NSAIDs Flashcards
What sorts of pain will NSAIDs be effective for?
pain due to inflammation - only works for mild to moderate pain, but there’s fewer adverse effects
What biochemical pathway is affected by NSAIDs?
the arachidonic acid pathway
Describe the arachidonic acid pathway
trigger activates phospholipase, which releases an arachidonic acid from the membrane phospholipids
arachidonic acid is acted on by loposygenase or cyclooxygenase
lipoxygenase creates leukotrienes
cyclooxygenase makes prostaglandins, thromboxanes and prostacyclins
What enzyme in the arachidonic acid pathway is blocked by NSAIDs?
COX1 and COX2
How are COX1 and COX2 different?
COX1 is active under normal physiology - promotes prostaglandin production that provide gastric cytoprotection, vasodilation, and platelet aggregation
COX2 is inducible in response to inflammation
What effect do thromboxanes have on platelet? How about prostacylincs?
thomboxanes promote platelet aggregation
prostacyclins inhibit platelet aggregation
How are prostaglandins related to pain and why does blocking their production make pain better?
they modify te nociception threshold by making the threshold for activation lower - more sensitive to pain
What is special about aspirin among the NSAIDs?
It irreverisbly inhibits both COX1 and COX2, while the other NSAIDs reversibly inhibit them
What three things are all NSAIDS capable ot?
analgesic
antipyretic
anti-inflammatory
How is the antipyretic effect of NSAIDs mediated?
PGE2 is what triggers the hypothalamus to increase the body temp set point - that’s why you get fever in inflammation
if you use NSAIDs to block PGE2 production, body temp normalizes
What are the adverse effects of the NSAIDS - especially aspirin?
It causes gastrointestinald istress
the prostaglandins that were made by COX1 and had protective effects in the GI system are no longer synthesized, so you get increased gastric acid secretion and decreased mucous secretion, leading to capillary damage, necrosis and bleeding - iron deficiency anemia
increased clotting time
respiratory and electrolyte disturbances
How significant is aspirin’s impact on clotting time?
you get a 2x increase in clotting time for a week after a single dose of aspirin because of the irreversible inhibition of COX (thromboxane synthesis) in platelets
When should you stop NSAIDS before elective surgery? Aspirin specifically
stop NSAIDs 2 days before and aspirin 1 week before
How do the NSAIDs lead to respiratory and electrolyte disturbances?
high doses stimualte respiratory center int he medulla, leading to hyperventilatoin
this hyperventilation causes respiratory alkalosis (increase blood pH)
It can also cause metabolic acidosis because toxic doses of aspirin can uncouple oxidative phosphorylation such that lactic acid accumulates in the serum, decreasing blood pH - this is the bigger deal than above
What are the mild toxicity symptoms with aspirin OD?
tinnitus
headache
nausea, vomiting
sweating, thirst, hyperventilation
hearing loss