Clinical Analgesics Flashcards
WHO analgesic ladder
Principles of WHO analgesic ladder
By the clock
By the mouth
By the ladder
Individual dose titration
Use adjuvant drugs
Attential to detail
Limitations of WHO ladder
Developed for cancer pain
Evidence base?
What are adjuvants?
When should adujants be introduced?
What is the purpose of step 2?
Paracetamol side effects
LARB
Rash
Blood disorders
Acute pancreatitis
Liver + renal damage following overdose
Paracetamol interactions
Warfarin
NSAID properties
Analgesic
Anti-pyretic
Anti-inflammatory
NSAID mechanism of action
Inhibit COX responsible for arachidonic acid metabolism to cyclic endoperoxides
- Prevent formation of prostaglandins + thromboxanes
NSAID side effects
PGs involved in homeostasis + inflammation
GI Tract
- GIT erosion + ulceration
Renal
- reduce renal blood flow
- sodium, potassium + H20 retention
- acute liver failure
Respiratory
- bronchospasm
Haematological
- reduce platelet aggregation
- Aspirin = irreversible
- NSAIDs = reversible
Stratrgies to prevent GI side effects of NSAID
H2RAs
- competitively inhibit H2 receptor sites on gastric parietal cells to regulate gastric pH
Misoprostol
- synthetic prostaglandin E1 analogue
PPIs
- inhibit acid secretion by binding irreversibly to proton pumps
COX-2 specific inhibitors (COXIBs)
- Mechanism of action
- Effectiveness
- Side effects
Target PGs produced as result of pain + inflammation
e.g. celecoxib, etoricoxib, parecoxib
COXIBs are as effective as full dose NSAID comparators (but no better)
Side effects:
- COXIBs reduce, but do not eliminate, GI adverse effects
- Renal adverse effects are comparable with conventional NSAIDs
NSAID interactions
Increased bleeding
- anti-coagulants
- SSRIs
- Corticosteroids
Renal impairment
- Diuretics
- ACEi
Reduce elimination
- Lithium
- Methotrexate (MTX)
1st choice NSAID for healthy young adults
Low dose ibuprofen (<1200mg/day)
What oral NSAID should be prescribed for pts with CV risk factors?
Low-dose ibuprofen or Naproxen 1000mg/day
What should be prescribed with any NSAID to pts with high GI risk + long-term NSAID users?
PPI
Topical NSAIDs
Don’t apply to broken skin, mucous membranes or near eyes
Wash hands after use
Not used in pregnant women
Not used with oral NSAIDs
Unlikely of any interactions due to low plasma levels achieved
Rubifacient onsidered in pts @ risk of oral NSAID side effects
Cheaper than topical
Types of opioid
Name drugs for moderate pain + severe pain
Constipation is a major proble for patients taking Opioids.
What treatment options are there for this?
Patient controlled
- ROA
- Drug used
- Advantages + Disadvantages
What is epidural opioids?
Mixture of local anaesthetic + opioid
Commonly, fentanyl + bupivacaine
Respiratory depression uncommon due to lipophilicity of fentanyl
ADR = hypotension, infection + haematoma
What are syringe drivers?
Continuous subcutaneous infusion
Used when:
- patient cant take medicines by mouth
- bowel obstruction
- patient does not want to take regular oral medicines
Diamorphine is opioid of choice
How is opioids monitored?
Pulse
BP
Respiration rate
Pain
Oxygen Saturation
Sedation score
Opioid usage
Opioid side effects
What is Naloxone?
Opioid antagonist
Used to reverse effects of opioid especially when pts are experience severe respiratory depression
Higher affinity for opioid receptor than agonis
Short half life when given IV = repeat doses
Induce pain
Titrate gradually until effect is achieved
What is tramadol?
MOR agonist
Inhibits neurotransmitter noradrenaline uptake + 5-HT release
Causes pronounced side effects e.g. nausea + hallucinations
Less pronounced opioid side effects e.g. constipation
Tricyclic Antidepressants
Inhibit neuronal re-uptake of noradrenaline + serotonin
Use limited by ADR
ADR minimised by starting with low dose + small changes
Therapeutic dose 50 - 75 mg OD
e.g. amitriptyline + nortriptyline
Antiepileptic drugs
e.g. carbamazepine, phenytoin + sodium valproate
- Block voltage gated Na+ channels in peripheral neurones
- High incidence of ADR
- Limited license for neuropathic pain
e.g. gabapentin + pregabalin
- prevents voltage dependent Ca2+ channel activation in dorsal horn neurones
- No affect on sodium channels
- Cause fewer side effects + interactions
- licensed for neuropathic pain
Capsaicin
Used for postherpetic neuralgia, osteoarthritis + diabetic neuropathy
Causes burning sensation
Counselling on application
- pts need to wash hand after use before they start touching any sensitive part of their bodies e.g. eyes
Lidocaine 5% medicated plaster
For PHN
Apply up to 3 plasters for 12 hrs each day
