By Dennis Thompson
WEDNESDAY, Jan. 17, 2018 (HealthDay News) -- The most commonly prescribed medicine for morning sickness may not work, a new report contends.
The drug, Diclegis, failed to meet minimum effectiveness goals in the clinical trial relied upon by the U.S. Food and Drug Administration for its approval in 2013, Canadian researchers reported.
"There was a very small difference between the women who got a placebo and the women who got this medicine," said Dr. Nav Persaud, a researcher and family physician at St. Michael's Hospital in Toronto.
Given that, the FDA should reconsider its approval of Diclegis, Persaud said.
"I think medications should only be approved and prescribed if they're proved to be effective," Persaud said. "The very basic question that needs to be answered is if it's effective. If the medication is not effective, it doesn't matter if it's safe or not."
But one of the nation's leading medical associations, the American College of Obstetricians and Gynecologists (ACOG), responded to the new paper with the equivalent of a yawn.
Just this month, ACOG updated its practice guidelines for treating nausea and vomiting during pregnancy, maintaining that Diclegis "is safe and effective and should be considered first-line pharmacotherapy," said Dr. Mark Turrentine, chair of ACOG's Practice Bulletin Obstetrics Committee.
"If the U.S. Food and Drug Administration, the authors of the original studies, or the drug manufacturer correct or retract any of the evidence used to develop ACOG's guidance, we will reassess and consider the conclusions at that time," Turrentine said in a statement.
Diclegis is the combination of an antihistamine, doxylamine succinate, with a form of vitamin B6 called pyridoxine hydrochloride.
This combination drug had been available for in the United States starting in the 1950s, but was voluntarily pulled from the market in the 1980s over concerns that it was linked with birth defects.
But lawsuits related to those claims were eventually dismissed, and efforts began in the 2000s to get the drug back onto the U.S. market, Persaud said. The drug has always been available in Canada and is currently sold there as Diclectin.
Persaud and his colleagues reviewed the 9,000-page clinical study report submitted by the drug's manufacturer, Duchesnay Inc., based in Quebec, Canada. Results of the short two-week trial, which involved 187 women at six U.S. medical centers, were published in 2010.
The clinical trial had set a goal of improving symptoms by 3 points on a 13-point scale, but the researchers found that Diclegis had only resulted in a 0.73-point improvement.
While the results were statistically significant, they were not large enough to be noticeable by women taking the medication, the Canadian researchers argue. Most women given a placebo had few or no symptoms by the end of the two-week trial.
There's no evidence that Diclegis produces birth defects on the scale of a drug like thalidomide, Persaud said, but some concerns do remain about its safety.
"No medication is ever going to be perfectly safe," Persaud said. "If this medication was proven to be effective, you could look at those small potential risks and say overall if it's going to make women feel better it's probably worth it, but if the medication is not proven to be effective then it's not clear what would balance off those risks."
Duchesnay responded to the new paper with a statement noting that the safety and effectiveness of Diclegis has been proven in at least 20 different studies and evidence reviews, and that ACOG, the Society of Obstetricians and Gynecologists of Canada, and the Association of Professors of Gynecology and Obstetrics all recommend the drug as first-line therapy for morning sickness.
"It has been thoroughly studied for both safety and efficacy, but equally as important, it has been successfully used for decades by pregnant women to manage [morning sickness]," the company said.
Given how well the drug has worked in practice, the new paper is "much to do about nothing," said Dr. Fahimeh Sasan, an assistant professor of obstetrics, gynecology and reproductive science at the Icahn School of Medicine at Mount Sinai, in New York City.
No one would argue that it was a very small study, and that the improvement in symptoms didn't reach the benchmark initially set, Sasan said.
But in everyday life the drug has proven very effective, said Sasan, who works at a "very bustling, busy" obstetrics practice on the Upper East Side of Manhattan that performs 750 to 800 deliveries a year.
"Anecdotally, from our practice, we do see a significant benefit," Sasan said. "It actually has been quite effective and our patients are very pleased while they take it."
In addition, nothing in this study raises any red flags regarding the overall safety of Diclegis, Sasan said.
"It's safe, and within our practice we are finding that women only have to take it once a day," Sasan said, adding that other nausea/vomiting drugs require multiple daily doses and come with more significant side effects.
The study was published online Jan. 17 in the journal PLOS ONE.