In some countries, doxylamine-pyridoxine is recommended to treat nausea and vomiting during pregnancy. One published randomised controlled trial of this combination product was relied on as evidence of efficacy by the US Food and Drug Administration, which approved it in 2013.
In PLoS One (17 January 2018), researchers analysed unpublished individual-level data from the trial, including 131 people who received 2–14 doses of doxylamine-pyridoxine 10mg for 14 days, and 125 people assigned to placebo
. At the end of the trial, there were missing data on 30 and 39 of these participants, respectively.
The researchers found that, at less than one point, the magnitude of difference in symptom scores did not reach the pre-specified minimal clinically important difference of 3 points on a scale of 13. While there was a statistically significant improvement in symptom scores with active treatment compared with placebo, this was only true when the missing data were handled in a particular way.
The team concluded that the findings called into question the efficacy of the drug and highlighted the importance of making individual-level data from clinical trials available.
This article was amended on 9 March 2018 to clarify that researchers re-analysed data from a published randomised controlled trial that led to the approval of the combination product by the US Food and Drug Administration, not the only trial, as previously stated.
 Persaud N, Meaney C, El-Emam K et al. Doxylamine-pyridoxine for nausea and vomiting of pregnancy randomised placebo controlled trial: Prespecified analyses and reanalysis. PloS One 2018; 13: e0189978. doi:10.1371/journal.Pone.0189978