17 - Neuropathic Pain

Question 1

For a 70 year old with painful diabetic neuropathy (PDN), what drugs do you want to avoid?

Answer 1

• drugs that cause orthostatic hypotension or dizziness/unsteady on her feet
• maybe things that cause sedation

Question 2

Describe the DN4 questionnaire

Answer 2

• If score greater than or equal to 4, test is positive
• 83% sensitivity
• 90% specificity

Question 3

What are the 3 areas to target neuropathic pain?

Answer 3

• spontaneous ectopic activity (peripheral)
• central sensitization
• disinhibition

Question 4

How do Gabapentinoids work?

Answer 4

• mostly on the calcium channel

- work on central centization

Question 5

How do TCA’s work?

Answer 5

• NE/5-HT receptor
• work on disinhibition
• also working on yellow guys on the spontaneous ectopic activity (sodium channels)

Question 6

How do SNRI’s work?

Answer 6

• NE/5-HT receptor

- prob disinhibition ?

Question 7

How does Tramadol work?

Answer 7

• bit of an SNRI or TCA and works on disinhibition

- also works on opioid receptor so central sensitization

Question 8

How does Lidocaine work?

Answer 8

-fits on peripheral part, working with sodium channels

Question 9

Describe the weight of evidence for pain meds by neuropathic pain type (greatest to least evidence)

Answer 9

• Painful Diabetic Neuropathy
• Post-herpetic neuralgia
• Mixed neuropathies
• Peripheral Nerve Injury (ex. post-amputation)
• Central Pain (ex. post-stroke, MS, SCI)
• HIV Neuropathy

Question 10

Is tramadol an exception to opioids for PDN ?

Answer 10

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

Question 11

Pain decrease does not equal increased QOL or functioning.

Answer 11

Of 26 studies in neuropathic pain, showing a meaningful decrease in pain, only 11 reported a significant improvement in QOL

Question 12

Notable side effects of TCA’s

Answer 12

• anticholinergic (dry mouth, constipation, sedation)
• weight gain
• orthostatic hypotension

Question 13

Cautions with TCA’s

Answer 13

• elderly
• dementia
• glaucoma
• urinary retention
• cardiac disease

Question 14

Notable side effects with Gabapentin, pregabalin

Answer 14

• dizziness
• imbalanced
• sedation
• peripheral edema

Question 15

Cautions with gabapentin, pregabalin

Answer 15

• elderly
• existing edema
• fall risk
• abuse potential

Question 16

Notable side effects of SNRI’s

Answer 16

• nausea
• increase BP
• dizziness

Question 17

Cautions with SNRI’s

Answer 17

• HTN?

- bipolar disorder (NE can flip bi-polar patients into hypomania)

Question 18

Notable side effects of Tramadol

Answer 18

• nausea
• constipation
• sedation
• dizziness

Question 19

Cautions with tramadol ?

Answer 19

• opioid dependence/addiction risk

- seizure risk

Question 20

What type(s) of pain do we have good non-pharms for? What about bad non-pharms?

Answer 20

• 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

Question 21

Does exercise improve neuropathic pain?

Answer 21

• exercise does not help
• no evidence that it improves neuropathic pain
• may be a distraction technique

Question 22

Does exercise help fibromyalgia?

Answer 22

yes

Question 23

What are non-pharms for neuropathic pain?

Answer 23

• 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

Question 24

look at slide 19

Answer 24

ok

Question 25

Describe the fast track approach to neuropathic pain meds

Answer 25

increase dose by 50-100% q3d

Question 26

Describe the cautious driver approach

Answer 26

increase dose by 50-100% q1w

Question 27

What are some practicalities of dosing neuropathic pain meds?

Answer 27

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

Question 28

What PDN drug will help with depression/anxiety ?

Answer 28

- TCA | - SNRI

Question 29

What PDN drug will help with insomnia ?

Answer 29

- Gabapentin, pregabalin ? | - TCA

Question 30

What PDN drug will help with osteoarthritis ?

Answer 30

- duloxetine - tramadol ? *not great studies

Question 31

What PDN drug will help with most other types of neuropathic pain?

Answer 31

- SNRI - TCA - gabapentin - pregabalin - tramadol ?

Question 32

Which PDN drug is not covered by Pharmacare?

Answer 32

Tramadol

Question 33

What are we monitoring for?

Answer 33

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

Question 34

When are we monitoring?

Answer 34

Depends on: - Rate of titration desired - Self-management abilities of patient

Question 35

see slide 25

Answer 35

ok

Question 36

Describe the results of the trial with gabapentin + opioid vs gabapentin

Answer 36

NNT = NNH - you're essentially harming the same number of people you're treating - with concerns of long-term opioid use

Question 37

Topical Neuropathic Pain Med: | Describe Lidocaine

Answer 37

- 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

Question 38

Topical Neuropathic Pain Med: | Describe Capsaicin

Answer 38

- 0.075% gel - insufficient data to draw conclusions - 8% patch (NNT = 11) not available in Canada * just adds more burning, doesn't really work

Question 39

Topical Neuropathic Pain Med: | Describe Ketamine Alone

Answer 39

Case series supporting pain relief vs. placebo

Question 40

Topical Neuropathic Pain Med: | Describe Amitriptyline + Ketamine

Answer 40

questionable

Question 41

What are some patient counselling points?

Answer 41

- NNT, % response - When is a reliable benefit likely to be seen? - Side effects (likelihood of them happening) - Approximate costs

Question 42

Avoid creating what type of patients?

Answer 42

1) Always wanting more - minimize drug-centricity | 2) Stuck, but not knowing how to get free - minimize pharmacological messiness