Promethazine (Histantil®)

Last Update: 20 Jun 2025

Medication

Table of content

1. What is it? 2. What are the risks? 3. Breastfeeding/ chestfeeding 4. Fathers and sperm donors 5. Key points

Welcome to our fact sheet on Promethazine (Histantil®) during pregnancy and breastfeeding. This information is based on available published literature. It should not take the place of medical care and advice from your healthcare provider.

The HEALTHY PREGNANCY HUB team is collaborating with MotherToBaby to share information on this topic. The original version is available here (updated on November 2023).

Serene, our chatbot, can also answer your questions about medications during pregnancy.

Please note that this fact sheet is based on United States information and has been adapted for Canada, with a review by our Canadian experts. Minor differences may exist between the two countries. Always consult your healthcare professional for information tailored to your situation.

1. What is promethazine?

Promethazine is a medication that has been is used to treat nausea and vomiting, motion sickness, and allergies. It has also been used for sedation (to help sleep) and for treating vertigo (a feeling of motion or spinning). Promethazine is sold under brand names such as Phenergan®, Promethegan®, and Phenadoz®. In Canada, the brand name is Histansil®.

Sometimes when people find out they are pregnant, they think about changing how they take their medication, or stopping their medication altogether. However, it is important to talk with your healthcare providers before making any changes to how you take your medication. Your healthcare providers can talk with you about the benefits of treating your condition and the risks of untreated illness during pregnancy.

For more information about nausea and vomiting during pregnancy, please see the MotherToBaby fact sheet here.

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2. What are the risks according to research?

I take promethazine. Can it make it harder for me to get pregnant?

Studies have not been done to see if promethazine can make it harder to get pregnant.

Does taking promethazine increase the chance of miscarriage?

Miscarriage is common and can occur in any pregnancy for many reasons. One small study did not report an increased chance of miscarriage in women taking promethazine.

Does taking promethazine increase the chance of birth defects?

Every pregnancy starts out with a 3-5% chance of having a birth defect. This is called the background risk. Use of promethazine during pregnancy is not expected to increase the chance of birth defects above the background risk.

Does taking promethazine in pregnancy increase the chance of other pregnancy-related problems?

It is not known if promethazine can cause other pregnancy-related problems, such as preterm delivery (birth before week 37) or low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth).

Using promethazine late in pregnancy might increase the chance of slowed breathing (respiratory depression) in newborns. It is important that your healthcare providers know you are taking promethazine so that if respiratory depression happens your baby can get the care that is best for them.

Does taking promethazine in pregnancy affect future behavior or learning for the child?

It is not known if promethazine increases the chance for behavior or learning issues.

3. Breastfeeding/ chestfeeding while taking promethazine:

Studies have not been done to see if promethazine can get into breastmilk/chestmilk. Promethazine can cause sleepiness in adults and might have the same effect in a nursing baby. If you suspect the baby has any symptoms (sleepiness or lack of energy), contact the child’s healthcare provider. It is possible that promethazine could reduce how much milk a person makes. If you are having trouble producing milk, talk with your healthcare provider or a lactation specialist. Be sure to talk to your healthcare provider about all your breastfeeding/ chestfeeding questions.

4. Fathers and sperm donors

If a male takes promethazine, could it affect fertility or increase the chance of birth defects?

Studies have not been done to see if promethazine could affect a male’s fertility (ability to get a partner pregnant) or increase the chance of birth defects above the background risk. In general, exposures that fathers and sperm donors have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet on Paternal Exposures here. 

Key points

Promethazine (Histantil®) is used to treat nausea and vomiting, allergies, motion sickness, and sleep disorders.
Available studies do not show an increased risk of birth defects. There are not enough studies to determine whether there are other risks during pregnancy.
In late pregnancy, promethazine may slow the newborn’s breathing. It is important to inform your healthcare team if you are taking this medication.
It is not known whether promethazine passes into breastmilk/ chestmilk.
Always consult your healthcare provider before making any changes to your treatment.

References

Please click here for references.

Disclaimer

HEALTHY PREGNANCY HUB provides a source of information validated by health professionals; however, this information is provided for informational purposes only and should not replace professional advice. Medical standards and practices evolve as new data becomes available, so it is imperative to consult your doctor or a qualified health professional for any questions or concerns regarding your health without delay or omission. It is the responsibility of your treating physician or any other health professional, based on their independent experience and knowledge of the patient, to determine the best way to evaluate and treat you.

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While consulting symptoms or other medical information on our platform may guide your discussions with your healthcare professional, this information should not be used to make a medical diagnosis or determine treatment. Before making changes to your supplement or medication regimen, please discuss with your medical team or contact 811 (Canada) to ensure the relevance of these changes to your individual situation.

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