Measurement of plasma glycoside level following pengitoxin administration

16-Acetyl-gitoxin, the cardioactive metabolite of pengitoxin, was estimated by the 86Rb uptake technique. In 70 consecutive patients taking an oral maintenance dose of pengitoxin 0.4 mg (Pentagit), the mean plasma concentration was 20.8 +/- 6.7 ng/ml. Toxic signs were not observed up to plasma levels of 40 ng per ml.