An investigation by the United States Food and Drug Administration (FDA) into possible misconduct by Upjohn, makers of the sleeping pill Halcion (triazolam), “strongly suggested” that the company knowingly concealed side effects in an early clinical trial, according to an FDA memorandum. Subjects in protocol 321, a study of 28 healthy prisoners for 42 days in 1972, experienced more adverse reactions than were shown in the summary that the pharmaceutical giant submitted to the FDA in its application for approval. The true incidence of side effects emerged only in 1991, when the original data came to light during a court case in the US over Halcion.

The memo of December 1992, obtainable under the US Freedom of Information Act, shows that the FDA considered referring the case to the US Department of Justice for an investigation by a grand jury. But it decided not to go …