Does the morning sickness drug Diclectin really work?

Research suggests that the morning sickness drug Diclectin is ineffective. So what are pregnant women who suffer from debilitating nausea to do?

Does the morning sickness drug Diclectin really work?

illustration: Stephanie Han Kim and Nicole Duplantis

Krista Thomas sat uncomfortably in a boardroom, shaking and afraid to open her mouth. She wasn’t nervous about sharing her views at the monthly meeting with the vice-presidents of the construction materials firm where she works; rather, she was worried she would throw up on the table. Thomas had been hit with morning sickness, also known as nausea and vomiting of pregnancy (NVP), but she was only a couple of months along and not ready to share her big news. Thankfully, she made it through the meeting and to the washroom, where she dry-heaved in a stall and prayed none of her colleagues could hear her.

Thomas started feeling queasy when she and her husband were on their “conception-moon” in Hawaii—an early sign that their plan to conceive their first child had been successful. Morning sickness typically begins after a woman misses her period, but some, like Thomas, can feel sick in the days following conception. Back home in Calgary, she started vomiting at about seven weeks’ gestation, and her doctor, a mom herself, urged her to try Diclectin—a combination of an antihistamine (doxylamine succinate) and vitamin B6—saying it had worked for her when she was pregnant. Desperate for relief, Thomas decided to give it a try.

Diclectin is the only drug specifically made for NVP that’s approved by Health Canada. Manufactured by Quebec-based Duchesnay, Diclectin has been on the market in Canada for more than four decades, and one prescription is filled for every two live births in the country—that’s nearly 200,000 prescriptions every year. Many women say the pill, which has a pink silhouette of an expectant mom stamped on it, was a lifeline during pregnancy. 

Morning sickness is by far the most common pregnancy complaint, affecting up to 80 percent of expectant mothers. Doctors dole out prescriptions for Diclectin in the hope that it will help women carry on with their lives without constantly throwing up, but the popular pill has recently come under scrutiny for being ineffective. In fact, serious flaws have been revealed in the research that backs the drug, which has some experts wondering how it was even approved in the first place. Is it possible the morning sickness drug that moms swear by doesn’t actually work? And, if that’s the case, what are women facing debilitating nausea to do?


The history of treating morning sickness

The cause of morning sickness is poorly understood, and there are many potential factors. Some contributors may be the slow movement of food due to relaxed stomach muscles during pregnancy, genetic predisposition, psychological factors and hormone changes. Human chorionic gonadotropin (hCG), a hormone produced by the placenta, may also play a role. It peaks at the same time as morning sickness—12 to 14 weeks—and symptoms are worse among women who have elevated levels of the hormone, such as those carrying twins.

No one knows exactly how Diclectin works, either, but antihistamines block brain receptors that control nausea and vomiting, and pregnancy can cause vitamin B6 deficiency, which can lead to adverse reactions to food and chemicals, so a pill that combines the two seems like a good bet to ease morning sickness.

The antihistamine–vitamin B6 combination has been used to treat NVP since the mid-1950s, when a drug called Bendectin came on the market in Canada and the United States. A few years later, thalidomide, a drug with a completely different profile, was approved in Canada to prevent morning sickness, but it was pulled less than a year later, after it was shown to cause serious birth defects. Soon, there were allegations that Bendectin also caused malformations, and in 1983 the manufacturer voluntarily withdrew it from the market due to litigation costs. The claims turned out to be false, but years of scary headlines about the drug left many women with lingering doubts about morning sickness medications.

In 1975, while lawsuits against Bendectin were piling up, Diclectin, a similar formulation, was quietly approved in Canada. When Bendectin was discontinued, Canada became the only country where an antihistamine–vitamin B6 formula was prescribed. The formula wasn’t available in the US again until 2013, but it was propelled back into the mainstream thanks to endorsements from Kim Kardashian, who caught the attention of the Food and Drug Administration when she made efficacy claims on Instagram without mentioning the side effects. “I felt a lot better,” she told her 100-million-plus followers about her experience with the pill, which is called Diclegis in the US.


But not everyone feels better, and those side effects—drowsiness, nervousness, stomach pain, headaches and irritability—can make some women feel worse. “I always felt weird and shaky on Diclectin,” Thomas recalls. “I was foggy at work, and I didn’t like driving.”

Still feeling sick after a few weeks on the medication, Thomas confided in her boss, who was understanding and allowed her to come into the office late, after her worst spell of morning sickness had passed, and work from home if necessary. Meanwhile, Thomas’s doctor increased her dose of Diclectin, but it still didn’t ease her symptoms. “I remember feeling super defeated because I wanted this miracle cure, but I was getting sicker,” she says. “It was brutal.”

The problem with morning sickness

Nausea and vomiting take a toll on women’s physical and mental health, and interfere with their responsibilities and relationships at home and at work. A study published in 2017 in the journal BMC Pregnancy and Childbirth found that more than 60 percent of women with NVP take sick leave, which can have financial implications for those without adequate benefits or insurance. The study also revealed that more than 70 percent of women with morning sickness feel the condition negatively affects their social life and ability to manage their household; 80 percent say it impacts their relationship with their partner. While most women feel better in the second trimester with or without treatment, for up to 20 percent, symptoms persist until the third trimester.

