Analgesia nociceptive Flashcards
what are the four components of pain
- Physical pain
- Psychological pain
- Social pain
- Spiritual pain
what are the steps of the WHO analgesic ladder
Step 1: non-opioids (eg paracetamol or NSAIDS) +/- adjuvants
Step 2: weak opioids (eg codeine, dihydrocodeine or tramadol) +/- adjuvants
Step 3: Strong opioid (e.g morphine, oxycodone, methadone, buprenorphine, fentanyl) and non-opiod +/- adjuvants
What are the 5 key principles of the WHO analgesic ladder
By mouth - PO where possible
By the clock - regular intervals
For the individual - according to pain character, type and intensity
By the ladder - follow ladder and start with lowest doses and titrate according to response
Attention to detail
what are some non-pharmacological methods of pain management
education, explanation and reassurance, physiotherapy, electrotherapy, mindfulness, or acupuncture
rung 1/3 of WHO analgesic ladder
Step 1: Consider regular paracetamol use
0.5g – 1g every 4-6 hours; maximum 4g daily
step 2: Add an NSAID (+/- PPI)
Typical drug dosing for (oral) ibuprofen:
Mild to moderate pain: initially 300-400mg 3-4 times a day; increased up to 600mg 4 times a day if necessary; maintenance 200-400mg three times a day
rung 2/3 of WHO analgesic ladder
Step 3: Add codeine/co-codamol
codeine Mild to moderate pain: 30-60mg every 4 hours as required
Step 4: Stop codeine/co-codamol & trial tramadol
Moderate to severe acute pain: initially 100mg, then 50-100mg every 4-6 hours; usual maximum 400mg/24 hours
rung 3/3 WHO analesic ladder
Step 6: Stop tramadol & start morphine
Before prescribing any strong opiate, consider ABC:
Start Antiemetic metoclopramide
Consider Breakthrough pain
Prescribe laxatives for Constipation senna
To titrate morphine:
1. Prescribe the dose on a regular basis/PRN every four hours eg 5mg
2. Reassess after 24 hours, if pain free the total dose that has been administered over the past 24
hours should be added up and converted into a twice-daily sustained/modified release
(SR/MR) dose by dividing the total 24 hour dose by two.
3. If the patient is still reporting pain first confirm adherence and then consider increasing
the dose prescribed and re-assessing after another 24 hours.
Once their MR has been established, add morphine for breakthorugh pain to take ‘PRN’. Commonly 1/10th to 1/6th of
the equivalent total daily dose of the drug every 4 hours PRN
Step 7: Refer to pain management specialists
how to convert from morphine in mg to oxycodone in mg
divide by 2!
why does acetylcysteine work for paracetamol overdose
Acetylcysteine (treatment for overdose) is a glutathione precursor
Cytochrome P450 metabolises it into NAPQI (toxic metabolite) which is conjugated with glutathione before elimination.
which patients should avoid paracetamol
paracetamol should be reduced in ppl with liver failure (due to increased NAPQI production eg in excess alcohol intake, OR reduced glutathione stores (malnutrition, low body weight, severe hepatic impairment) - this is particularly important for IV infusion paracetamol
interactions paracetamol
cytochrome p40 inducers eg phenytoin, carbamazepine increase the rate of NAPQI production and risk of liver toxicity after paracetamol overdose
dosing paracetamol
0.5-1g PO 4-6 hourly (maximum 4g/24 hours)
interactions NSAIDs
many drugs when combined, increase the risk of NSAID adverse effects. Eg gastric ulceration: aspirin and corticosteroids. Gastric bleeding: anticoagulants, SSRIs, venlafaxine. RENAL IMPAIR: ACEi, diuretics. NSAIDs increase the risk of bleeding with warfarin and reduce the therapeutic effects of anti-HTNs and diuretics
Adverse effects NSAIDs
COX-1 inhibition
Peptic ulceration (decreased PGE2),
Bleeding (decreased TXA2), this is more prominent in selective COX-1 inhibitors
Renal impairment (decreased PGE2 and PGI1)
COX-2 inhibition
Increased risk of cardiovascular events (decreased PGI1) this is more prominent in selective COX-2 inhibitors as TXA from COX-1 is unopposed whilst PGI2 is suppressed
LOX upregulated
Importantly, if the COX system is being inhibited, there is more arachidonic acid to be directed to LOX - this makes leukotrienes and can ppt bronchospasm in asthmatics! Caution!
name some COX-1 selective NSAIDs
Ketorolac
Indomethacin
Low dose aspirin
name some non-selective NSAIDS
Ibuprofen
Naproxen
name some COX-2 selective NSAIDs
Diclofenac
Etoricoxib
contraindications to NSAIDs
active bleeding, thrombocytopenia, peptic ulcer, history of adverse effects with NSAIDs, severe heart failure, varicella infection, severe renal impairment eGFR<40, liver failure, asthma, uncontrolled HTN
dosing ibruprofen
Ibuprofen 300-400mg tds-qds
Normal tablet is 200mg but check as there are many different types
what is the risk NSAIDs asthma
Importantly, if the COX system is being inhibited, there is more arachidonic acid to be directed to LOX - this makes leukotrienes and can ppt bronchospasm in asthmatics! Caution!
