MSK: 439 - 441 Flashcards
What pathway produces leukotrienes?
Lipooxygenase
How is arachidonic acid formed?
From membrane lipids (e.g. phosphatidylinositol) via the action of phospholipase A2
What class of drugs inhibits phospholipase A2?
Corticosteroids
What are the 2 pathways that arachidonic acid can take?
- Lipoxygenase
2. Cyclooxygenase
What drug inhibits lipoxygenase?
Zileuton
What is the intermediate between arachidonic acid and leukotrienes?
Hydroperoxides (HPETEs)
What are the four leukotrienes produced in the lipoxygenase pathway?
LTB4, LTC4, LTD4, LTE4
Differentiate LTB4, C4, D4, E4 by their effects.
LTB4 - neutrophil chemotaxis
LTC4, LTD4, LTE4 - bronchoconstriction, vasoconstriction, contraction of smooth muscle, increased vascular permeability
What do zafirlukast and montelukast inhibit?
LTC4, LTD4, LTE4
Remember they are asthma drugs so it makes sense that you would want to inhibit the leukotrienes that are increasing bronchial tone
How many cyclooxygenases are there?
COX-1, COX-2
What are the three things produced in the cyclooxygenase pathway?
- Prostacyclin (PGI2)
- Prostaglandins (PGE2, PGF2)
- Thromboxane (TXA2)
What is the intermediate between arachidonic acid and the ultimate products of the cyclooxygenase pathway?
Endoperoxides (PGG2, PGH2)
Which drugs inhibit cyclooxygenase?
- NSAIDs
- Aspirin
- Acetaminophen
- COX-2 inhibitors
What are the effects of prostacyclin?
Decreased:
- Platelet aggregation
- Vascular tone
- Bronchial tone
- Uterine tone
What are the effects of prostaglandins?
- Increased uterine tone
2. Decreased bronchial tone
What are the effects of thromboxane?
Increased:
- Platelet aggregation
- Vascular tone
- Bronchial tone
Is aspirin a selective or non-selective COX inhibitor?
Non-selective; inhibits both 1 and 2
How does aspirin inhibit COX?
Covalent acetylation
How does aspirin affect bleeding time, PT, and PTT?
Increased bleeding time until new platelets are produced (around 7 days)
No effect on PT, PTT
What category of drug does aspirin fall in?
NSAID
What are the three clinical uses for aspirin and their doses?
Low dose (< 300 mg/day): decrease platelet aggregation
Intermediate dose (300 - 2400 mg/day): antipyretic and analgesic
High dose (2400 - 4000 mg/day): anti-inflammatory
What are the two main side effects of aspirin use?
- Gastric ulceration
2. Tinnitus (CN VIII)
What can chronic use of aspirin lead to (toxicities)?
- Acute renal failure
- Interstitial nephritis
- Upper GI bleeding
When would you worry about Reye syndrome with aspirin?
In children treated with aspirin for viral infection