Up to two percent of pregnant women develop hyperemesis gravidarum, a condition of severe nausea and vomiting that leads to nutritional deficiency, dehydration, electrolyte imbalance and weight loss, and threatens the health of the mother and the baby. The Duchess of Cambridge (Kate Middleton) famously suffered from it in all three of her pregnancies. Many women with hyperemesis gravidarum need to be hospitalized to receive intravenous fluids, nutritional support and medication to stop their vomiting.

“There’s a broad range of impact on women’s lives, from very mild, temporary disruption to really significant, debilitating distress,” says Stephanie Rhone, senior medical director of gynaecology and sexual health at BC Women’s Hospital & Health Centre in Vancouver. “But for the vast majority of women, this is a transient and normal part of pregnancy.”


For Thomas, it didn’t feel so normal. Like five percent of women, she was sick right up until—and while—she delivered. In addition to adopting a flexible work schedule, she had to quit spin class, sleep upright to reduce reflux and vomiting, and ask her husband to order takeout, because the smell of cooking made her hurl. She was new to Calgary and wanted to make mom-to-be friends but didn’t have the energy to socialize. Plus, she was worried she’d puke in their presence. “I never left the house, so I got stir-crazy and depressed,” Thomas says. “It’s probably why I would never have a kid again.”

And she’s not alone. The BMC study found that three-quarters of women with severe NVP consider not getting pregnant again. More than a quarter think about terminating the pregnancy.

Like many women, Thomas worried her sickness might be hurting her baby, but her doctor reassured her that as long as she was gaining weight and keeping some food down, her baby would be fine. In fact, several studies show that NVP is actually associated with positive outcomes, including a reduced risk of miscarriage and heart defects.

When morning sickness drugs don’t work

Thomas stayed on Diclectin for a few months, but when her symptoms didn’t improve, she stopped taking the pills. “I thought, I’m still puking—why am I putting this in my body? It didn’t work for me.”

Navindra Persaud, a scientist and staff physician at St. Michael’s Hospital in Toronto, says the medication doesn’t work, period. He started investigating Diclectin in 2011, after a patient asked him a simple question: Should I really take this medicine? He reassured her that the drug is the standard treatment for morning sickness, but she seemed skeptical, so he said he’d look into it further.


When he did, he realized the guidelines from both the Society of Obstetricians and Gynaecologists of Canada (SOGC) and Motherisk (a research and clinical-care program at Toronto’s SickKids Hospital related to drug safety and other exposures during pregnancy) lacked the evidence a medication endorsed as a first-line treatment would normally have. This set Persaud on a seven-year quest to find the answer to his patient’s question.

In a paper published earlier this year in PLOS ONE, Persaud reveals that the 2009 Duchesnay-sponsored clinical study done to gain approval for Diclectin in the US failed to show the drug is effective. To get his hands on a copy of the company’s study report from Health Canada, he had to make an access to information request, sign a confidentiality agreement and promise to destroy it when he was done.

In the trial, 280 women with moderate NVP were given Diclectin or a placebo for two weeks. Their symptoms were assessed using a 13-point scale that measures the frequency of retching, vomiting and nausea. At the end of the trial, the women in the Diclectin group fared slightly better than those in the placebo group, but the difference was less than one point on the scale. The result falls far below the “intended clinical effect” of three points, which Duchesnay set before the trial. Also, more women in the placebo group dropped out than in the Diclectin group, which may have skewed the results.

Persaud says the expected three-point change in symptoms is “the smallest difference that a patient would notice and that clinicians would view as being important enough to consider taking a medication.” Duchesnay spokesperson Fiona Story disagrees with Persaud’s assessment. She says the trial results translate into potentially going from three hours of nausea per day to one or less, from six spells of retching to three, or from four episodes of vomiting to one. “This represents a substantial improvement for the pregnant woman,” she said in an email. “It positively influences her quality of life and allows her to minimize the impact of NVP on her ability to accomplish her professional and personal daily responsibilities.”

In 2016, Health Canada convened a scientific advisory panel to discuss Persaud’s findings before they were published. The panel shared some of Persaud’s concerns about Duchesnay’s trial and said the results are not definitive. “In summary,” the panel wrote, “we would conclude that there is a small statistically significant treatment difference of unclear clinical benefit.” In other words, there’s no proof the drug actually makes women feel better.


In an attempt to understand why Diclectin was approved in the first place, Persaud analyzed other studies related to the drug. He found that an unpublished 1970s clinical trial upon which Health Canada based its approval of the medication had serious methodological flaws, questionable data integrity and a high dropout rate.

One name kept coming up as Persaud pulled back the layers of Diclectin’s approval: Gideon Koren, the founder and former director of Motherisk. Koren authored a number of studies on Diclectin while acting as a paid consultant for Duchesnay, all of them reporting favourable results. The drug company also provided funding for Motherisk, which promoted Diclectin in its pamphlets without declaring the relationship. After the SOGC, which also receives financial support from Duchesnay, released clinical guidelines developed by Motherisk in 2002 lauding Diclectin as the first-line treatment for NVP, prescriptions for the drug shot up 27 percent in one year.

