Wk 25 - Pain in Practice Flashcards
Give examples of observational changes for pain
- Pallor, tremor, tachycardia
- Grimacing, brow raising
- Altered gait, pacing
- Grunting, groaning
- Altered sleep
- Confusion, crying
What are the basic principles of prescribing analgesia?
- By mouth
- By clock
- By ladder
Outline the WHO analgesic ladder
- Step 1: non-opioid eg. paracetamol
- Step 2: weak opioid eg. codeine
- Step 3: Strong opioid: morphine
Give examples of mild to moderate pain analgesic options
- Paracetamol - inhibition of COX enzymes
- NSAIDs eg. ibuprofen + naproxen - non selective COX inhibitor
- Coxibs eg. celecoxib + etoricoxib - selective COX2 inhibitors
- Aspirin - blocks thromboxane production
Give examples of weak opioids to treat mild-to-moderate pain
- Codeine
- Dihydrocodeine
- Tramadol (inhibits NA + serotonin)
What is the choice of analgesic for under 16?
- 1st line (>3 months): paracetamol or ibuprofen
- 2nd line: Paracetamol + ibuprofen
- 3rd line: specialist advice
What is the choice of analgesics for adults?
- 1st line: Paracetamol 1g QDS or ibuprofen 400mg TDS (max 2.4g)
- 2nd line: paracetamol + ibuprofen
- 3rd line: Naproxen 250-500mg BD
- 4th line: weak opioid eg. codeine 60mg QDS w/ paracetamol + NSAIDs
What are things to consider when giving NSAIDs?
- Consider topical NSAIDs before oral for OA
- Think about CV, GI + renal issues
- Use lowest dose for shortest period
- Co-prescribe PPI
What is the dose for codeine?
- 30-60mg every 4hrs
- Max 240mg in 24hrs
What is the dose for dihydrocodeine?
- 30mg every 4-6hrs
- Max 240mg in 24hrs
What is the dose for tramadol?
- 50-100mg every 4hrs
- Max 400mg in 24 hrs
When should the dose be lowered when giving weak opioids?
- Elder
- CKD
- Hypothyroidism
- Adrenocortical insufficiency
What are the adverse effects of weak opioids?
- CNS depression (sedation)
- GI: nausea, vom + constipation
- Dependence: limit 3 days, caution w/ suspected dependence + w/drawal symptoms
- Tramadol: seizures, hallucinations, hyponatremia, hypoglycaemia
Give examples of drug interactions of weak opioids
- Caution w/ CNS depressants + alcohol
- MAOI - avoid during use + 2 weeks after stopping
- Tramadol: drugs that lower seizure threshold (TCA + carbamazepine), warfarin (raised INR) + SSRIs (inc seizure risk)
Give examples of strong opioids
- Morphine oral: IR + MR
- Morphine parenteral
- Diamorphine parenteral
Give examples of immediate release oral morphine
- Oramorph morphine sulphate oral solution (10mg/5ml)
- Oramorph conc morphine sulphate oral solution (20mg/ml)
- Sevredol tabs (10/20/50mg)
Give examples of 12hr MR oral morphine
- MST continus tabs
- Zomorph caps
Give an example of a 24hr MR oral morphine
MXL capsules
Outline the initiation for chronic pain
- 5-10mg every 4hrs of IR morphine
- Adjust: 1/3 to 1/2 of total daily dose every 24hrs
How do you convert to MR preparation?
- Calculate total daily dose
- Same total daily dose as MR product
- Calculate breakthrough
- Start 10-20mg BD + titrate whilst continuing IR when required
How do you calculate breakthrough dose?
1/6th - 1/10th of total daily dose
Outline the parenteral administration of opioids
- Patient unable to swallow
- DI dysfunction
- Morphine IM/SC every 4hrs
What happens if you convert morphine IR to SC/IM?
Give 50% of dose same feq.
What happens if you convert morphine MR to SC/IM?
Give 50% of total daily dose - divide + administer every 4hrs
What are the adverse effects of opioid analgesia?
- Euphoria
- Drowsiness
- Nausea + vom
- Constipation
- Tolerance
- Addiction
- Respiratory depression
Oxycodone
- Semi-synthetic analogue of morphine
- Partly metabolised to oxymorphone
- Caution in hepatic impairment
- Renal impairment: Clearance of drug + metabolites red
- 2nd line, difficult pain, mild renal impairment
Fentanyl patch
- Semi-synthetic analogue of morphine
- Norfentanyl (inactive) metabolite
- Safe for renal impairment
- 2nd line, stable pain, concordance, constipation, renal impairment
Outline how to apply fentanyl patches
- Apply to non-hairy, non-irritated skin of torso or upper arm
- Skin cleaned w/ water only + skin dry
- Patch cut or damaged should not be used
- Applied for 72hrs + new patch applied to diff. skin
- Same brand
What are things to remember when giving fentanyl patches?
