Anaglesia neuropathic

Question 1

neuropathic pain guidance

Answer 1

first-line treatment*: amitriptyline, duloxetine, gabapentin or pregabalin

if the first-line drug treatment does not work try one of the other 3 drugs
in contrast to standard analgesics, drugs for neuropathic pain are typically used as monotherapy, i.e. if not working then drugs should be switched, not added

tramadol may be used as ‘rescue therapy’ for exacerbations of neuropathic pain

topical capsaicin may be used for localised neuropathic pain (e.g. post-herpetic neuralgia)
pain management clinics may be useful in patients with resistant problems

*please note that for some specific conditions the guidance may vary. For example carbamazepine is used first-line for trigeminal neuralgia

Question 2

causes of neuropathic pain

Answer 2

radiculopathy
Postherpetic neuralgia (post-shingles)
Trigeminal neuralgia
Nerve damage, including postoperative.
Pain because of cancer tumour infiltration.

Peripheral neuropathy:
A – Alcohol
B – B12 deficiency
C – Cancer and Chronic Kidney Disease
D – Diabetes and Drugs (e.g. amiodarone, metronidazole, cisplatin, phenytoin, isoniazid, nitrofurantoin)
E – Every vasculitis

Question 3

pathophysiology of neuropathic pain

Question 5

Name 2 SNRIs

Answer 5

Venlafaxine
Duloxetine

Question 6

Side effects SNRIs

Answer 6

include nausea/vomiting, sweating, loss of appetite, dizziness, headache, increase in suicidal thoughts, and sexual dysfunction.

Question 7

Complication SNRI

Answer 7

HTN

(Elevation of norepinephrine levels can sometimes cause anxiety, mildly elevated pulse, and elevated blood pressure. )(monitor before initiation and after titration)

Question 8

Name 3 TCAs

Answer 8

Imipramine
Clomipramine
Amitriptyline

lofepramine

Question 9

Mechanism TCAs

Answer 9

inhibit the reuptake of serotonin and noradrenaline.

Question 10

Side effects TCAs?

Answer 10

anticholinergic effects:
Can’t see (blurred vision)
Can’t pee (urinary retention)
Can’t spit (dry mouth)
Can’t shit (constipation)
Can’t sit for too long - postural hypotension

TCAs can cause overflow incontinence due to chronic urinary retention
Drowsiness
Postural hypotension

lengthening of QT interval

Question 11

How do gabapentin and pregabalin work?

Answer 11

Gabapentin acts a bit like GABA to inhibit neurotransmission. It binds with voltage sensitive calcium channels, where it prevents the inflow of Ca2+ and in doing so, inhibits NT release. This interferes with synaptic transmission and reduces neuronal excitability. Pregabalin is a structural analogue of gabapentin

Question 12

adverse effects gabapentin and pregabalin

Answer 12

: drowsiness, dizziness and ataxia (usually improve within a few weeks)

Question 13

interactions gabapentin and pregabalin

Answer 13

careful with other sedating drugs eg benzos

Question 14

why are TCAs used less than other antidepressants?

Answer 14

lost of side effects

HIGH MORTALITY IN OVERDOSE, AVOID PRESCRIBING IF SUICIDE RISK

Question 15

how does sudden TCA withdrawal present?

Answer 15

GI upset, neurological and influenza type symptoms and sleep disturbance

Question 16

interactions TCAs

Answer 16

risk of seretonin syndrome with MAOIs

Question 17

MoA SNRIs

Answer 17

inhibit Serotonin and noradrenaline re-uptake transporters on the presynaptic neuronal
Membrane - Prevents re-uptake and subsequent degradation of the monoamine neurotransmitters serotonin and noradrenaline from the synaptic cleft

Question 18

Indications SNRIs

Answer 18

Major depressive disorder
Neuropathic pain
Generalised anxiety disorder
Duloxetine is used for stress incontinence