Neuropathic pain

Question 1

CASE 1 - PK, a 58-year-old Native American male, came
to the UNM Pain Clinic today for his pain
assessment. He was referred by his primary care physician. He has a 20-year history of diabetes.
 How would you assess his pain? . . . what are the steps

Answer 1

Question 2

Case 1 (continued)
 How would you assess pain?
 Step 1: We need to know. . . .about pain . . . about etiology of pain

Answer 2

1.) About pain
 Quality and quantity of pain (description, pain scale, etc.)
 Location 
 Previous treatment response – what medications has patient tried, effective or not effective. Why? 
 What makes pain better/worse
.
2.) About etiology of pain
 Cause of pain

Question 3

Case 1 (continued)
 How would you assess pain?
 Step 1: We need to know. . . .about daily activity. . . diagnosis and treatment plan

Answer 3

1.) About daily activities
 Duration of concomitant disease(s), disease states, psychiatric issues, etc.
.
2.) About diagnosis and treatment plan
 Accurate diagnosis
 Selection of appropriate medications
 Guideline and patient-specific factors

Question 4

Case 1 (continued)
 How would you assess pain?
 Step 1: We need to know. . .. About medical history and comorbidities. . . About diagnosis and treatment plan

Answer 4

1.) About medical history and comorbidities
 Duration of concomitant disease(s), disease states, mental status, etc.
 Important information for selection of treatment agent
.
2.) About diagnosis and treatment plan
 Accurate diagnosis
 Imaging, physical exam (e.g., neuro, muscle-skeletal exam)
 Current treatment plan, including medications
 Guideline and patient-specific factors

Question 5

Case 1 (continued)
 How would you assess pain?
 Step 1a: Pain assessment. . . Assess quality and quantity (general)

Answer 5

Question 6

Step 1a: Pain assessment
- Assess quality and quantity
OPQRST . . . Provocation or Palliation

Answer 6

 Medication(s)/treatment(s) tried
 Effective or not effective?
 If not effective, ask reasons (e.g., adverse reactions)

Question 7

Step 1a: Pain assessment
- Assess quality and quantity
OPQRST . . . Quantity of pain

Answer 7

Question 8

Step 1a: Pain assessment . . .Pain scale?

Answer 8

Question 9

Step 1a: Pain assessment. . . Comorbidities

Answer 9

Question 10

Step 1a: Pain assessment

 Other considerations: nonverbal communication

Answer 10

Question 11

Step 1b: Establishment of treatment

Answer 11

Question 12

Types of pain (review) part 1

Acute pain vs. chronic pain

Answer 12

 Acute pain: requires temporal pain management

 Chronic pain: pain continues beyond the expected time of tissue healing; requires long-term pain management

Question 13

Types of pain (review) part 2

Nociceptive pain vs. non-nociceptive pain

Answer 13

1.) Nociceptive pain
 Somatic pain
 Visceral pain
 Inflammatory pain 
.
2.) Non-nociceptive pain
 Neuropathic pain
 Functional pain

Question 14

Types of pain (review). . . Nociceptive pain

Answer 14

Peripheral stimuli (temperature change, mechanical stimuli or chemical stimuli)

Question 15

Types of pain (review). . . Inflammatory pain

Answer 15

Tissue damage or inflammatory reactions

Question 16

Types of pain (review). . . Neuropathic pain

Answer 16

Central and peripheral nerve damage

Question 17

Types of pain (review). . . Functional pain

Answer 17

Normal nerve function but abnormal nerve conduction

Question 18

Types of neuropathic pain. . . 2 types

Answer 18

• Central neuropathic pain syndrome - Nerve damage on central nervous system
(brain/spinal cord)
• Peripheral neuropathic pain syndrome- Nerve damage on peripheral nervous system

Question 19

General treatment plans for neuropathic pain

Answer 19

• Treatment for the disease/condition that triggers or exacerbates neuropathic pain… e.g., diabetes
• Treatment for neuropathic pain. . . Pharmacotherapy/nonpharmacotherapy and Follow guideline and consider patients’ specific factors

Question 20

Treatment plan

• Treatment goals. . . Should be realistic!!!

Answer 20

• Medications are useful, but have finite benefits
• Realistic goals: e.g., walking with a granddaughter for 30
minutes every day, sleep at least 6 hours without pain, pain
scale of 3/10
• Unrealistic goal: e.g., pain free after initiation of medication
• There are multiple etiologies for neuropathic pain
• Multiple medications may need to be utilized

Question 21

Tips of pharmacotherapy for neuropathic pain

Answer 21

• Ideal analgesia = pain control + functional status
  .
• PK/PD and clinical factors to select appropriate pain medicine!… Pharmacokinetics: how a drug works in the body
   ADME
   Drug formulation: IR vs. ER
   Administration routes: PO vs. parenteral (PO: preferable.. Other routes: PR, IV, IM, transdermal)
   Distribution (Blood brain barrier)
   Metabolism (Hepatic function, Metabolites: e.g., nortriptyline from amitriptyline)
   Excretion/elimination (Renal function)
  Pharmacodynamics: how the body reacts to a drug –> Onset of action, Peak effect, Duration of action

Question 22

The pain pathway . . .

