pain 1 Flashcards
What is the purpose of acute pain?
Protective mechanism
e.g. thermal burns
What are the types of pain?
(1) Nociceptive pain
(2) Neuropathic pain
What type of pain is caused by a tissue injury?
Nociceptive pain
How long does acute nociceptive pain last?
<3-6 months
Desirable
How long does chronic nociceptive pain last?
> 6 months
Undesirable
What is allodynia?
Pain after stimulation
Not normally painful
What is hyperalgesia?
Increased pain from a stimulus that normally causes pain
What is neuropathic pain?
Nerve injury
What are some conditions that are associated with neuropathic pain?
(1) Diabetic neuropathy
(2) Phantom limb pain
(3) Cancer pain
(4) Chemotherapy-induced peripheral neuropathy
(5) Postherapeutic neuralgia
How may neuropathic pain be described?
(1) Severe
(2) Sharp
(3) Burning
(4) Cold
(5) Numb
(6) Tingling
(7) Weakness
What is the pain pathway?
(1) Detection of pain in the periphery
(2) Transmission of pain signals from periphery to spinal cord
(3) Reception of signal by higher central brain centres
Describe the role of local neuronal circuits and descending inhibitory pathways from higher brain centres on signals
Signals are amplified or inhibited
Describe the myelination state of non-nociceptive Aß.
Myelinated
Describe the myelination state of nociceptive C.
Unmyelinated
What sensation do non-nociceptive Aß fibres produce? large
Touch + pressure
What sensation do nociceptive C fibres produce?
Dull + burning pain
What sensation do nociceptive A-delta produce?
Sharp pain
What are some inflammatory mediators of peripheral pain?
(1) Bradykinin
(2) Substance P
(3) ATP
(4) Protons
(5) Prostaglandins
- particularly PGE2 + PGF2
What is the role of bradykinin as an inflammatory mediator of peripheral pain?
Activates B2 receptors in nociceptive neurons + B1 receptors via a metabolite
What is the role of substance P as an inflammatory mediator of peripheral pain?
Activates NKA (neurokinin) receptors in nociceptive neurones
What is the role of ATP as an inflammatory mediator of peripheral pain?
Activates P2X3 receptors
What is the role of protons (H+) as an inflammatory mediator of peripheral pain?
Activate acid-sensing ion channels (ASICs)
What is the role of prostaglandins as an inflammatory mediator of peripheral pain?
PGE2 + PGF2
Greatly increase responses to bradykinin and 5-HT
Increase sensitisation
What are prostanoids?
Prostaglandins + thromboxane
Produced from precursors in cell membrane
What are some important neurotransmitters in hyperalgesia?
(1) Glutamate
(2) Substance P
(3) Nitric oxide
What factor limits non-opioids?
Ceiling effect
Dose above which there is no further pharmacological action
What is the mechanism of action of opiates?
Increase descending inhibitory pathways
Decrease neuropeptide release
What is acetylsalicylic acid?
Aspirin
Which analgesic is most appropriate for dysmenorrhoea?
Aspirin
Give some examples of indoles.
(1) Diclofenac
(2) Indomethacin
Give some examples of propionic acid derivatives.
(1) Ibuprofen
(2) Naproxen
(3) Ketoprofen
What is etoricoxib licensed for?
(1) Ankylosing spondylitis
(2) Osteoarthritis
(3) Rheumatoid arthritis
(4) Acute gout
What is celecoxib licensed for?
(1) Ankylosing spondylitis
(2) Osteoarthritis
(3) Rheumatoid arthritis
Why were rofecoxib and valdecoxib withdrawn?
Cardiovascular side effects
Why was lumiracoxib withdrawn?
Hepatotoxicity problems
What is nefopam?
Non-opioid
For persistent pain if NSAIDs or opioids are not suitable
Causes little-no respiratory depression
Can have sympathomimetic + antimuscarinic side effects
