EXAM 3 Chronic Pain Part 2 Dr. Thomason Flashcards
What is Neuropathic pain?
Pain of a lesion of disease affecting the somatosensory system
What are the most common causes of peripheral Neuropathy?
-Diabetic peripheral neuropathy (DPN)
-Postherpetic neuralgia (PHN)
also
-chemotherapy-induced
-HIV
-Phantom limb pain
-Postmastectomy pain
-Complex regional pain
-Trigeminal neuralgia
What are the most common causes of central Neuropathy?
-Multiple sclerosis
-Spinal cord injury
-Central post-stroke pain
-Parkinson disease
What are the first-line treatment options?
-TCA: nortriptyline, desipramine (secondary amine - not as sedating)
(amitriptyline and imipramine are tertiary amine -> amitriptyline metabolized to nortriptyline)
-duloxetine (SNRI, norepinephrine part helps with the pain), venlafaxine?
-gabapentin
-pregabalin
2nd line: combination of the first-line drugs
What is the dose of duloxetine that is helpful for neuropathic pain?
60 mg
above that is not helpful for neuropathic pain but seen for depression therapy
for venlafaxine = 225 mg
Which opioids might be used for neuropathic pain?
Methadone!!! in small doses
may be Tramadol
-> should not use opioids in neuropathy
When to consider Lidocaine for neuropathy?
peripheral neuropathy
also:
Topical Analgesics
Anticonvulsants
Tricyclic Antidepressants
Opioids
Which anticonvulsants are preferred in postherpetic neuralgia
pregabalin
gabapentin
Which anticonvulsants are preferred for diabetic neuropathy?
-carbamazepine
-phenytoin
-gabapentin
-lamotrigine
-pregabalin !!!
Which anticonvulsants are preferred for HIV-associated neuropathy and Central poststroke pain?
lamotrigine
Which anticonvulsants are preferred for trigeminal neuralgia?
-carbamazepine !!!
-lamotrigine
-oxcarbazepine
Non-pharmacolig treatment for neuropathic pain
-Neural blockade
-Neurolytic (kill the nerve)
-Stimulatory techniques
-medication pumps
What is the first approach in diabetic neuropathy?
control of the blood glucose level
What is the minimum dose of gabapentin to be effective for neuropathic pain?
1600 mg
Why may Tramadol not be the best choice?
because it needs to be metabolized in its active form by CYP2D6
patients who cant convert efficiently end up with an excess of the parent form (tramadol) -> more serotoninergic activity VS norepinephrine activity
serotonin side effects
-also seizure risk
What is the best way to prevent postherpatic neuropathy?
prevent herpes zoster infection with vaccines in patients over 50 (2 injections)
First-line treatment for postherpetic neuropathy
-TCA: nortriptyline
-Licoderm patch (local anesthetic)
2nd line:
-SNRI: duloxetine
-Anticonvulsants: Pregabalin and Gabapentin first -> Carbamazepine
What are the common side effects of gabapentin and pregabalin?
-weight gain
-peripheral edema (swelling in the legs)
-dose adjust if renal impaired
Clinical presentation in Fibromyalgia
PAIN:
-Allodynia: pain due to stimuli that should not cause pain
-Hyperalgesia: increased pain with an increase in the dose
-fatigue
-cognitive impairment (fibro fog)
-stiffness
-IBS, diarrhea
-cant do exercise, balance problems
-Restless leg syndrome (RLS)
-Hyperactive senses (noises, odor)
How is Fibromyalgia diagnosed?
-Widespread pain index WPI (0-19)
-Symptom severity scale SS (0-12)
WPI >7 and SS >5
or
WPI 3-6 and SS >9
Pharmacotherapy of Fibromyalgia
1st line: Antidepressant or Cyclobenzaprine (similar structure as TCA)
SNRI: duloxetine 20 -> 30 -> 60 mg
SSRI
TCA (more side effects)
2nd line: Anticonvulsant
Gabapentin and Pregabalin
muscle relaxant (helps with sleep)
dopamine agonist
do not use opioids (may make things worse)
Which drugs help for Restless leg syndrome in Fibromyalgia?
Dopamine agonist
Non-pharmacology treatment in fibromyalgia
-Not pacing activites when they dont have pain -> it may cause flair of pain at the next day
-exercise (if possible)
-sleep and eat well
-Cognitive Behavioral Therapy
How should Lidocaine patches be used
-can apply up to 3 patches per day (may use up to 4)
-direct over painful site
-12h on 12h off
Patient education with Capsaicin (topical anesthetic)
- for PHN or DPH
-onset at 14-28 days -> due to local depletion of substance P
-3-4x daily dosing
-Burning and local skin irritation -> correlates with to degree of subsequent anesthesia
How should Gabapentin and Pregabalin be discontinued?
taper off
-Pregabalin for at least a week
-Gabapentin may take longer to taper
-> to prevent withdrawal
Renal dosing required in CrCl < 30 mL/min!!!
What to monitor for Carbamazepine
-Na level
-WBC count
-LFT
-rash
Patient popualtion to avoid TCAs
patients over 65
bc of the side effects
-DO NOT USE within 14 days of MAOI use
-Acute recovery from MI - Cardiotoxic !!!
-suicidal ideation risk
Monitor TCAs
-get an EKG in patients over 40
-check BP
-it causes weight gain
Which TCAs have the least anticholinergic effects?
-Desipramine
-Nortriptyline
highest with Amitriptyline
Patient population to avoid with Venlafaxine
uncontrolled HTN
-need dose of 225 mg to be active -> not favorable bc it is not easy to come off the drug (discontinuation effects)
Cyclobenzaprine
used for Fibromyalgia if amitriptyline or nortriptyline is not tolerated
-not within 14 days of another MAOI
-helps with sleep -> give at night (sedation)
If an opioid is used for neuropathic, which one to pick?
Methadone