- Evaluation of analgesic effect shouldn’t be made before system has been worn for 24hrs
- Previous analgesic therapy phased out gradually
- Close monitoring
- Dose adjusted 48-72 hrs intervals in steps of 12-25mcg/hr
How is the breakthrough dose usually given when using fentanyl patches?
Morphine sol or oxycodone sol
Alfentanil
- Synthetic derivative of fentanyl (more rapid onset + shorter duration of action)
- 1/4 potency of fentanyl
- 10x more potent than SC diamorphine
- Injection
- 2nd line, renal failure
Buprenorphine patch
- Semi-synthetic analogue of morphine
- Metabolites: norbuprenorphine
- Potency: transect (low dose strong opioid) + buTrans (weak opioid)
- Duration: transect 4 days + butrans 7 days
- 2nd line, stable pain, concordance + low dose
Hydromorphone
- Semi-synthetic analogue of morphine
- Metabolites: H3G
- Renal impairment: clearance unchanged but metabolite accumulate
- 2nd line, mild-mod renal impairment
What should you remember when increasing opioid dose?
Not >50% higher than previous dose
What is neuropathic pain?
Characterised by aetiologies affecting NS
Nerve lesion related to:
- CNS (traumatic spinal cord injury, central post stroke pain)
- PNS (diabetic polyneuropathy, carpal tunnel syndrome + HIV sensory neuropathy)
How does neuropathic pain present as?
- Burning constant pain w/ stabbing paroxysmal attacks
- Hypersensitivity on clinical examination
How does neuropathic pain respond to opioids + anti-inflammatory?
Poorly responsive
What is the neuropathic pain oral analgesic ladder?
- 1st line: tricyclic antidepressants or anti epileptics (1 drug)
- 2nd line: tricyclic antidepressants + antiepileptics (combination)
- 3rd line: strong opioids + invasive procedure
Amitriptyline
- Analgesic
- 3-7 days til effect
- S/e: antimuscarinic
- Dose: 10mg nocte, upto 75mg nocte
- Alts: imipramine + nortriptyline
What is the mechanism of action of gabapentin + pregablin?
- Chemical analogue of GABA
- Binds to CNS, interact w/ alpha 2 delta calcium channels in CNS
- Anticonvulsants for neuropathic pain
- Caution in renal impairment
- S/e: drowsy/dizzy
Gabapentin pharmacokinetics
Requires slow individual titration (100mg nocte, max 3.6g daily)
Pregabalin pharmacokinetics
- Linear pharmacokinetic profile
- 90% bioavailability
- Onset of pain-relief = quicker
Duloxetine
- Selective inhibitor of serotonin + NA
- Central pain inhibitory actions
- Act in synergistic manner to red transmission of pain signals from periphery to CNS
- For diabetic neuropathy: 60mg daily upto 120mg
- S/e: nausea, dry mouth, insomnia, constipation
What is the NICE recommendations on initial pharmacotherapy for neuropathic pain?
- Offer: amitriptyline, duloxetine, gabapentin or pregabalin
- Tramadol for acute rescue
- Capsaicin cream if oral agent unsuitable
What is used for trigeminal neuralgia?
Carbamazepine
What are the other options for neuropathic pain?
- Ketamine
- Methadone
Ketamine
- Most potent NMDA receptor channel blocker
- Indication: dissociative anaesthetic
- S.e: HT, tachycardia, hallucinations, urological complications
- Red dose if opioid co-prescribed
Methadone
- Mu + delta agonist
- NMDA receptor channel blocker
- Accumulates in tissue
- Safe in renal + hepatic impairment
- Stop other opioids
Give examples of other adjuvant therapies
- Corticosteroids: inflammatory conditions, cancer pain
- Bone pain: bisphosphonates, calcitonin, radiopharmaceuticals
- Musculoskeletal: muscle relaxants + benzodiazepines
- Bowel obstructions: octreotide + hyoscine
Give examples of non-drug pain relief
- Apply heat + cold
- Massage
- TENS
- Radiotherapy
- Acupuncture
- Psychological therapies
