L:\usmle review 7 - Sinoe medical homepage.

(A)
(B)
(C)
(D)
(E)
Allopurinol
Aspirin
Colchicine
Probenecid
Sulfinpyrazone
47. The correct answer is C. The patient has gout, which is due to precipitation of monosodium
urate crystals in joint spaces (notably the great toe) and soft tissues (causing tophi, which are
often found on the external ears). Colchicine reduces the inflammation caused by the urate
crystals by inhibiting leukocyte migration and phagocytosis secondary to an effect on microtubule
assembly.
Allopurinol (choice A) and its metabolite, oxipurinol, inhibit xanthine oxidase, the enzyme that
forms uric acid from hypoxanthine. Therapy with this agent should be begun 1-2 weeks after the
acute attack has subsided.
Aspirin (choice B) competes with uric acid for tubular secretion, thereby decreasing urinary urate
excretion and raising serum uric acid levels. At high doses (more than 2 gm daily) aspirin is a
uricosuric.
Probenecid (choice D) and sulfinpyrazone (choice E) are uricosuric agents, increasing the
urinary excretion of uric acid, hence decreasing serum levels of the substance. Therapy with
these agents should be begun 1-2 weeks after the acute attack has subsided.
48. A Guatemalan child with a history of meconium ileus is brought to a clinic because of a
chronic cough. The mother notes a history of respiratory tract infections and bulky, foul-smelling
stools. After assessment of the respiratory tract illness, the practitioner should also look for signs
of
(A)
cystinuria