Pharmacology Flashcards
what is the WHO analgesic ladder rungs
1 - NSAID (aspirin, diclofenac, naproxen, ibuprofen) or paracetamol
2 - Weak Opioid (codeine, tramadol)
3 - Strong Opioid (morphine, hydromorphone)
how is opioid action mediated
G protein coupled opioid receptors
what happens when a opioid binds with its receptor
Inhibition of opening of voltage-activated Ca2+ channels
Opening of K+ channels
what effect does Inhibition of opening of voltage-activated Ca2+ channels in opioids have
presynaptic effect – suppresses excitatory neurotransmitter release from nociceptor terminals
what effect does opening of potassium channel have in opioids
postsynaptic effect- suppresses excitation of projection neurones
what type of opioid receptor does agonist opioids work on
mainly through prolonged activation of μ-opioid receptors
features of morphine
- used in acute severe and chronic pain
- can be given IV, IM or SC
- oral for chronic pain
features of diamorphine
- more lipophilic than morphine
- rapid onset of action when administered IV
- used for post-operative pain
features of fentanyl
- given IV to provide analgesia in maintenance anaesthesia
- suitable for transdermal delivery in chronic pain states, but not in acute pain
features of buprenophine
- useful in chronic pain with patient-controlled injection systems
- partial agonist
- slow onset, but long duration of action
- can be given by injection, or sublingually
features of pethidine
- used in acute pain, particularly labour
- rapid onset of action when given IV, IM, or SC,
- short duration of action (no good for control of chronic pain)
- should not be used in conjunction with MAO inhibitors (excitement, convulsions, hyperthermia)
features of codeine and dihydrocodeine
- weaker opioids used in mild/moderate pain
- given orally, not IV
what opioid should not be used in epilepsy
tramadol
features of methadone
- given orally, long duration of action
- main use is to assist in withdrawal from ‘strong opioids’, such as heroin
what opioid is used in animals not humans
etorphine
what are the agonist opioid drugs
- morphine
- diamorphine
- fentanyl
- buprenophine
- pethidine
- codeine and dihydrocodeine
- tramadol
- methadone
what are the antagonists opioid drugs
naloxone
naltrexone
what are features of naloxone
- competitive antagonist at μ-receptors
- given IV (can give IM and SC if cannot give IV)
- short half life
what is naloxone used for
to reverse opioid toxicity (i.e. respiratory and/or neurological depression) associated with ‘strong opioid’ overdosage
what can naloxone cause in addicts
acute withdrawal response
how does naltrexone differ from naloxone
- longer half-life
how do NSAIDs work
inhibiting the synthesis and accumulation of prostaglandins by enzymes COX-1 and COX-2
in selective NSAIDs, what enzyme is blocked
just COX-2
why is paracetamol not classed as an NSAID
it lacks anti-inflammatory activity
what are conditions of neuropathic pain
trigeminal neuralgia
diabetic neuropathy
post-herpetic neuralgia
phantom limb pain
neuropathic pain responses to NSAIDs - true or false
false
- also rather insensitive to opioids
drugs (and their class) used for neuropathic pain
Gabapentin and Pregabalin
- anti-epileptics
Amitriptyline, nortryptiline and desipramine
- TCAs
Carbamazepine
what specific neuropathic conditions are gabapentin and pregabalin used for
gabapentin - migraine prophylaxis
pregabalin - painful diabetic neuropathy
how do TCAs work
decrease reuptake of noradrenaline
how does carbamazepine work
blocks subtypes of voltage-activated Na+ channel that are upregulated in damaged nerve cells
what is carbamazepine first line treatment for
Trigeminal neuralgia
