Why do you think aspirin is contraindicated in people with allergic asthma?

It blocks both COX 1 and 2, therefore, there is more arachidonic acid is available for the production of leukotrienes, hence more leukotrienes are produced, this leads to bronchoconstriction, which is not good for asthma patients.

Arachidonic acid is the most important precursor of the eicosanoids, but how is this fatty acid released from the cell membrane, and by which stimuli?

• Arachidonic acid (AA) must first be released from membrane phospholipids for eicosanoid synthesis to occur.
• There are at least 3 classes of phospholipases contributing to AA release form membrane phospholipids namely:
  • Cytosolic PLA₂ (phospholipase A₂)
  • Secretory PLA₂ (calcium dependent)
  • Calcium independent PLA₂ (chemical and physical stimuli activate Ca²⁺ translocation of PLA₂ to the plasma membrane where it releases arachidonic acid for synthesis of eicosanoids.)

Apart from prostanoids and leukotrienes, which other non-eicosanoid product of cell membrane hydrolysis is strongly involved in asthma?

Why would you say a COX II-inhibitor, and not a COX I-inhibitor, has a selective action in inflammatory reactions?

COX 1: always present in the body, has housekeeping functions such as gastric epithelial cytoprotection.

COX 2: is readily inducible, its levels being dependent on the stimuli. It is common in the kidney, vascular tissue. It’s release is due to stimulus of inflammation, shear-stress, growth factors. Tumour promoters etc.

a drug that inhibits each of the following enzymes: phospholipase A; cyclooxygenase; lipoxygenase,

phospholipase A: hydrocortisone

cyclooxygenase: Aspirin

lipooxygenase: zileuton

a drug that can act antagonistically or agonistically at prostaglandin and leukotriene receptors

Misoprostol

Aspirin inhibits platelet aggregation because it inhibits thromboxane synthesis and not prostacyclin synthesis.  How does it happen?

Irreversibly block cox1 & cox2

How is alprostadil advantageous in the treatment of congenital heart defects?

This is given as infusion to patient to keep heart valve open during surgery.

How is misoprostil of value in the treatment and prevention of gastric ulcers?

This protects the stomach lining, by increasing mucous production and decreasing acid secretion.

Prostaglandin is possible of value in asthma.  Which PG_E2- or PGF_2A-analogues will be effective in such a case?

Epoprostenol

How is latanoprost of value in the treatment of glaucoma?

Increased outflow of aqueous humor.