When I use a word . . . Paracetamol/acetaminophen—autism and asthma

Among the many examples of serendipity in drug discovery, the antipyretic action of phenacetin was accidentally discovered because of its use by clinicians who were mistakenly supplied with a product that they thought was naphthalene, intended for a different purpose. When phenacetin was later found to be nephrotoxic it was replaced by its active metabolite, paracetamol. Recent news that paracetamol has been reportedly suspected of causing autism in children exposed to it in utero is not news at all. There are studies going back to 2013 that have suggested a possible association. However, the evidence is poor, and even if there is an association one cannot conclude that it is one of cause and effect. Furthermore, various biases may have contributed to the apparent association. The similar case of the supposed association of the use of paracetamol in children with the later development of allergic disorders, attributable to confounding by indication and other biases, taking account, for example, of antibiotic use and viral infections in childhood and recall bias in questionnaire studies, is salutary.