Diclegis is a prescription medication used to treat nausea and vomiting during pregnancy, commonly known as morning sickness. It combines two active ingredients, an antihistamine called doxylamine succinate and vitamin B6 (pyridoxine hydrochloride), in a single delayed-release tablet. The FDA approved it in 2013 for pregnant women whose nausea doesn’t improve with dietary and lifestyle changes alone.
What Diclegis Contains
Each Diclegis tablet contains 10 mg of doxylamine succinate and 10 mg of pyridoxine hydrochloride. Doxylamine is an antihistamine, the same type of ingredient found in some over-the-counter sleep aids. Pyridoxine is simply vitamin B6. The tablet has a delayed-release coating, meaning it doesn’t dissolve immediately in the stomach. Instead, it releases the medication gradually, which helps provide longer-lasting relief.
This particular combination of ingredients has a long history. It is essentially a reformulation of Bendectin, a medication originally approved in 1956 and widely prescribed for morning sickness for decades. Bendectin’s manufacturer voluntarily pulled it from the market in 1983 due to litigation costs, not because of safety concerns. The FDA formally confirmed in 1999 that Bendectin’s withdrawal had nothing to do with safety or effectiveness. Diclegis brought the same proven combination back to the U.S. market three decades later.
How It Helps With Morning Sickness
The FDA notes that the exact mechanism behind Diclegis is not fully understood. However, both ingredients are independently known to reduce nausea. Antihistamines like doxylamine block certain chemical signals in the brain that trigger the vomiting reflex. Vitamin B6 has been used on its own as a first-line treatment for pregnancy nausea for years, and combining it with doxylamine appears to produce a stronger effect than either ingredient alone.
In a randomized, placebo-controlled clinical trial involving 261 pregnant women (average gestational age of about 9 weeks), Diclegis produced significantly greater improvement in nausea and vomiting symptoms compared to placebo. Researchers measured this using a standardized scoring system for pregnancy nausea, and the Diclegis group improved by an average of 4.8 points versus 3.9 points in the placebo group. Women taking Diclegis also reported better overall quality of life during the study period.
Who It’s Prescribed For
Diclegis is specifically indicated for pregnant women experiencing nausea and vomiting who haven’t gotten enough relief from conservative approaches. Those approaches typically include eating smaller, more frequent meals, avoiding trigger foods and smells, and staying hydrated. If those strategies aren’t enough, Diclegis is often the next step.
It is not intended for hyperemesis gravidarum, the severe form of pregnancy vomiting that can lead to dehydration and hospitalization, though it may be part of a broader treatment plan in those cases. Most women in the clinical trial were between 7 and 14 weeks pregnant, which aligns with the period when morning sickness tends to be at its worst.
What to Expect: Side Effects
Drowsiness is the most notable side effect. In the clinical trial, about 14% of women taking Diclegis reported feeling sleepy, compared to about 12% on placebo. That relatively small gap reflects the fact that drowsiness is already common in early pregnancy, but the antihistamine component can make it more pronounced. Because of this, you should avoid driving or operating heavy machinery until you know how the medication affects you. Alcohol and other sedating substances can intensify the drowsiness.
The delayed-release design of the tablet is worth noting. You should swallow it whole rather than crushing, chewing, or splitting it, since breaking the coating changes how the medication is absorbed and can increase side effects or reduce effectiveness.
Diclegis vs. Over-the-Counter Options
Since Diclegis contains doxylamine and vitamin B6, both of which are available without a prescription, some women take the two separately as an over-the-counter alternative. This approach is sometimes recommended by healthcare providers as a lower-cost option, especially since brand-name Diclegis can be expensive without insurance coverage.
The key difference is the delayed-release formulation. Over-the-counter doxylamine tablets (sold as sleep aids) release immediately, which means they hit the bloodstream faster and may cause more drowsiness upfront while wearing off sooner. Diclegis is designed to release its ingredients slowly, providing more consistent symptom control throughout the day. Generic versions of the delayed-release combination have also become available, offering a middle ground between the brand-name product and the DIY approach.
Safety Profile in Pregnancy
The doxylamine-pyridoxine combination is one of the most studied medications in pregnancy. Its safety record spans decades, beginning with the original Bendectin formulation in the 1950s. Despite the lawsuits that drove Bendectin off the market, no scientific evidence has ever linked this drug combination to birth defects. Multiple large-scale studies and reviews have confirmed its safety, which is why the FDA approved Diclegis through the same regulatory pathway that referenced the original Bendectin data.
That said, certain women should not take Diclegis. It should not be combined with monoamine oxidase inhibitors, a class of antidepressant that can interact dangerously with antihistamines. Women who are breastfeeding should also use caution, since antihistamines can pass into breast milk and may cause drowsiness or irritability in a nursing infant.