Alternative morning sickness treatments

In a 2014 commentary published in the Journal of Obstetrics and Gynaecology Canada, Persaud reports that there is a lack of evidence that Diclectin works better than vitamin B6 alone, which is available on drugstore shelves and costs a fraction of the price—though for some, Diclectin is covered by insurance. (Before taking B6—or any other supplement, for that matter—it’s important to talk to your doctor about the right dose.) Studies show B6 has only a small treatment effect, but it likely carries fewer risks than Diclectin.

And there may be risks with the medication. While large cohort studies have found no link between Diclectin and birth defects, smaller studies show a slightly increased risk of childhood cancer and pyloric stenosis, a condition in infants that blocks food from the small intestine and causes vomiting. “With these associational studies, you can never say for sure that the relationship is real, but I think anyone taking the medication should be advised of this association,” Persaud says.

In 2017, the College of Family Physicians of Canada published a statement supporting Persaud’s findings and expressing concern about the relationship between Duchesnay and Motherisk. The organization advised physicians to consider vitamin B6 alone as a first-line treatment, which is consistent with clinical practice in Australia and the United States. (In the United Kingdom, antihistamines alone are recommended as an initial treatment.) The SOGC continues to recommend Diclectin as a first-line treatment but gave equal billing to vitamin B6 when it revised its guidelines in 2016.


“Diclectin is considered safe in pregnancy, but as with all medications in pregnancy, we only want to use them when they’re necessary,” says Rhone at BC Women’s Hospital & Health Centre. “If you can manage the symptoms with a less pharmacologic approach, for many women that really is the ideal.”

Rhone recommends starting with diet and lifestyle modifications. Women should eat whatever pregnancy-safe foods appeal to them and avoid those that trigger nausea and vomiting. While some women crave spicy food during pregnancy, others find even the smell revolting. Having an empty stomach, or mixing solids and liquids can exacerbate nausea, and since iron can irritate the stomach, women may want to switch from a multivitamin to just folic acid or a prenatal vitamin without iron until morning sickness passes. Fatigue can intensify symptoms, so getting lots of rest should be a priority.

There is some evidence for alternative therapies. Ginger may ease symptoms. Mindfulness is increasingly being used in medical practice, and a study published in the journal Human Reproduction in 2015 shows it can reduce NVP by helping women manage stress and promoting self-care and relaxation. Acupressure performed on the inside of the arm about three fingers in from the wrist has also been shown to help.

If non-pharmaceutical solutions don’t help, Rhone moves on to medical management, which requires an individualized approach. “From a clinical perspective, some women respond better to certain medications,” she says. “It is always a trial to see how people tolerate medication in terms of side effects and how they respond in terms of managing their symptoms.”

Instead of taking Diclectin, women can talk to their healthcare providers about trying an anti-nausea medication such as Gravol, which is safe to use during pregnancy and available over the counter. There are also drugs that may work and are safe during pregnancy, though their intended use is not to treat morning sickness. For example, metoclopramide is a medication for stomach and esophageal problems that may reduce nausea. Its side effects include headaches and drowsiness. When all else fails, women may be offered Zofran, which treats nausea and vomiting caused by chemotherapy, though there are some safety concerns. Likewise, corticosteroids can be considered for long-term management of severe cases of NVP, although they should be avoided in the first trimester due to an increased risk of cleft lip or palate.


But for some women, nothing works.

This is a harsh reality for those who are suffering. A study published in the British Journal of Obstetrics and Gynaecology found that women with severe NVP have a physical quality of life comparable to those with breast cancer and a mental quality of life similar to those with postpartum depression. So why haven’t we found reliable relief?

Persaud thinks part of the reason is that NVP is a temporary condition that only affects pregnant women. “Women have been failed by medical research and by healthcare providers in Canada,” he says. “We’ve been wasting a lot of time and energy researching and prescribing this ineffective medication and not paying attention to the suffering of women. It’s clear that the medication is not effective, so now we can move on and hopefully identify better approaches to nausea and vomiting in the future.”

In the absence of effective options, many women are self-medicating. Research suggests marijuana use during pregnancy is growing, and more women are using it to treat morning sickness, even though it’s not considered safe during pregnancy. A 2017 commentary in The Journal of the American Medical Association notes that evidence of the effects of cannabis on prenatal development is limited, but some studies have found babies are more likely to have a low birth weight and require intensive care. More research is needed on the potential effects on brain development, the authors conclude.

Persaud is getting more and more questions from pregnant women about using pot to treat NVP, but he cautions them against it, because of the lack of research and potential risks. Similarly, he no longer writes prescriptions for Diclectin. Instead, he tells women that morning sickness is like the common cold: “It causes a lot of suffering, but the reality is, we don’t have an effective treatment for it.” At least, not yet.


This article was originally published on Jul 03, 2018

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