Overview of analgesic drugs and their mechanisms of action - others Flashcards
Where are TRPV1 receptors found?
Highly expressed in sensory nerves throughout the CNS
When are TRPV1 receptors activated?
By inflammatory conditions e.g. temp, low pH, chemical mediators)
What is the role of a TRPV1 receptor when it is activated?
What causes its activation?
Gates cations leading to depolarisation of sensory nerves and excitatory mediator release
What happens when a TRPV1 receptor is agonised? What is the agonist?
Capsaicin stimulates, causing rapid desensitisation of the channel leading to a burning sensation followed by analgesia
In topical treatments with capsaicin how can we overcome the initial problematic burning sensation?
Treat with EMLA cream before application
What are the three actions of Tramadol?
A weak μ-opioid receptor agonist
A 5H-T releaser
A noradrenaline reuptake inhibitor
How is tramadol metabolised?
To O-desmethyltramadol, a much more potent opioid agonist
What pharmacokinetic feature of tramadol makes it less likely to be abused?
Long half life
What are the two actions of Tapentadol?
μ-opioid receptor agonist
noradrenaline reuptake inhibitor
How do tramdol and tapentadol reduce pain?
Increase the descending pain pathway (PAG–>NRM–> opioid pathways, 5H-T and NA)
An advantage of tapentadol?
More tolerable side effects profile than oxycodone and pethidine etc
How do alpha-2 adrenoceptor agonists cause anagesia?
Act on presynaptic receptors to reduce neurotransmitter release –> reduced excitatory transmitter release in the brain and spinal cord pathways
Why are alpha 2 adrenoceptor agonists not used in clinic?
Lack selectivity
What is allodynia?
Things that are not normally painful become painful
What causes neuropathic pain?
Results from damage to neural tissue
-trauma, herpes infection, diabetes, chemo, central pain following a stroke, HIV, alcoholism
Caused by peripheral and central sensitisation of pain pathways
