Phenformin (DBI) — the “Imminent Hazard” Diabetes Pill Banned in 1977, Half Its Victims Dead

When Joseph Califano, Secretary of Health, Education and Welfare, signed the order suspending phenformin on 25 July 1977, he was invoking a power Congress had granted the Food and Drug Administration fifteen years earlier and which no official had ever used: the declaration that an approved medicine was an “imminent hazard to the public health.” Phenformin (phenethylbiguanide), synthesized in 1957 by a team including Seymour Shapiro at the U.S. Vitamin Corporation and marketed in the United States from 1959 by Ciba-Geigy as DBI, had been prescribed to control adult-onset diabetes for nearly two decades. It was withdrawn not because it failed to lower blood sugar — it did that adequately — but because it could quietly poison the body with lactic acid, a complication that killed roughly one of every two patients it reached.

The gap between the promise and the harm was the gap between a surrogate benefit and a survival outcome. Phenformin reliably reduced glycemia, the number physicians could see on a chart; what it did not reliably do was keep patients alive. The biguanide’s mechanism — pushing cellular metabolism toward anaerobic glycolysis — produced excess lactate, and in patients with even modest kidney or heart impairment that lactate could accumulate into a metabolic catastrophe. Phenformin-associated lactic acidosis ran at roughly 40 to 64 cases per 100,000 patient-years, and once it occurred it was fatal in approximately half of cases. The drug treated a chronic disease by trading a visible, manageable problem for an occasional, lethal one.

The verdict was therefore plain long before the suspension. As early as 1959 — the same year U.S. marketing began — the literature linked biguanides to lactic acidosis. In 1971 the federally funded University Group Diabetes Program (UGDP) terminated its phenformin arm after finding excess total and cardiovascular mortality, roughly double that of the placebo and insulin groups combined. By October 1976 the FDA’s own Endocrinology and Metabolism Advisory Committee had recommended removal. The harm sat in the published record for years while ~385,000 Americans were still taking the drug in 1977.

What forced the cord was not the agency but a consumer group and a lawyer’s petition. Ralph Nader’s Health Research Group petitioned for suspension on 22 April 1977; Califano acted in July; the drug was off the U.S. market by 15 November 1978. The episode became the founding precedent for emergency drug suspension, the cautionary prologue to its safer sister biguanide metformin, and the textbook case of how a medicine can be effective on the metric it was sold on and still be a net killer.