Pain

Question 1

paracetamol

Answer 1

unknown mech; analgesia and anti-pyretic; not anti-inflammatory;

few SEs but easy OD

Question 2

NSAIDs

Answer 2

COX inhib » anti-inflam, anti-pyretic, and analgesia; -

SEs: GI, bleeding, bronchospasm (CI asthma), worsen renal failure, CHF, and HTN (fluid retention), oppose ACEI

interactions: anti-coags, SSRIs, MTX, lithium (TOX)

Question 3

Opioids

Answer 3

mu-receptor antagonists » decreased nerve activity;

SEs: constipation, urine retention, resp dep, itching, sedation, hypotension

weak: codeine, dihydrocodeine
strong: tramadol, morphine, oxy, fentanyl, buprenurphine

Question 4

ACD and TCA

Answer 4

AC = voltage Ca-channel inhib
TCA = NA/5HT reuptake inhibition

Question 5

Pain ladder

Answer 5

oral, regular (not PRN); post-op = top-down
adjuvants: TCA, CST, ACD, anti-spasm, AD, bisphos, nefopam

non-opioid: NSAID/paracetamol, can add adjuvant

weak opioid (mild-mod), may add non-opioid and adjuvant; e.g. codeine or cocodamol

strong opioid (mod-severe), may add non-opioid and adjuvant; e.g. morphine

Question 6

Neuropathic pain

Answer 6

TCA or anticonvulsant e.g. amitriptyline or carbamazepine/gabapentin/pregabalin

Question 7

Migraine

Answer 7

acute: triptans (5HT1-agonists Cause cerebral vasoconstriction and block trigeminal nerve transmission), poor oral absorption
CI: IHD, PVD, CVA Hx
step-wise: simple analgesia +/-anti-emetic, NSAID » diclofenac (PR) » triptans » ergotamine

prophylaxis: beta-blockers, 5HT2-antagonists (prevent vasodilatation and nerve sensitisation - block endothelial NO production), TCA
* e.g. pizotifen (5HT and H1 antagonist)