
What PDN drug will help with insomnia ?
- Gabapentin, pregabalin ?
- TCA
What PDN drug will help with osteoarthritis ?
- duloxetine
- tramadol ?
*not great studies
What PDN drug will help with most other types of neuropathic pain?
- SNRI
- TCA
- gabapentin
- pregabalin
- tramadol ?
Which PDN drug is not covered by Pharmacare?
Tramadol
What are we monitoring for?
Efficacy:
- Pain level
- Functioning
- Mobility
- Exercise tolerance
- Sleep
- Socialization
- Psychological status
Side Effects
Monitor for SE in a week, efficacy will not show up in a week
When are we monitoring?
Depends on:
- Rate of titration desired
- Self-management abilities of patient
see slide 25
ok
Describe the results of the trial with gabapentin + opioid vs gabapentin
NNT = NNH
- you’re essentially harming the same number of people you’re treating
- with concerns of long-term opioid use
Topical Neuropathic Pain Med:
Describe Lidocaine
- 5% plaster or patch most studied - modest benefit in low quality, short-term trials
- ointment compounded at some local pharmacies - equally effective ??
- applied TID - QID
-1st or 2nd line in several guidelines for PHN
Advantage:
- Onset immediate
- Minimal systemic absorption
Topical Neuropathic Pain Med:
Describe Capsaicin
- 0.075% gel - insufficient data to draw conclusions
- 8% patch (NNT = 11) not available in Canada
- just adds more burning, doesn’t really work
Topical Neuropathic Pain Med:
Describe Ketamine Alone
Case series supporting pain relief vs. placebo
Topical Neuropathic Pain Med:
Describe Amitriptyline + Ketamine
questionable
What are some patient counselling points?
- NNT, % response
- When is a reliable benefit likely to be seen?
- Side effects (likelihood of them happening)
- Approximate costs
Avoid creating what type of patients?
1) Always wanting more - minimize drug-centricity
2) Stuck, but not knowing how to get free - minimize pharmacological messiness
