Neuropharmacology: Neurology, Pain And Analgesia Flashcards
What is the definition of pain
An unpleasant sensory and emotional experience associated with actual or potential tissue damage
What are the types of pain
- Nociceptive
- Neuropathic
- Psychogenic
What is a nociceptive pain
Caused by stimulation of intact primary afferent nerves responding to stimuli approachin or exceedin the harmful intestiny (nociceptors)
What is a neuropathic pain
Pain signal generated ectopically and often in the absence of ongoing noxious events by pathologic processes in the peripheral or central nervous system e.g diabetic get neuropathic pain
What is pyscgogenic pain
Pain with no apparent organic bassis/strict diagnostic criteria
What are pharmacological targets for pain
Source of pain Nociceptive substance (prostaglandins and cytokines) Nerve transmitter substance (serotonin) Modulators in spinal cord and brain Emotional reaction to pain
What is the WHO pain ladder
Step 1: non opiod drug e.g paracetamol
Step 2: weak opiod if pain insists e.g codeine with non opiod
Step 3: strong opiod e.g morphine with non opiod
What is the mechanism of paracetamol
Unknown but probably inhibits prostaglandins in CNS or modulates endogenous cannibinoids
Does paracetomal have anti inflammatory action
No
What is the mechanism of action of NSAIDs
Inhibitos of prostaglanding synthetase (cyclo-oxygenase)
What are the 2 types of cyclo-oxygenase
Cox 1
Cox 2
Where is cox 1 found
In the stomach it protects gastric mucosa
Where is cox 2 found
Inducible inflammatory found in the renal tract
Which enzyme inhibition are we intrested in for pain
Cox 2 that is involved in nociceptive pain
What are the common NSAID examples
Ibuprofen
Diclofenac
From the examples of NSAIDs which one is more stronger
Diclofenac
What drugs can NSAIDs interact with
Anti-platelets and anticoagulants- increased risk of bleeding
Nephrotoxins- increased risk of acute kidney injury
What are the side effects of NSAIDs
Cardiovascular risk
Renal dysfunction- AKI
Gastrointestinal bleding or gastritis
Hypersensitivity reaction: rashes, angioedema and bronchospasm
In patients with a previous or active peptic ulcer what should NSAIDs be prescribed with
PPI
What are examples of weak opiods
Codeine phosphate
Dihydrocodeine
What is the mechanism of action for opiods
Act on the CNS to alter the perecepton of pain
Do opiods have anti inflammatory affects
no
What are the adverse effects of opoids
Nausea
Constipation
Can codeine be used in children
No it is contraindicted
What is tramadol
An opiod analgesic
What is the mechanism of action of tramadol
Enhances 5HT and andregenic pathway
What are the side effects of tramadol
Subject to abuse
Respiratory Depression
Hypotension
Drowsiness
What are examples of strong opiods
Morphine
Fentanyl
Oxycodone
Pethidine
What are the mechanism of action of strong opiods
Act on mu and kappa receptors in the cns
Which group of patients should strong opiods be avoided in
Respiratory depression (type 2 respiratory failure) Hypotension Liver impairment (avoid in the elderly)
What are adjuvant agents
Drugs that are intended for indication other than pain but are analgesics in certain circumstances
At which step is adjuvant agents considered
Every step of the WHO ladder
What are examples of adjuvant agents
Tricyclic anti depressants e.g amitryptiline
Anti epileptic agents e.g pregabalin, gabapentin, carbamazepine
Anxiolytics: diazepam
What are the other modalities of pain management
Acunpuncture
Transcutaenous electrical nerve stimulation (TENS)
Topical anaesthesia
Nerve block epidural
In liver failure which drugs do we need to be aware of
NSAIDs- risk of bleeding
Opiods: can be slowly metabolised can precipitate encephalopathy in liver failure
In renal disease which drug do we need to be aware of
NSAID- can lead to further impairment
What is an issue with opiods
Dependence
