Exam 4: PAIN Flashcards
Neuropathic pain
pain caused by a lesion or disease of the somatosensory nervous system; damage to nerves
- increased nerve cell firing
- decreased inhibition of neuronal actvity d/t deafferenation and/or sensitization
Steps in noiciceptive pain
- stimulation
- transmission
- perception
- modulation
Myelinated vs. unmyelinated transmission
- myelinated - fast sharp pain
- unmyelinated - dull ache
Endogenous analgesic system
The opiate system
* NDMA receptors decrease the effects of opioates therefore, NDMA antags can enhance the actions of endogenous opiates
Role of NE and 5-HT neurons in pain
Inhibit pain transmission?
Spontaneous pain transmission
- contiuous - burning, throbbing, aching, shooting
- intermittent (episodic, paroxysmal) - shooting, stabbing, or electric shock-like
Hyperalgesia
increased pain form a stimulus that normally provokes pain
Allodynia
Pain d/t stimulus that does not normally provoke pain
Types of neuropathic pain
- spontaneous transmission (continuous and intermittent)
- hyperalgesia
- allodynia
Advantages of using TCAs for pain
- has a lot of data supporting use
- QD dosing
- conmittent insomnia and depression treatment
Disadvantages of using TCAs for paiin
- delayed onset
- anticholinergic
- cardiotoxic
General TCA dosing for pain
- Start: 25mg QHS
- MDD: 150mg/day
Advantages of using SNRIs for pain
- duloxetine FDA approved for PDN ad fibromylagia
- conmittant depression treatment
- favorable side effect profile
- milnacipran: can improve fatigue
PDN
painful diabetic neuropathy
PHN
post-herpetic neuralgia
LBP
q
lo back pain
Disadvantages of using SNRIs for pain
- Risk of serotonin syndrome with interacting meds
- Duloxetine: CI in hepatic impairment and ESRD (CrCl <30)
- Milnacipran: BID dosing, HTN ADR
SNRI dosing for pain
duloxetine
* start: 30mg QD
* MDD: 60mg BID
venlafaxine
* start: 37.5mg QD or BID
* MDD: 225mg TDD
milnacipran
* start: 12.5mg QD
* titrate over 1 week to 50mg BID
* MDD: 100mg BID
milacipran MOA
SNRI
* 3:1 NE:serotonin activity
* NMDA receptor binding
* lacks histaminic and muscarinic activity
Gabapentinoids MOA
Modulate hyperexcited neurons
Advantages of using gabapentin for pain
- low incidence of DDI and ADR
- FDA approved for PHN
Disadvantages of using gabapentin for pain
- mild CNS depression
- significant tox
Renally dose adjusted:
* CrCl 30-59 MDD: 700mg BID
* CrCl 15-29 MDD: 700mg QD
* CrCl 15 MDD: 300mg QD
* CrCl <15 MDD: proportinal to CrCl (if CrCl = 7.5 pt gets half of dose for CrCl 15)
Gabapentin formulations and dosing frequency
- PO capsule, tab, solution: TID
- PO tab ER: QD with evening meal
- PO enacarbil tab ER: BID
Advantages of using pregabalin for pain
- low incidence of DDI and ADR
- conmittant anxiety treatment
- FDA indicated for PDN, PHN, and fibromyalgia
Disadvantages of using pregabalin for pain
- DEA schedule V - dependency and euphoria
- mild CNS depression
- significant tox
- renal insufficiency
Pregabalin dosing for pain
- start: 150mg TDD taken BID or TID
- titrate every 3-7 days
- MDD: 600mg TDD
Advantages of using tramadol for pain
- less respiratory depression than opiates
- lower abuse potential than opiates
- treats neuropathic pain: inhibit reuptake of NE and 5-HT in CNS
Disadvantages of using tramadol for pain
DDI
* CBZ
* quinidine
* TCA
* SSRI
ADR
* dizziness
* GI upset
* constipation
* seizure risk
Tapentadol indication and MOA
neuropathic pain associated with diabetic peripheral neuropathy; DEA schedule II
MOA
* mu agonist
* NE reuptake inhibition
* weak anticholinergic effects
Tapentadol dosing
Q4-6 hrs
available as 50, 75, 100mg
Capsaicin MOA for pain
deplete and prevent re-accumulation of substance P in peripheral sensory neurons
FDA approved
Important counseling points for Qutenza capsaicin patches
- pre-treat with local anesthetic
- use up to 4 patches per application
- leave patches on for 60 miites
- do NOT use more than Q3 mo.
- patch strength is 8% (vs. normal OTC which is .025% or .25%
Lidocaine indications
PHN and topical anesthesia -> often used off label for pain
Quick onset of 5-10 min :)
1st line treatment for neuropathic pain
- TCA
- SNRI
- gabapentinoids
- topicals
2nd line treatment for neuropathic pain and when do we use 2nd line
exacerbation or inadequate response to first line
* tramadol
* combo of 1st line therapies
3rd line treatment for neuropathic pain and when do we use 3rd line
inadequate use response to 2nd line
* specialist referral first!
* SSRI/NMDA antag
* interventional therapies
4th line treatment for neuropathic pain and when do we use 4th line
inadequate response to 3rd line, 6+ months of neuropathic pain
* neuromodulation
5th line treatment for neuropathic pain and when do we use 5th line
inadequate response to 4th line
* 4-6 week trial of low-dose opiates with regular 3 mo. reviews
Is all diabetic neuropathy painful?
No
Painful diabetic neuropathy mechanism
- damage to peripheral nerves - hyperexcitability, spontaneous nerve impuses
- abnormal electrical connections
- coupling of sympathetic and afferent neurons and abnormal release of substance P from A fibers
- persistent nervve stimulation activates NDMA receptors
treatment for painful diabetic neuropathy
- gabapentinoids
- TCA
- SNRI
- sodium channel blockers (TEST QUESTION)
consider adding capsacin or switching between these classes before moving on to opiates
treatment for post-herpetic neuralgia
- TCAs
- antiepileptics (gabapentinoids, divalproex)
- tramadol
- lidocaine (best for focal)
- capsaicin
- opiates if all is fails
fibromyalgia
- enhanced sensitivity to stimuli (heat and cold)
- constant dull ache in all 4 quadrants
- often accompanied by fatigue and sleep disturbances
treatment for fibromyalgia
- CBT where appropriate
- duloxetine
- pregabalin
- tramadol
- milnaciprin is FDA approved but not really on guidelines