name some weak opioids
codeine, dihydrocodeine, tramadol
how does codeine work?
codeine and dihydrocodeine are metabolised in the liver to produce small amounts of morphine
why is tramadol unique compared to other opioids
Tramadol is a synthetic analogue of codeine. Tramadol, unlike other opioids, also acts on serotonergic and adrenergic pathways where it is thought to act as a serotonin and noradrenaline reuptake inhibitor- contributes to analgesic effect
It can be used for both nociceptive and neuropathic pain. Therefore if responsive, consider whether the pain is truly nociceptive.
adverse effects opioids
nausea, constipation, dizziness, drowsiness, neurological and respiratory depression when taken in overdose.
what drugs should tramadol be avoided with
try to avoid other sedating drugs eg benzodiazepines, antipsychotics, TCA. don’t give tramadol with other drugs that lower seizure threshold eg SSRIs and TCAs. Tramadol can also cause serotonin syndrome especially when combined with other serotonergic drugs eg many antidepressants
what specific condition must tramadol be avoided in
Tramadol lowers seizure threshold so avoid in epilepsy
what should be prescribed alongside a weak opioid
advise the person of the risks of constipation, and prescribe a stimulant laxative (such as senna or dantron-containing laxative) at the time of first prescription. Just think that opioids turn the gut off so you need to turn it back on with a stimulant laxative
examples of strong opioids
morphine and oxycodone
indications strong opioids
Rapid relief of acute severe pain eg post-operative or pain associated with MI
Chronic pain where rest of WHO ladder is exhausted
Relief of breathlessness in EOLC
To relieve breathlessness and anxiety in acute pulmonary oedema , alongside oxygen, furosemide and nitrates
moa opioids
Activation of opioid mu receptors in the CNS. activation of these G coupled receptors reduces neuronal excitability and pain transmission.
In the medulla they blunt the response to hypoxia and hypercapnia, reducing respiratory drive and breathlessness. By relieving pain, breathless and associated anxiety, opioids reduce sympathetic nervous system activity. The theory extends that in Mi and acute pulmonary oedema they may decrease cardiac work and oxygen demand,a s wella s relieving symptoms
why do opiods cause nausea and vomiting? management?
stimulation of CTZ
Haloperidol, metoclopramide or levomepromazine
how does opioid overdose present?
neurological depression and drowsiness, respiratory depression and associated cyanosis (blue lips and peripheries) , pupil constriction, flushing of the skin, itching,
how does opioid withdrawal present?
Opioid withdrawal is the opposite of the opioid effects
anxiety, pain, breathlessness, pupil dilation, skin is cool and dry with piloerection pt has gone “cold turkey” and appears like a “cold turkey”
cautions strong opioids
rely on liver and kidneys for excretion so dose reduce in renal and hepatic impairment and in the elderly. Do not give in resp failure (unless expert guidance in palliative care), avoid opioids in biliary colic as they may cause spasm of sphincter of oddi and make pain worse.
interactions strong opioids
dont use with other sedating drugs eg antipsychotics, benzodiazepines, TCA
ABC of strong opioid prescribing
Start Antiemetic (metoclopramide)
Consider Breakthrough pain
Prescribe laxatives for Constipation (stimulant - senna)
?opioid overdose, what do you prescribe?
Naloxone
small incremental dose 200-400 mcg IV every 2-3 minutes until satisfactory reversal has been achieved. In patients who develop[ opioid toxicity in the context of chronic use (especially in palliative care) - smaller incremental doses should be used e.g. 40-100mcg.
why is it important to monitor aptients that you needed to give naloxone to?
closely monitor patient fot at least an hour. This is beacuse the action of naloxone (20-60 mins) is shorter than most opioids so opioid toxicity can reoccur
MoA naloxone
binds to opioid receptorsa s a competitive antagonist. It has little to no effect in the absence of exogenous opioids.
How do you titrate morphine
To titrate morphine:
1. Prescribe the dose on a regular basis/PRN every four hours eg 5mg oromorph
2. Reassess after 24 hours, if pain free the total dose that has been administered over the past 24
hours should be added up and converted into a twice-daily sustained/modified release
(SR/MR) dose by dividing the total 24 hour dose by two.
3. If the patient is still reporting pain first confirm adherence and then consider increasing
the dose prescribed and re-assessing after another 24 hours.
How do you prescribe for breakthorugh pain- morphine?
Once their MR has been established, add morphine for breakthorugh pain to take ‘PRN’. Commonly 1/10th to 1/6th of
the equivalent total daily dose of the drug every 4 hours PRN
NSAIDS and renal issues?
dont use if eGFR <40 !!!!
NSAID lowest risk of cardiac events?
naproxen
what to do if renal impairment and on morphine for pain relief and showing signs of toxicity? how to control pain
Because morphine is renally excreted, it is generally avoided in patients with renal impairment. Oxycodone is typically used as a substitute as it is metabolised by the liver.
eg if were on morphine 30mg bd
switch to oxycodone 15mg bd
