pharmacology of pain management Flashcards
what are the two types of pain?
nociceptive and neuropathic
what is nociceptive pain
caused by tissue damage, generally time-linted
what is neuropathic pain
caused by damage to neurones, tends to be chronic
nociceptive pain is relieved by?
analgesics specifically NSAIDs and opioids
what does NSAIDs stand for
non-steroidal anti-inflammatory drugs
what are the four main properties of NSAIDs
- anti-inflammation
- anti-pyretic: reduces fever
- analgesic: rapid pain relief via CNS and PNS
- anti-coagulant
how do NSAIDs work
effects are achieved by preventing the breakdown of arachidonic acid by inhibiting cyclo-oxygenase (COX enzymes). This decreases the production of prostaglandins and thromboxane. By preventing prostaglandin production the NSAID reduces neuronal firing decreasing pain sensation
what are the characteristics of opioids
- analgesia
- anaesthesia
- antitussive effects: decrease cough reflex
- antidiarrheal effects
how do opioids reduce neuronal activity in the CNS and PNS
Opioids reduce neuronal activity in the CNS and PNS by binding to the opioid receptors:
- Decreased opening of voltage-dependent Ca2+ channels
- Increased K+ outflow
- Decreased Ca2+ is release from intracellular stores
- Decreased exocytosis of transmitter vesicles
paracetamol is similar to what type of analgesic
NSAIDs
what are the properties of paracetamol
- very good analgesic
- very good antipyretic
has very little anti-inflammatory effects
which type of pain is harder to treat
neuropathic
what are the types of drugs that treat neuropathic pain
- tri-cyclic antidepressants
2. antiepileptics
how do tri-cyclic antidepressants work
block the reuptake of both 5HT (serotonin) and noradrenaline.
- By increasing 5HT and NA they increase the activity in the descending pathways which blocks transmission. They can act in a positive way.
- Block adrenoreceptors, histamine receptors and muscarinic receptors. Antihistamines can block inflammatory responses and blocking adrenoreceptors helps with pain management
how do antiepileptics work
Act to reduce the hyperactivity in the neurones that is associated with neuropathic pain.
- Gabapentin: block voltage dependent calcium channels which would decrease hyperactivity
- Carbamazepine: can block voltage dependent sodium channels which also decrease neuronal activity
how do anaesthetics work
enter the cell through the membrane in an unionised form and become ionised in the intracellular space. In this form, it can block the inside of the Na+ channel
what type of anaesthesia is an epidural
local
how does epidural anaesthesia work
It reduces pain but still allows the mother to respond to changes in pressure and be able to push
which type of neurone is more sensitive to the effects of local anaethetics
sensory
what are side effects of NSAIDs
GI upset heartburn nausea diarrhoea bleeding
what are the side effects of opioids
- dependency
- constipation
- vomit and nausea
- depression
- respiratory depression
how can opioid side effects be reversed
opioid antagonist such as naloxone
what is a tension headache and where does it affect
associated with physical and mental tension, normally bilateral affecting both sides of the head and often felt at the back of the head
what is a sinus headache and where does it affect
result of inflammation of blocking leading to an increased pressure being felt over the location of the sinuses.
what is a migraine and where does it affect
painful and debilitating form of headache. Migraines are often associated with gastrointestinal upset, and vomiting.
normally unilateral affecting most of the head on one side with a focal point generally located behind the eye
what are cluster headaches and where are they located
rapid onset and strong severity that are associated with changes in the autonomic nervous system. They are called clusters as they may have a number of headaches occurring in close succession.
cluster headaches are associated with
increased excretions, running eyes and nose as a result of the involvement of CNV trigeminal nerve
what are medical overuse headaches
taking too many painkillers may lead to onset of medication overuse headaches
