Spironolactone Digitoxin

DIGITOXIN DIURETICS -SPIRONOLACTONE Conflicting results from volunteer studies some showed t (up to one-third) in the half-life of digitoxin, others a 1 (up to one-fifth) Uncertain at present Watch for either digitoxin toxicity or a poor response, particularly for the first month after starting spironolactone... 

Spironolactone has a weak enzjme-inducing effect and enhances the metabolic breakdown of digitoxin (SED-9, 358) (26). However, this effect may not be significant, because in six healthy subjects spironolactone prolonged the half-life of digitoxin from 142 to 192 hours (27). 

Carruthers SG, Dujovne CA. Cholestyramine and spironolactone and their combination in digitoxin elimination. Clin Pharmacol Ther 1980 27(2) 184-7. 

Specificity The cross-reactivity of digitoxin, digitoxigenin, dihydrodigoxin, progesterone, testosterone, ouabain, cholesterol, prednisolone, cortisol, corticosterone, 17-P-estradiol and spironolactone is < 10%. 

A study in 6 healthy subjects who had been taking digitoxin 100 or 150 micrograms daily for 30 days showed that spironolactone 300 mg daily increased the digitoxin half-life by one-third (from 142 to 192 hours). ... 

In contrast, other studies have found that the digitoxin half-life was reduced (from 256 to 205 hours) by spironolactone. ... 

The situation with digitoxin and spironolactone is confusing because the reports are contradictory and the outcome uncertain. Concurrent use should be well monitored. 

Wirth KE, Frolich JC, HolUfield JW, Falkner FC, Sweetman BS, Oates JA. Metabolism of digitoxin in man and its modification by spironolactone. EurJ Clin Pharmacol (1976) 9. 

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