A variable or poor response to a therapeutic agent may not have its origin in the patient; it may be due to a formulation defect in the drug product administered. The most commonly recognized formulation defect in a dosage form such as a tablet is a deficiency or excess of the active ingredient. The fact that difficulties of this type were occurring with certain lots of digoxin and digitoxin tablets on the market was discovered by the Food and Drug Administration through a systematic testing program inaugurated in April, 1970, by the Bureau of Drugs with the testing done at . . .