Analgesia Flashcards
Drugs that reduce pain at the site of injury do so how?
Decreases sensitisation by blocking’s prostaglandin synthesis
Give a example of a drug that reduces pain at the site of injury?
NSAIDs
Drugs that reduce nerve conduction of pain do so how?
Block of voltage gates Na+ channels
Give an example of drugs that reduce the nerve conduction to reduce the perception of pain?
Lignocaine
List some drugs that reduce the synaptic transmission in the dorsal horn.
Opiods
Some antidepressants
List drugs which activate the descending inhibitory controls.
Opiods
Select tri-cyclic antidepressants
Which drugs target the ion channels that are unregulated in nerve damage?
Antiepileptics e.g. GABA pentinoids
List some common NSAIDs
Aspirin
Diclofenac
Ibuprofen
Naproxene
List some weak opiods
codeine
tramadol
dextropropoxyphene
List some strong opiods
Morphine
oxycodone
fentanyl
heroin
In supra spinal antinociception where do the neurones arise from?
Peraqueductal grey mater
Locus coeruleus
Nucleus Raphe Magnus
Where do neurones of the supra spinal anti-nociception project down to?
Posterior horn to the area where the 1st and 2nd order neurones of the spinothalamic tract synapse.
The supra spinal antinociception neurones release what into the synapse?
Noradrenaline 5 HT (Seretonin)
Noradrenaline and 5 HT have what affect of the spinothalamic tract?
Inhibits the release of Substance P from presynaptic build.
Prevents Depolarisation on the Second order neurone.
What affect does Noradrenaline and 5HT have on the interneurone located by the synaptic cleft of the 1st and 2nd order neurone?
Interneurone is activated and releases Enkephalin (Opiod)
What is the affect of Enkephalin?
Prevents depolarisation of the presynaptic bulb and the sport synaptic neurone.
What kind of receptors do opioids work on?
G protein Coupled Receptors
What is the affect of activating a opioid G protein coupled receptor?
Beta unit - Inhibition of Ca2+ channels suppress excitatory neurotransmitter release.
- opening K+ channels suppressing excitation by hyper-polarising the neurones.
Inhibiting adenyl cyclase - long term suppression
What are the different types of opioid receptors and what are there functions?
μ - most analgesic action and major sideaffects
δ - activation can be proconvulsant
k - Sedation dysphoria and hallucination
List the major respiratory side effects of Opioids.
Apnoea - medullary respiratory system becomes desensitised to CO2 levels
List the major cardiovascular side effects of Opioids
Orthostatic hypotension - reduced sympathetic tone and bradycardia
Histamine mediated dilation
List the major GI side effects of Opioids.
Nausea Vomiting Constipation
-acts on the CTZ
List the major CNS side effects of Opioids.
Confusion Euphoria Dysphoria hallucinations Dizziness Myoclonus Hyperalgesia
Morphine
Acute and Severe pain
Metaboised in liver
IV IM SC or oral
Diamorphine
Severe post operative pain
More lipophilic than morphine
Rapid onset when IV
Heroin
Codeine
Mild moderate pain
Anti diarrhoea Antitussive (prevent cough)
Oral
Fentanyl
75x more potent than morphine
IV to provide analgesia in maintenance anaesthesia
Transdermal or buccal in chronic pain
Pethidine
Acute pain especially labour
Rapid onset IV IM or SC - short duration
Should be given with MAO inhibitors
Buprenophine
Useful in chronic pain with patient controlled injection system
Slow onset but long duration of action
Tramadol
Weak μ agonist
Oral
Avoid in patients with epilepsy
Methadone
Chronic pain and cancer
Assisted withdrawal from heroine
Long duration of action
What is the purpose of Antagonist to Opioid receptors?
Used to reverse opioid toxicity
List some opioid antagonists
Naloxene
Naltrexone
Alvimopan
Naloxene
Incrementally IV IM or SC
Short half life - careful monitoring
Can induce acute withdrawal symptoms
Used in new borns with opioid toxicity
Naltrexone
Oral availability and longer half life
Alvimopan
No affect of CNS
Reduced GI affects of chronic opioid use.
NSAIDs
Prevent prostaglandin build up by inhibition of COX enzyme.
What drugs are used for neuropathic pain
Gabapentin
Pregablin
What is the action of gabapentin an pregablin?
Reduced voltage gated Ca2+ channel expression
Decreases neurotransmitter release
What is gabapentin used for?
Migraine prophylaxis
What is pregablin used for?
Useful in painful diabetic neuropathy
How do Tricyclic antidepressants like Amitriptyline work?
Decrease the re uptake of neurotransmitter noradrenaline
What is the first line drug for trigeminal neuralgia?
Carbamezapine
How does Carbamezapine work?
Block Na+ voltage gated ion channels
