Analgesia and Palliative Care Flashcards
WHO analgesic ladder
Non opioids (NSAIDs and paracetamol)
Weak opioids - codeine and tramadol (+/-adjuvants)
Strong opioids - morphine, fentanyl, oxycodone (+/-adjuvants)
Adjuvants = TCAs, steroids, bisphosphantes, muscle relaxants
Prescribing pain relief
Oral administration where possible
Analgesia @ regular intervals
Dosing adapted to pt increase the dose if breakthrough pain!!
Paracetamol MOA
Not fully understood believed to be due to reducing prostaglandin synthesis from arachdonic acid. Peripherally blocks pain impulses to reduce signalling and inhibit hypothalamic heat regulation
Max dose of paracetamol
1g QDS
Paracetamol OD
Can lead to thrombocytopenia and more importantly acute liver failure
<150mg/kg = unlikely to causes significant damage >250mg/kg = significant risk
NSAIDs MOA
Inhibit the COX enzymes which convert arachdonic acid to prostaglandins and thromboxanes. Reduce prostaglandin levels to analgesic, vasodilation and anti-pyretic effects
CI NSAIDs
Liver or renal impairement
PMHx of PUD or GI bleed
Asthmatic
IHD
SE of NSAIDs
GI bleed due to reduced prostaglandins leads to high acid levels and inadequate mucus protection. Especially COX-1 selective ibuprofen and naproxen (Increase with SSRIs)
AKI cause vasoconstriction of the afferent arteriole, this is due to the loss of the normal vasodilator effects of prostoglandins
Bronchospasm due to compensatory increase in leukotriene production which cause bronchoconstriction
Increased cardiac vascular risk with COX-1 selective drugs such as celecoxib and rofetecoxib
Inhibit bone healing
Codeine phosphate MOA
Metabolised to morphine by CYP2D6 enzymes. It acts a partial agonist on the u opiod receptor expressed throughout the CNS and PNS. This leads to closure of N-type voltage depends Ca2+ and opening of Ca2+ dependent inwards K+ channels.
This = membrane hyperpolarisation, prolonging action potentials and inhibiting nociceptive pathways in the CNS
SE codeine
Constipation and nausea
Risk of opiate toxicity esp in those with renal failure
Resp depression and hypotension
CI codeine
COPD, acute asthma, hypotension, shock, hepatic and renal impairment
Tramadol
Similar MOA to codeine but acts on muscarinic and serotonin receptors. Lower incidence of constipation, increased risk of serotonin syndrome if combined with SSRI’s and SNRI’s
Strong opiods
Morphine - PO,IV, SC, PCA, - oromorph PO, MST
Fentanyl - patch
Diamorphine IV/SC
Oxycodone - SC, IV, PO
MOA morphine
Full agonist at the u opiod receptor. leads to closure of the N type voltage dependent Ca2+ channels opening of Ca2+ dependent inward K+ channels leads to a pre synaptic inhibition of neurotransmitters due to membrane hyperpolarisation
SE morphine
Constipation and nausea Pruritus Urinary retention and euphoria Hypotension Bronchospasm Respiratory depression
Opiate OD
PC myoclonic jerks, bilateral pin point pupils, reduced respiratory rate, hallucinations and confusion. Increased risk if alcohol misuse aswell
IV naloxone stat!
Safe prescribing of opioids
Always prescribe with an antiemetic and laxitive
PRN breakthrough is 1/6th-1/10th of daily dose
Metabolised @ liver review dose regularly for efficacy and side effects
In renal failure/AKI opioids can accumulate so beware
Interactions of morphine
CNS depressants such as alcohol, sedatives and hypnotics increase the risk of resp depression
Acute severe pain
Burns, #NOF, amputation IV 2mg rapid acting and strong enough to make patient comfortable . Titrate dose up to symptom relief. Crucial to monitor resp rate and BP!
Give with metaclomprimide and a laxative
Post op analgesia
Combination of opiod and non opioids
IV via PCA. Allows pt to control their pain via a button set to deliver a pre set bolus. There is then a fixed lock out time until another can be delivered
Oral analgesia - paracetamol, NSAIDs and MST
Epidural increased side effect profile - pruritus, urinary retention and N/V. Small change of haematoma, infection etc