Pain-Killers
WHO pain ladder
Adjuvants: anticonvulsants (neuropathic), TCAs
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Non-opioid (aspirin, paracetamol, NSAID) ± adjuvant
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Opioid for mild/moderate pain (Co-codamo) ± Non-opioid ± Adjuvant
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Opioid
for moderate/severe pain (morphine, diamorphine, fentanyl, oxycodone,
hydromorphone) ± Non-opioid ± Adjuvant. Oral morphine is drug
of choice.
Morphine
Morphine is available in liquid, tablet, normal and controlled release
preparations. Oral morphine should be given every 4 hours.
Titrating morphine:
Starting dose is 2.5-10mg 4 hourly (reduce in elderly or impaired renal function).
Breakthrough
pain:
Pain which occurs between regular doses: give a dose equivalent to
the 4 hourly dose. Normal regime continued even if breakthrough dose taken. After 24 hours the
new dose of morphine is the net morphine in that time divided by 6 (if given 6 times a day), and
the rescue doses increased accordingly.
Maintenance
: Once dose titrated, patient may prefer convenience of controlled release
perparation of morphine. The 12 hourly controlled release (MST Slow Release,
tradename zomorph) is the 24 hour dose divided by 2.
Adverse Effects:
Nausea/vomiting, hallucinations, itching, tolerance/dependence (rare if true pain)
Nausea:
Give morphine with an anti-emetic e.g. cyclizine 50mg PO/IV/IM TDS. Maximum 150mg in 24h.
Oxycodone
At higher doses morphine has poor solubility & oxycodone is preferred.
Dose:
Divide morphine dose by 3
Codeine Phosphate
Uses:
Mild to moderate pain, diarrhoea
Dose:
Oral 30-60mg every 4h
Adverse Effects/Contraindications:
see morphine
Co-codamol x/Y
Co-codamol is combination of codeine/paracetamol, where x is mg of codeine phosphate, and y is mg of paracetamol.
Dose:
Often 30/500 for moderate pain
NSAIDs
Mechanism:
Pain relief, anti-inflammatory
Examples
Diclofenac:
Pain/inflammation in rheumatoid arthritis, acute gout, post-op
Ibuprofen:
“”, fever/pain in children, dysmenorrhoea, migraine. 1.2-1,8g daily in divided doses
Adverse Effects
GI discomfort/bleeding (should take with meals), hypersensitivity, renal failure
Contraindications:
Asthma, hypersensitivity to any NSAID, severe heart failure. COX2s are
CI in some CVS diseases now. NSAIDs may interfere with renal function,
fluid retention.
Aspirin
Mechanism:
COX inhibitor, an NSAID. Aniplatelet: stops aggregation of platelets.
Uses
Pain relief:
300-900mg every 4-6 h, max 4g daily. Alternative: paracetamol
CVS disease as an antiplatelet:
75mg daily. Alternative: clopidogrel
Adverse Effects
GI bleeding/irritation (so take after food), bronchospasm
Contraindications:
Reyes's syndrome, Children < 16y, breast feeding, Hypersensitivity,
Previous reaction to an NSAID e.g. asthma/angiodema
Paracetamol
Mechanism:
COX inhibition. It is not an NSAID: does not irritate the lining of the
stomach, affect blood coagulation as much as NSAIDs, or affect function
of the kidneys.
Uses:
Mild to moderate pain, pyrexia
Dose: 0.5-1g every 4-6h to a max 4g daily. Can also be given (rarely) as IV infusion, rectal
Adverse Effects:
Liver damage in overdose. Rashes, blood disorders (e.g. thrombocytopenia).
