Analgesia and Adjuvants

Question 1

What types of pain are there?

Answer 1

Total pain - BPS and spiritual

Somatic

Visceral

Neuropathic - steady dysaesthetic, paroxysmal neuralgic

Incident (on specific action - not the same as breakthrough)

Acute and chronic

Cancer and non-cancer

Question 2

WHO analgesic ladder

Examples of adjuvants?

Answer 2

1. Non-opioid e.g. paracetamol ± adjuvant
2. • Weak opioid e.g. codeine ± adjuvant
3. • Stronger opioid e.g. morphine ± adjuvant

NSAIDs

AEDs

Corticosteroids

Anxiolytics

Anti-depressants

Muscle relaxants

Bisphosphonates

NMDA receptor blockers - e.g. Ketamine

Question 3

Paracetamol MOA

what effect does p450 have on it and why is this important in overdose?

Answer 3

Synthetic, centrally acting Non-opioid; reduces CNS PG production

10% converted to reactive metabolite that can cause liver damage; conjugated to glutathione and excreted. If OD - exceeed glutathione conjugation capacity therefore treat with N-acetylcysteine, a glutathione precursor to increase the pool

Question 4

Normal dose of morphine and MR variant?

How calculate brekathrough dose?

mu, kappa and lambda receptors

Answer 4

5mg 4hrly or 10-15mg in 12h MR (daily short release dose ÷ 2); NO CEILING dose, only SE preventing increasing dose further

1/6 of daily dose (so increases as daily dose increases) - therefore prescribe PRN dose as such (initialy = same as starting dose); keep accurate track to reassess daily dose

Question 5

Initial side effects of opioids

Ongoing

Rare but serious side-effects

Answer 5

• N,V,Drowsy, Delirium
• N+V, Constipation (Always prescribe with Laxative), Dry mouth
• Possible HP suppression and Immune suppression
• Resp depression
• Dependence
• neurotoxicity - myoclonus, allodynia, hallucinations

Question 6

Conversion ratio compared to oral morphine for:

Codeine

Tramadol

Oxycodone (better for bone)

fentanyl

ALfentanil

Buprenorphine

Diamorphine same as morphine but much more water soluble

Answer 6

Codeine - 1/10

Tramadol - 1/5 - 1/10

Oxycodone - 1.5-2

Fentanyl - 150

Alfentanil - 30

Buprenorphine - 60

Look in BNF for conversions

Question 7

Incident Pain

Old approach

New approach to treatment?

Answer 7

If predictable, e.g. painful dressing, give oral dose of oral morphine 30 min beforehand.

Mucosally absorbed opioid formulations - short duration of action that are rapidly effective e.g.

Fentanyl lozenges, buccal tablets, intranasal spray

Question 8

Which compounds can enhance sedative effects of opioids?

SSRIs and TCAs interact with tramadol…

Which opioids can’t be used in renal impairment?

Answer 8

Alcohol, anxiolytics, anti-psychotics

increased risk of convulsions

Morphine and codeine. Oxycodone can be used with caution while buprenorphine, fentanyl, alfentanil and methadone are ok with monitoring

Question 9

1. What Adjuvants suggested for bone pain?
2. Raised ICP?
3. Muscle spasm
4. Smooth muscle spasm

Answer 9

1. NSAIDs - naproxen, ibuprofen, diclofenac etc.; gastric protection required
2. High dose steroids and consider RT
3. DIazepam and baclofen
4. Hyoscine butylbromide

Question 10

First line agents used to treat neuropathic pain?

2nd line?

3rd line?

Answer 10

TCAs (SSRIs not recommended)

AEDs - carbamazepine, valproate, gabapentin, pregabalin - all cause NV, Dizzy etc. high therapeutic range, start low and titrate up

Tramadol, lidocaine