Differences in Color Vision Impairment Caused by Digoxin, Digitoxin, or Pengitoxin

Color discrimination ability of 53 patients with congestive heart failure and 32 healthy volunteers treated with digoxin, digitoxin, or pengitoxin was determined with the Farnworthʼs Munsell 100 hue test. The patients had been treated with digitalis glycosides for several months prior to color vision testing. The volunteers received glycosides until a steady-state plasma concentration was reached. Glycoside plasma levels were measured by radioimmunoassay on the 3 days prior to color vision testing. The total error scores, indices of color discrimination, increased with the glycoside plasma levels. Subjects treated with digitoxin or pengitoxin exhibited no marked elevation in total error score at therapeutic concentrations, whereas 17 of 28 subjects with therapeutic digoxin plasma concentrations (