Pharmacology Flashcards
What is the WHO pain ladder?
1) NSAID or paracetamol
2) Weak opioid
3) Strong opioid
What are the important brainstem regions for pain?
- periaqueductal grey (midbrain)
- locus ceruleus (pons)
- nucleus raphe magnus (medulla)
How can analegsia be caused in terms of the brain areas?
excitation of the periacqueductal grey causes analgesia using a pathway involving the nucleus raphe magnus or the locus coerulus
What is the mechanism of action of opioids?
- inhibition of opening of Ca2+ channels to suppress neurotransmitter release
- opening of K+ channels
- inhibition of adenylate cyclase
- mediated by GPCR opioid receptors
What are the major side-effects of opioids?
- apnoea
- orthostatic hypotension
- nausea
- vomiting
- constipation
- confusion
- hallucinations
- other cognitive disturbances
How do opioid agonists work?
analgesia through prolonged activation of mu-opiod receptors
What are the names of opiod agonists?
- Morphine: can be given by various routes
- Diamorphine: IV use for severe post-op pain
- Codeine: oral, can cause constipation as a side-effect
- Fentanyl
- Pethidine
- Buprenophine
- Tramadol
- Methadone
How do opioid antagonists work?
competitive antagonists at the mu-receptors eg Naloxone
How do NSAIDs work?
- inhibit the synthesis of prostaglandins by COX enzymes
- stop recruitment of leukocytes for inflammation
- suppress prostaglandins if they cross the BBB
What are the main NSAIDs?
aspirin, ibuprofen, naproxen, diclofenac and indometacin
What are the main conditions causing neuropathic pain?
- trigeminal neuralgia
- diabetic neuropathy
- post-herpetic neuralgia
- phantom limb pain
What is the action of gabapentin/pregabalin?
- anti-epileptics
- reduce the cell surface expression of a subunit of some voltage-gated Ca2+ channels
- reduces glutamate
What is the action of amitriptyline?
tricyclic antidepressants which decrease the reuptake of noradrenaline
What is the action of carbamazepine?
blocks voltage-activated Na+ channels that are upregulated in damaged nerve cells which control pain attacks in trigeminal neuralgia
What are the pain options for neuropathic pain?
- gabapentin and pregabalin
- amitriptyline
- carbamazepine
