Influence of wheat bran and of a bulk-forming ispaghula cathartic on the bioavailability of digoxin in geriatric in-patients.

The present randomized study compared the influence of a gel-forming wheat bran with a nongel-forming bulk cathartic (an ispaghula formulation, Vi-Siblin S) on the steady state concentrations of digoxin in plasma in 30 geriatric in-patients treated with either combination (16 with wheat bran + digoxin, 14 with ispaghula + digoxin) for 4 weeks. After 2 but not after 4 weeks, wheat bran reduced the digoxin levels, although the levels were still within the therapeutic range. Ispaghula had no influence at any time. It is concluded that neither wheat bran nor the ispaghula formulation has any clinically relevant influence on therapeutic digoxin levels in geriatric patients.