Pain (19.2) Flashcards
What are the functions of pain?
Protects tissue
Detects, localizes, and identifies tissue damaging processes
Gives diagnostic clues (quality, time course, locations)
Define acute pain:
<1 week
Define chronic pain:
At least 6 months (considered an autonomous disease)
What is the chronic regional pain syndrome?
Limb is cold, red, muscle wasting and nail changes
What are opiates?
Derivatives of poppy plants (heroin and morphine)
What are opioids?
Any drug that occupies opioid receptors (fentanyl, methadone)
Which opioid receptor is important for pain?
Mu receptor
Where are Mu receptors found? (generally)
Spread through the CNS and gut and also found on WBCs
How do opioids work in the CNS?
Inhibit GABA and thus disinhibit dopamine
Where in the CNS are Mu receptors found?
Descending pain circuit: amygdala, mesencephalic reticular formation, PAG, rostral ventral medulla
Where in the PNS are Mu receptors found?
Primary afferent neurons, peipheral sensory nerve fibers, DRG
What are the two mechanisms of release for opioids?
Peripherally mediated by stress and ACTH co- release
Centrally mediated involves innervation of the hypothalamus, midbrain and rostral medulla
T/F: Opioids are co released with ACTH during stress reactions from the anterior pituitary
True
What are the releasing mediators for opioids?
5- HETE, LTA4, LTB4 and other lipoxygenase products
Angiotensin II
5- HT
With opioid treatment, what happens to the pressure needed to create pain when opioids are used?
Opioid induced hyperalgesia–> the amount of pressure needed to cause a pain response decreases as the time on opioid increases
What can block the opioid recetor?
Glutamate
Name some criteria that should be followed when prescribing opiods for chronic pain?
Further investigation if the patient has Rx for >1 month
A full physical should be completed
High doses of opiates are generally not helpful
Ongoing risk assessments should be made
What are NSAIDS?
Inhibitors of COX (converts arachidonic acid to prostaglandins and thromboxane)
NSAIDs and Opioids should be used to treat….
Inflammatory pain… NSAIDS decrease inflammation and opioids make patient less concerned about the pain
How do antiepileptic drugs function?
Lowering a neurons ability to fire by hyperpolarization or disallowing depolarization
Why can AEDs be used to treat conditions other than epilepsy?
Treats other conditions like pain/ depression/ anxiety/ migrains because these conditions involve neuronal excessive firing rates
Which pain fibers are involved in neuropathic pain?
C fibers mainly
What are the 3 “bus stops” in inflammatory pain?
Cortical consciousness, Thalamus/ Limbic Subconscious, Spinal reflex
How can inflammatory pain turn into neuropathic pain?
After the inflammation decreases, neurons can get stuck together and cause an excessive/ chronic pain response
Increased Na activity, Increased Ca activity and Increased Glu activity
Name the Na channel blocker AEDs?
Carbamazepine, lamotrigine topiramate
Name the Ca channel blocker AEDs?
Gabapentin and pregabalin
General side effects of AEDs?
Generally may cause sedation psychomotor/ cognitive impairment, ataxia, tremor
Specific side effect of carbamazepine?
aplastic anemia and P450 induction
Specific side effects of lamotrigine?
Stevels Johnson syndrome rash
Specific side effects of gabapentin?
Weight gain and sedation
Specific side effects of pregabalin?
mild addiction, weight gain, sedation
Specific side effects of topiramate?
Weight loss, acidosis glaucoma
How doe antidepressants help treat neuropathic pain?
They work to increase NE in the spinal cord, which in turn decreases pain
Increasing NE causes an increase in ______ which leads to decreased pain.
GABA
What antidepressants are used to treat pain?
SSRI and TCA
