NSAIDs & Opioids Flashcards
How are prostaglandins, thromboxanes and leukotrienes produced?
From the eiconsaonid pathway.
Describe the eicosanoid pathway.
When tissues get damaged, inflammation produces phospholipase A2, which converts phospholipids in the membrane into arachidonic acid. COX enzymes (cyclooxygenase) then convert arachidonic acid into eiconsanoids.
What is the rate limiting enzyme in the eiconsanoid pathway?
Phospholipase A2
What is the difference between COX-1 and COX-2?
COX-1 is constantly expressed throughout the body and is responsible for normal gastric function, platelet aggregation and regulation of blood flow.
COX-2 is only expressed at sites of inflammation, mediates the inflammatory response.
What is the MOA of NSAIDs?
Inhibit COX enzymes by competing with arachidonic acid for the active site on COX enzymes - reduces production of prostanoids.
What are the 3 effects of NSAIDs?
Anti-inflammatory
Analgesic
Anti-pyretic
What are the 3 different types of NSAIDs?
- selective COX-1 inhibitors
- selective COX-2 inhibitors
- non-selective COX inhibitors
How are NSAIDs metabolised?
Metabolised hepatically to inactive products (not prodrugs).
Name 3 selective COX-1 inhibitors.
Aspirin
Ibuprofen
Naproxen
Name a non-selective COX inhibitor.
Diclofenac
Name a selective COX-2 inhibitor.
Celecoxib
Which of the eicosanoids does COX-1 produce?
Thromboxane A2 (TXA2)
Which of the eicosanoids does COX-2 produce?
PGI-2
What is the MOA and effects of selective COX-1 inhibitors.
Inhibit COX-1 enzyme, decreasing production of TXA2 - causes vasodilation and reduced platelet aggregation.
What is the function of TXA2?
Platelet aggregation
Vasoconstriction
Name some side effects of COX-1 inhibitors.
- prolonged bleeding due to reduced platelet aggregation
- high risk of GI ADRs e.g. GI bleeding, ulcers
What is the MOA and effects of selective COX-2 inhibitors?
Inhibit COX-2 enzyme, which reduces PGI-2 production, leads to increased vasoconstriction and platelet aggregation.
What are the effects of PGI2?
Vasodilation
Inhibits platelet aggregation
Name some side effects of COX-2 selective inhibitors.
- GI ADRs (but less likely than COX-1 inhibitors)
- renal ADRs
Name some contraindications for NSAIDs.
- decreased renal function - in someone who has decreased renal function, prostaglandins are a significant factor in maintaining blood flow. Use of NSAIDs could increase risk of kidney injury
- cardiovascular disease
- GI disease
What is the effect of NSAIDs on the kidney?
Inhibits prostaglandin-driven afferent arteriole vasodilation, leading to arterial wall thickening, narrowed lumen and reduced blood flow to kidney - risk of kidney injury.
Use of NSAIDs can decrease renin secretion if the kidney is damaged. What ECG changes may this cause?
Decreased renin means reduced aldosterone. Aldosterone causes Na+ reabsorption and K+ secretion, therefore there is less K+ secretion.