Which of the following explains the GI complaints associated with aspirin use?
– decreased production of PGs that promote mucus secretion
COX-1 is in stomach
Choose the reason why aspirin increases bleeding time:
–TXA2 production in platelet decreases
Prevents platelet aggregation
The use of aspirin in pregnancy is contraindicated:
Yes
PGs effect uterus
What is caused and what group of drugs are used to treat this property?
number of chemical mediators released at sites of inflammation release arachidonic acid which is metabolized to prostaglandins– prostaglandins directly cause vasodilation which can lead to edema formation
Anti-inflammatory
NSAIDs
What is caused and what group of drugs are used to treat this property?
chemical mediators, such as interleukin-1, can induce the synthesis of prostaglandins (PGE2) which act within hypothalamus to elevate body temperature
Anti-pyretic
NSAIDs
What is caused and what group of drugs are used to treat this property?
prostaglandins lower pain threshold by increasing sensitivity of pain receptors to chemical mediators, such as bradykinin and histamine
Analgesic
NSAIDs
What is the mechanism of action of all NSAIDs?
Inhibition of cyclooxygenase
COX-1 = constitutive COX-2 = inducible
What is special about the NSAIDs acetylsalicyclic acid (Aspirin)?
It is the only irreversible inhibitor of both COX-1 and COX-2
– acetylation of serine group of COXs
What drug is the only irreversible inhibitor of both COX-1 and COX-2?
Acetylsalicylic acid; Aspirin
What are the therapeutic implications of acetylsalicylic acid (Aspirin) on platelets vs endothelial cells?
Irreversible inhibition
Platelets: No nucleus, so no protein synthesis
Endothelial cells: nucleus, protein synthesis
What affects the absorption of aspirin?
How is aspirin distributed?
- crosses BBB and placental barrier
How is acetylsalicylic acid (Aspirin) metabolized?
Aspirin hydrolyzed (deacetylated) by Phase I (CYP) in blood=> Salicylic Acid
Salicylic Acid => Less polar metabolites
What does chewing aspirin do?
Increases rate of absorption
Who has a longer half-life: aspirin of salicylic acid?
Aspirin: 15 min
Salicylic acid: 2-3 hours
In overdose situations of Aspirin, half-life of salicylic acid becomes dependent on?
Dose/Zero order kinetics
What are unique effects of Aspirin/salicylates that are not related to inhibition of COX?
At low doses of aspirin, what is the effect on uric acid excretion?
Decreased uric acid excretion:
at low doses, aspirin competes with uric acid for secretion by organic acid transport (OAT) system into renal tubules
At high doses of aspirin, what is the effect on uric acid excretion?
Increased uric acid excretion:
at high doses, aspirin competes with uric acid for both secretion and reabsorption and decreases serum uric acid
Block reabsorption via interaction with OAT
What is the role of PGs in uricosuric effects?
PGs have no effect on uric acid excretion
What is the effect of aspirin on the CNS at high doses?
Toxicity related effects
aspirin crosses the BBB:
What are the GI AEs with NSAIDs?
gastric irritation which can lead to gastric ulcers and bleeding
mechanism: inhibition of COX-1 in GI prevents production of cytoprotective prostaglandins
What are the blood AEs with NSAIDs?
increased bleeding time
mechanism: inhibition of COX-1 in platelet blocks production of platelet thromboxane and decreases platelet aggregation
How can NSAIDs cause hypersensitivity?
mechanism: may be due to action of leukotrienes because of shunting of AA pathway from COX to lipoxygenase
Tx: epinephrine