02-28-2008, 09:21 AM
21.
Of the following agents, which is best avoided in a patient with a history of chronic congestive heart failure (CHF)?
A.
Hydrochlorothiazide
B.
Amiloride
C.
Mannitol
D.
Ethacrynic acid
E.
Spironolactone
The answer is: C
Mannitol increases serum osmolarity and therefore pulls water out of cells, cerebrospinal fluid (CSF), and aqueous humor. This effect can be useful in the treatment of elevated intraocular or intracranial pressure. However, by expanding the intravascular volume, mannitol can exacerbate CHF.
22.
Of the following agents, which is best avoided when a patient is being treated with an aminoglycoside?
A.
Metolazoneb
B.
Triamterene
C.
Furosemide
D.
Spironolactone
E.
Acetazolamide
The answer is: C
The loop diuretic furosemide is an example of a drug that can cause several drug-drug interactions. Because the loop diuretic can cause hearing impairment, it can augment the ototoxicity that can occur with other drugs, such as aminoglycoside antibiotics (e.g., gentamicin, streptomycin, tobramycin). Furosemide undergoes proximal tubule secretion. This renal secretory mechanism, which is associated with renal excretion, is also available to a number of organic acids, such as the salicylates. When salicylates are present in the body, furosemide is a competitive inhibitor of their excretion by this particular mechanism in the proximal tubule; therefore, the plasma levels of salicylates are increased with the potential for adverse reactions in the patient. Furosemide can enhance the toxicity of lithium by reducing its renal excretion.
23.
Hyperkalemia is a contraindication to the use of which of the following drugs?
A.
Acetazolamide
B.
Chlorothiazide
C.
Ethacrynic acid
D.
Chlorthalidone
E.
Spironolactone
The answer is: E
Spironolactone is a competitive antagonist of aldosterone that blocks the reabsorption of Na and water from the collecting duct in exchange for K and hydrogen ion retention. Therefore, in the presence of hyperkalemia, spironolactone is contraindicated. The administration of each of the other diuretic agents listed results in increased excretion of K.
24.
Acute uric acid nephropathy, which is characterized by the acute overproduction of uric acid and by extreme hyperuricemia, can best be prevented with which of the following?
A.
Antidiuretic hormone (ADH) [vasopressin (VP)]
B.
Cyclophosphamide
C.
Allopurinol
D.
Amiloride
E.
Sodium chloride (NaCl)
The answer is: C
Acute hyperuricemia, which often occurs in patients who are treated with cytotoxic drugs for neoplasic disorders, can lead to the deposition of urate crystals in the kidneys and their collecting ducts. This can produce partial or complete obstruction of the collecting ducts, renal pelvis, or ureter. Allopurinol and its primary metabolite, alloxanthine, are inhibitors of xanthine oxidase, an enzyme that catalyzes the oxidation of hypoxanthine and xanthine to uric acid. The use of allopurinol in patients at risk can markedly reduce the likelihood that they will develop acute uric acid nephropathy.
25.
Spironolactone can be characterized by which one of the following statements?
A.
It is biotransformed to an inactive product
B.
It binds to a cytoplasmic receptor
C.
It is a more potent diuretic than is hydrochlorothiazide
D.
It interferes with aldosterone synthesis
E.
It inhibits Na reabsorption in the proximal renal tubule of the nephron
Of the following agents, which is best avoided in a patient with a history of chronic congestive heart failure (CHF)?
A.
Hydrochlorothiazide
B.
Amiloride
C.
Mannitol
D.
Ethacrynic acid
E.
Spironolactone
The answer is: C
Mannitol increases serum osmolarity and therefore pulls water out of cells, cerebrospinal fluid (CSF), and aqueous humor. This effect can be useful in the treatment of elevated intraocular or intracranial pressure. However, by expanding the intravascular volume, mannitol can exacerbate CHF.
22.
Of the following agents, which is best avoided when a patient is being treated with an aminoglycoside?
A.
Metolazoneb
B.
Triamterene
C.
Furosemide
D.
Spironolactone
E.
Acetazolamide
The answer is: C
The loop diuretic furosemide is an example of a drug that can cause several drug-drug interactions. Because the loop diuretic can cause hearing impairment, it can augment the ototoxicity that can occur with other drugs, such as aminoglycoside antibiotics (e.g., gentamicin, streptomycin, tobramycin). Furosemide undergoes proximal tubule secretion. This renal secretory mechanism, which is associated with renal excretion, is also available to a number of organic acids, such as the salicylates. When salicylates are present in the body, furosemide is a competitive inhibitor of their excretion by this particular mechanism in the proximal tubule; therefore, the plasma levels of salicylates are increased with the potential for adverse reactions in the patient. Furosemide can enhance the toxicity of lithium by reducing its renal excretion.
23.
Hyperkalemia is a contraindication to the use of which of the following drugs?
A.
Acetazolamide
B.
Chlorothiazide
C.
Ethacrynic acid
D.
Chlorthalidone
E.
Spironolactone
The answer is: E
Spironolactone is a competitive antagonist of aldosterone that blocks the reabsorption of Na and water from the collecting duct in exchange for K and hydrogen ion retention. Therefore, in the presence of hyperkalemia, spironolactone is contraindicated. The administration of each of the other diuretic agents listed results in increased excretion of K.
24.
Acute uric acid nephropathy, which is characterized by the acute overproduction of uric acid and by extreme hyperuricemia, can best be prevented with which of the following?
A.
Antidiuretic hormone (ADH) [vasopressin (VP)]
B.
Cyclophosphamide
C.
Allopurinol
D.
Amiloride
E.
Sodium chloride (NaCl)
The answer is: C
Acute hyperuricemia, which often occurs in patients who are treated with cytotoxic drugs for neoplasic disorders, can lead to the deposition of urate crystals in the kidneys and their collecting ducts. This can produce partial or complete obstruction of the collecting ducts, renal pelvis, or ureter. Allopurinol and its primary metabolite, alloxanthine, are inhibitors of xanthine oxidase, an enzyme that catalyzes the oxidation of hypoxanthine and xanthine to uric acid. The use of allopurinol in patients at risk can markedly reduce the likelihood that they will develop acute uric acid nephropathy.
25.
Spironolactone can be characterized by which one of the following statements?
A.
It is biotransformed to an inactive product
B.
It binds to a cytoplasmic receptor
C.
It is a more potent diuretic than is hydrochlorothiazide
D.
It interferes with aldosterone synthesis
E.
It inhibits Na reabsorption in the proximal renal tubule of the nephron