50 下列那一項藥品不會增加毛地黃中毒的危險？
(A) Cholestyramine
(B) Clarithromycin
(C) Spironolactone
(D) Furosemide

Cholestyramine 會吸附其他藥品造成其他藥品藥效下降

故在服用前1小時或服用後4小時避免和其他藥併用。 

回樓上，我是這樣想

雖然低血鉀會加重digoxin中毒的現象，但digoxin本身機轉應該是造成血鉀上升，再使用個保鉀利尿劑就更容易高血鉀，一樣會有心律不整的風險

而且你上面也寫到Spironolactone may reduce the tubular secretion of digoxin. 

During coadministration, the patient should be monitored for signs and symptoms of digoxin toxicity,

所以我覺得還是選A比較合理
 

有人知道為啥C不能選嗎

低血鉀、低血鎂及高血鈣會加強digoxin的藥效反應，甚至導致中毒現象

我就選了個保鉀..

Interactions between your drugs

Spironolactone may reduce the tubular secretion of digoxin. Plasma clearance of digoxin may be decreased, and plasma levels may increase. Also, limited data indicate that spironolactone may have a negative inotropic side effect. Finally, spironolactone may interfere with some digoxin radioimmunoassays, and digoxin concentrations may be overestimated. During coadministration, the patient should be monitored for signs and symptoms of digoxin toxicity, levels should be checked when necessary, and the clinician should keep in mind the possibility that digoxin levels may falsely appear to be elevated. Patients should be advised to notify their physician if they experience nausea, anorexia, visual changes, or irregular heartbeats.