‘To Cause Sleepe Safe and Shure’: Dangerous Substances, Sleep Medicine and Poison Theories in Early Modern England

Recipes found in letters and manuscript receipt books testify to the use of potentially lethal substances in domestic sleep medicine. This article examines the theory behind the use of poisons to induce sleep, contrasting Galenic theory with the radical approach of the Paracelsians. According to Galenic medicine, the coldness of stupefactives such as henbane, deadly nightshade and the opium poppy were useful in counteracting fever and helping a patient to sleep. However, their coldness could also cause death. They were therefore used mainly in external medicine. The exceptions were diacodium made from native poppies that were considered less lethal, and sleeping draughts used in a surgical context. Laudanum, a new drug developed using alchemical methods to separate medicine from poison, broke with traditional safety advice. On account of its novelty, personal experience and recommendation were particularly important in establishing it within the canon of sleeping drugs considered safe for use.