Drug Therapy of Neuropathic Pain Disorders

Question 1

Diabetic neuropathy
Fibromyalgia
Post-herpetic neuralgia
Trigeminal neuralgia

Answer 1

Distal, symmetrical

Widespread pain plus sleep and mood changes

Vesicular eruption of herpes zoster…allodynia

Unilateral sharp pain with hyperalgesia

Question 2

Duloxetine 
TCAs 
Gaba 
Pregablin
Carbamaze
Lidocaine

What are they used for

Answer 2

Diabetic, post-herpetic(off), fibro

Diabetic, post-herpetic (off)

POst-herpetic

Diabetic, post-herpetic, fibro

trigem

Post-herpetic

Question 3

Chronic pain mech

Answer 3

Lowered activation threshold due to increased expression of nociceptor or Na channels

SPontaneous action pontentials due to partial depolarization of affarents

Ephpatic coupling (co-activation of ajacent neurons due to demylinated axons)

Central sensitization (increased responsiveness of dorsla hron neurons to pain input)

Question 4

Mehc of dulooxetine for pain

Answer 4

Noradrenergic from brain to dorsla horn

NE release from presynaptic is enahnced by SNRIs

Bain is inhibite through interneurons

Occurs at dorsla horn of the spinal cord

NE is the most important part

Question 5

SNRIs type of releif

Answer 5

Partial and take 2-3 weeks to achieve full effedct

Question 6

TCA mech for pain

Answer 6

Same as SNRIs

Question 7

Amitrip vs. nor and when to take caution

Answer 7

Ami - most clinical trial date

Nor - fewer side effects

Elderly, cardiac dz, suicidal

Question 8

Gabapentinoids MOA

Answer 8

Binds the alpha2/delta subunit on Ca channes l

ct in the dorsla horn of the spinal cord…enhanced pain could be from increased expression of presynaptic Ca channels

These drugs may work to decrease expression or function of presynaptic Ca channels

Question 9

Gabapentin and pregablin

Elimin
Absorp
Bioavail

Answer 9

Both renal

Gaba oral is limited at high doses due to sautration of uptake in GI tract

Question 10

Alt to high-dose gaba

Answer 10

Administer more freqwuent
Switch to a different form
Switc hto pregablin

Question 11

SE of gaba/pregablin

Answer 11

Dizziness, somnolence, increase weight

Pregablin may give mild euphoria

Question 12

Mech of trigemi

Answer 12

Neuronal injury leads to neuronal hyperexcitability and demyelination

Low-intensity stimuli leads to ecxageraated response and co-activation of adjacent neurons

Question 13

MOA of carb

Answer 13

Blocks Na channels and suppresses hyperexcitabiity

Question 14

Development of post-herpetic neuralgia

Answer 14

Intial infection

Dormant virus in dorsla root ganglkion

Reactivation

Shingles

Viral rep can cause lasting damage/inflammation

Question 15

Diagnosis of post-herpetic neuralgia

Answer 15

Hyperalgesia or allodynia that lasts longer than 4 months

Question 16

Lidocaine MOA

Answer 16

Blocks Na channels and APs in sensory neruons of C and adelta fibers

Elevates threshold of activation for these neurons

Apply only to intact skin