Chapter 18: Prostaglandins & Other Eicosanoids

Chapter 18: Prostaglandins & Other Eicosanoids

A 35-year-old woman with moderately severe arthritis has been treated with nonsteroidal anti-inflammatory drugs for 6 mo. Her arthritis symptoms have been well controlled. She now complains of heartburn and indigestion. A fecal blood test is positive. You give her a prescription for a drug to be taken along with the anti-inflammatory agent, but 2 d later she calls the office complaining that your last prescription has caused severe diarrhea and cramping that resembles her periods. Which of the following is most likely to be associated with increased gastrointestinal motility and uterine cramping?

(A) Aspirin

(B) Famotidine

(C) Leukotriene LTB₄

(D) Misoprostol

(E) Zileuton

Aspirin and zileuton rarely cause diarrhea. LTB₄ is a chemotactic factor. Famotidine is an H₂ blocker that does not cause diarrhea (Chapter 16). Misoprostol, a PGE₁ analog, increases gastrointestinal and uterine motility. It is sometimes used as part of an abortifacient. The answer is D.

Which mechanism explains aspirin’s inhibition of thromboxane synthesis?

(A) Blocks cyclooxygenase

(B) Blocks lipoxygenase

(C) Blocks phospholipase A₂

(D) Blocks PGE₁ receptors

(E) Blocks PGI₂ receptors

Hydrocortisone and other corticosteroids inhibit phospholipase. Ibuprofen and indomethacin inhibit cyclooxygenase reversibly, whereas zileuton inhibits lipoxygenase. Because aspirin inhibits cyclooxygenase irreversibly, its action is more effective in platelets, which lack the ability to synthesize new enzyme, than in the endothelium. Aspirin does not block prostaglandin receptors. The answer is A.

A 57-year-old man has severe pulmonary hypertension and right ventricular hypertrophy. Which of the following agents causes vasodilation and may be useful in pulmonary hypertension?

(A) Acetylcholine

(B) Bradykinin

(C) Prostaglandin PGF_2α

(D) Prostacyclin

(E) Thromboxane

Prostacyclin (PGI₂) is a very potent vasodilator. Acetylcholine and bradykinin cause generalized vasodilation and many other undesirable effects; they are not useful in pulmonary or systemic hypertension. PGF_2α and thromboxane are vasoconstrictors. The answer is D.

A 19-year-old woman complains of severe dysmenorrhea. A uterine stimulant derived from membrane lipid in the endometrium is

(A) Angiotensin II