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Primary care
Forgotten Primodos story and the roles of general practitioners
  1. Carl Heneghan,
  2. Jeffrey Aronson
  1. Centre for Evidence-Based Medicine, University of Oxford, Oxford, UK
  1. Correspondence to Professor Carl Heneghan, Primary Care Health Sciences, University of Oxford, Oxford OX2 6GG, UK; carl.heneghan{at}

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From 1958 to 1978, over a million women in the UK were subjected to hormone pregnancy tests (HPTs). The principal formulation marketed in the UK, by Schering Chemicals, was called Primodos. Prescribed mainly in general practice or given as free samples by the drug company, Primodos was marketed as a pregnancy test, more convenient than other available tests, such as the commonly used Hogben toad test, which was expensive and took 2 weeks to provide a result.1 Primodos contained oestrogen ethinylestradiol 20 μg and a large dose of the progestogen norethisterone, typically 10 mg, or 40 times the amount in today’s oral contraceptives. It worked by inducing menstrual-like bleeding in non-pregnant women; failure to bleed implied pregnancy.

Because of suspicions of an association with congenital malformations, HPTs created considerable controversy.2 In 1967, the paediatrician Gal, working in a department of obstetrics and gynaecology, published evidence that they caused spina bifida.3 In 1970, the company withdrew pregnancy testing as an indication, but Primodos continued to be prescribed and handed out, because it was still available for treating secondary amenorrhoea. By 1975, a warning about the possible risk of congenital anomalies was added to the label, as was a contraindication in pregnancy. In June 1975, the Committee on Safety of Medicines (CSM) sent an alert to all UK doctors, advising that there might be an association between HPTs and congenital anomalies, and recommending that ‘this method should not now normally be used’. In 1977, the CSM wrote again, saying that the association had been confirmed (see figure 1). This time they wrote that HPTs ‘should not be used’. In 1978, Primodos was removed from the UK market because of concerns about teratogenicity and falling sales. At the time, the Association for Children Damaged …

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  • Twitter @carlheneghan, @JKAronson

  • Contributors CH conceived the article and both authors contributed equally to its drafting.

  • Funding This study was funded by Evidence Synthesis Working Group is part of the National Institute for Health Research School for Primary Care Research (NIHR SPCR) (project number 390).

  • Competing interests CH holds grant funding from the NIHR School of Primary Care Research Evidence Synthesis Working Group (project 390) and the NIHR Oxford BRC. He is editor-in-chief of BMJ Evidence-Based Medicine and an NIHR Senior Investigator. He is Director of the Centre for Evidence-Based Medicine (CEBM), which jointly runs the EvidenceLive Conference with the BMJ and the Overdiagnosis Conference with some international partners, which are based on a non-profit model. JA has written and edited articles and textbooks on adverse drug reactions, including Meyler’s Side Effects of Drugs (16th edition, 2016), its companion volumes the Side Effects of Drugs Annuals, and Stephens’ Detection and Evaluation of Adverse Drug Reactions (6th edition, 2011). He is an associate editor of BMJ Evidence-Based Medicine and a member of the CEBM (see above).

  • Provenance and peer review Not commissioned; externally peer reviewed.