Nausea Medicine and Morning Sickness: What's Safe During Pregnancy?

Is it safe to take medicine like promethazine while pregnant? Experts weigh in on the pros and cons of treating morning sickness with prescription drugs.

Supplement Vitamins Pills Spread on Wooden Table
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Anyone who's ever dealt with morning sickness will tell you: It's no joke. And now medical experts are shedding a bit more light on the importance of adequately treating pregnancy-induced nausea.

According to Britain's Royal College of Obstetricians and Gynecologists, four out of five pregnant women experience morning sickness through pregnancy and, despite its name, this affliction can strike all day, every day. Because of this, the group has rolled out new guidelines stressing the importance of proper treatment for morning sickness.

"Women with persistent nausea can often feel that there is a lack of understanding of their condition," Dr. Manjeet Shehmar, the lead author of the guidelines, said, according to the BBC. "They may be unable to eat healthily, have to take time off work, and feel a sense of grief or loss for what they perceive to be a normal pregnancy. It is therefore vital that women with this condition are given the right information and support and are made aware of the therapeutic and alternative therapies available to help them cope."

According to the guidelines, there's a lack of understanding about morning sickness. While drug-free therapies like ginger and acupuncture can provide relief, experts believe severe cases of morning sickness may require anti-sickness drugs or even hospital treatment.

Jonathan Schaffir, M.D., an associate professor in the department of Obstetrics and Gynecology at The Ohio State University College of Medicine, says morning sickness ranges from the occasional discomfort to a miserable experience with weight loss, dehydration, and inability to tolerate any food at all. "While the low end of this spectrum may be amenable to non-prescription treatments like bland foods and ginger, the more severe symptoms will usually require some help in the form of medication."

The American Congress of Obstetricians and Gynecologists agrees that treatment depends on the severity of the case. "If diet and lifestyle changes do not help your symptoms, or if you have severe nausea and vomiting [during] pregnancy, medical treatment may be needed," the group said in an emailed statement. "If other medical conditions are ruled out, certain medications can be given to treat nausea and vomiting. You and your obstetrician or other members of your health care team can discuss all of these factors to determine the best treatment for your personal situation."

3 Anti-Nausea Drugs for Morning Sickness

Dr. Schaffir says there are several anti-nausea medications that are used in pregnancy. Here’s some more information about the most common options.

Pyridoxine and Doxylamine

“The most extensively studied medication that has been proven safe is a combination of vitamin B6 (pyridoxine) and doxylamine, which is available over the counter as a sleep aid,” Dr. Schaffir says. Your doctor will give instructions for the medicine, but you’ll likely take it two-three times each day. Possible side effects include drowsiness, dry mouth, headaches, dizziness, gastrointestinal issues, muscle pain, and rash.


Dr. Schaffir says that other antihistamines, such as promethazine, are also safe during pregnancy. The prescription drug promethazine is sometimes used to treat nausea and vomiting (and it’s also prescribed for allergies, motion sickness, and sleep regulation). Common side effects include drowsiness, double vision, nervousness, constipation, and hyperactivity, among others.

Promethazine is classified as a category C pregnancy drug. This means that adverse effects have appeared in animal testing, but there haven’t been enough human studies to confirm any complications during pregnancy. Therefore you should only take promethazine while pregnant when the benefits outweigh the risks. You should also avoid taking the drug within two weeks of delivery since it’s been linked to platelet aggregation in the newborn. Talk to your doctor for more information.


Many women don't like the sedative effects that nausea medications have, because they become too sleepy to work or take care of other children. A non-sedating medicine that is helpful for nausea in pregnancy is ondansetron. Side effects include headache, dizziness, constipation, and fatigue.

“While used widely with no bad effects, the use of ondansetron in the very early part of pregnancy has come under increased scrutiny lately because of conflicting reports that it may be associated with a small increase in the rate of certain birth defects,” says Dr. Schaffir. “This association has by no means been proven, but because of the uncertainty, many caregivers will avoid this medication until after the first two months of pregnancy.” Regardless, he says that if a woman is unable to keep any food or drink down, then the risk of complications of dehydration and insufficient nutrition may be greater than the risk of using this medication.

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