Answer 22

Question 23

Pharmacotherapy – overview . . .ascending pathway and descending pathways

Answer 23

Question 24

Treatment algorism for neuropathic pain

Answer 24

Question 25

``` Step 2: Initiation of therapy  Treatment for neuropathic pain Pharmacotherapy – start slow, go slow...  First-line agents (strong recommendations, equally effective): ```

Answer 25

Question 26

Step 2: Initiation of therapy |  Treatment for neuropathic pain . . .Gabapentin, pregabalin

Answer 26

 Block nerve impulse by binding Ca channels ↓Ca++ influx into presynaptic nerves ↓ release of excitatory neurotransmitters ↓ pain nerve firing  ADRs  Sedation, peripheral edema

Question 27

Mech, dose, side effects, PEARLS of Gabapentin, pregabalin

Answer 27

Question 28

Step 2: Initiation of therapy |  Treatment for neuropathic pain. . . SNRIs

Answer 28

 Block reuptake of NE and 5HT  Well-tolerated  Safer than TCAs (cardiotoxicity)  ADRs--> Sedation, GI ADRs (e.g., nausea), Insomnia, Headaches

Question 29

mech, dose, side effects, PEARLS of SNRIs . . . Venlafaxine (Effexor®), Duloxetine (Cymbalta®), Milnacipran (Savella®)

Answer 29

Question 30

Step 2: Initiation of therapy. . .Treatment for neuropathic pain . . . TCAs

Answer 30

 Effective to treat continuous burning pain  Block voltage-gated Na channels  Antagonize NMDA receptors  Block alpha adrenergic receptor  ADRs: Anticholinergic effects, Sedation, Orthostatic hypotension, Weight gain, Cardiotoxicity

Question 31

mech, dose, side effects, PEARLS of TCAs . . . Amitriptyline, Nortriptyline, Desipramine

Answer 31

Question 32

Step 2: Initiation of therapy  Treatment for neuropathic pain  Pharmacotherapy – start slow, go slow  Second-line agents (weak recommendations): . . .

Answer 32

Acute condition, exacerbation, neuropathic cancer pain, first-line agents/other pharmacotherapy options are not effective  Capsaicin topical  Lidocaine topical  Tramadol 200-400 mg/day

Question 33

Step 2: Initiation of therapy  Treatment for neuropathic pain  Pharmacotherapy  Other agents (weak/inconclusive recommendations): . .

Answer 33

 Antidepressants: SSRIs  Anticonvulsants (membrane stabilizers): carbamazepine, oxcarbazepine, lacosamide, lamotrigine, topiramate, valproic acid, zonisamide, etc.  Ketamine  Botulinum toxin A 50-200 units to the painful area every three months, specialist use  Opioids individual titration (Only when none worked)

Question 34

Step 2: Initiation of therapy  Treatment for neuropathic pain  Pharmacotherapy  Other agents (weak/inconclusive recommendations): Peripheral nerve injury results in abnormal accumulation of Na+ channels within neuron. . . what can you use for it?

Answer 34

Membrane stabilizers: carbamazepine, oxcarbazepine, lamotrigine, topiramate, valproic acid, etc.  Decreases presynaptic nerve cell depolarization by blocking Na+ channels  Decreases neuronal firing in the thalamus

Question 35

mech, dose, side effects, PEARLS of Membrane stabilizers: carbamazepine, oxcarbazepine, topiramate, valproic acid

Answer 35

Question 36

Step 2: Initiation of therapy |  Treatment for neuropathic pain. . . Nonpharmacotherapy

Answer 36

Question 37

Step 3: Reassessment of pain, treatment, and functional goals part 1 reassessment of pain and therapy (Pharmacotherapy/nonpharmacotherapy for neuropathic pain)

Answer 37

``` 1.) Pain  Quality and quantity of pain  Reset treatment goals 2.) Therapy  Pharmacotherapy/nonpharmacotherapy for neuropathic pain  Effective vs. not effective  Dose adjustment  Trial of different first-line agent(s) ```

Question 38

Step 3: Reassessment of pain, treatment, and functional goals part 2 Reassessment of Therapy . . .Pharmacotherapy/nonpharmacotherapy for concomitant disease states

Answer 38

 Obese patient – avoid valproic acid (weight gain), may be beneficial from topiramate (weight loss)  Patients with epilepsy – may be beneficial to use antiepileptic drugs, avoid bupropion (↓ seizure threshold)  Patients with migraine headache – topiramate may be beneficial  Patients with anxiety – gabapentin or pregabalin may be beneficial  Patients with depression – SNRIs may be beneficial  Patients with sleep issue: gabapentin, pregabalin, TCAs  Geriatric patients – avoid TCAs (Beers Criteria)

Question 39

Step 3: Reassessment of pain, treatment, and functional goals  Best medication to use is often based on concurrent comorbidities and/or not adding to side effects of medications currently used!  Common comorbidities includes:

Answer 39

```  Depression  Hypothyroidism  Hypogonadism  ↓ Vit D  Obesity  Sleep Apnea  PMH of PTSD  PMH of sexual or physical abuse ```

Question 40

Step 3: Reassessment of pain, treatment, and functional goals. . . Chart!! KNOW THIS

Answer 40

Question 41

Step 3: Reassessment of pain, treatment, and functional goals  When to determine the efficacy of medications for chronic pain?

Answer 41

 Observe patient’s condition for 4-6 weeks after initiation of medication  Observe for an additional two weeks after achieving maximum dosage