A prominent Canadian medical journal now agrees there’s no clear scientific evidence behind the recommendation to use the drug Diclectin as a “first line” of treatment for nausea and vomiting in pregnant women.

In commentary published this month, the Canadian Family Physician journal says it agrees with the conclusions of a Toronto doctor who has been researching Diclectin and questioning its efficacy for years.

Dr. Nav Persaud, a family physician at St. Michael’s Hospital in Toronto, and a colleague recently published their analysis of a 40-year-old study that helped support the use of Diclectin in Canada and the United States. They found a number of flaws in the study, including incomplete information and data that appeared to be recorded in the patients’ absence.

They concluded that the never-before-published results of the 1970s clinical trial call into question the claimed benefits of Diclectin.

A previous study by Dr. Persaud concluded the drug isn't associated with a reduced risk of birth defects, despite previous research claims.

Diclectin, a combination of pyridoxine (vitamin B6) and doxylamine (antihistamine), is used in half of Canadian pregnancies that result in live births. It is the only prescription drug authorized by Health Canada to treat nausea and vomiting in pregnant women.

Diclectin is recommended by the Society of Obstetricians and Gynaecologists of Canada and the Motherisk program at Toronto’s Hospital for Sick Children. The Canadian Family Physician journal has previously published those recommendations. 

“We agree with the conclusions of Persaud and his colleagues that there is not, at this time, clear evidence that the combination of doxylamine-pyridoxine is more effective in the management of (nausea and vomiting in pregnancy) than pyridoxine alone,” the authors of the commentary wrote.

They also say that recommending Diclectin as a “first line” of treatment “is not supported by the current best evidence.”

The journal suggests that Canadian family physicians could consider pyridoxine alone as a first-line therapy for so-called morning sickness. That recommendation is consistent with clinical practice guidelines in the United States and Australia.

“Family physicians could also consider following the recommendations from the National Institute for Health and Care Excellenceor the Royal College of Obstetricians and Gynaecologists in the United Kingdom, which recommend antihistamines alone,” the journal said.

The CFP commentary also discusses the journal’s dealings with Motherisk, a program that has come under scrutiny over its connection to Duchesnay Inc., the Quebec-based manufacturer of Diclectin.

“Evidence is not static; re-evaluation of accepted truths should not be seen as a weakness as new information comes forward,” the paper says.

When Dr. Persaud’s latest research was published earlier this month, Health Canada responded by saying that its most recent review of Diclectin found “no new safety or efficacy issues.”

The Society of Obstetricians and Gynaecologists of Canada stood by its recommendations and said there is “abundant evidence” that Diclectin is safe.

A spokesperson for Duchesnay also said the safety and efficacy of the drug “have been proven in 16 cohort studies, two meta-analyses, an ecological study, a neurological development study and numerous others.”