Promethazine is not contraindicated simply because you are pregnant. The Royal College of Obstetricians and Gynaecologists (RCOG) includes it as a first line treatment option for nausea and vomiting in pregnancy, and the UK Teratology Information Service (UKTIS) says that the available data overall do not suggest an association between promethazine exposure during pregnancy and birth defects.
There is an important point behind that reassurance. Promethazine is used off label for pregnancy sickness in the UK. The product information for Phenergan advises that it should only be used during pregnancy when the potential benefits outweigh the potential risks. So, if you are considering it for morning sickness, speak to your GP, midwife or pharmacist rather than starting it yourself.
Key things to know
- RCOG includes promethazine among the first line anti sickness medicines that can be used for nausea and vomiting in pregnancy.
- Current UKTIS data do not suggest that promethazine exposure during pregnancy increases the risk of birth defects.
- Doxylamine with pyridoxine is the only medicine specifically licensed in the UK for pregnancy sickness. Other anti sickness medicines, including promethazine, may be used off label when appropriate.
- High doses of promethazine during late pregnancy can cause neurological effects in a newborn, so use close to delivery needs particular care.
- The UK does not use the old pregnancy letter categories used in some other countries. The FDA retired its letter system in 2015.
- Promethazine can cause significant drowsiness. If you feel sleepy, dizzy or have blurred vision, do not drive or use machinery. Its effects can last for up to 12 hours.
Is promethazine safe in pregnancy
If you have searched for "is promethazine safe in pregnancy", "is promethazine safe during pregnancy" or "can I take promethazine while pregnant", the answer needs a little context.
Current UKTIS information says that the available data overall do not support an association between promethazine exposure during pregnancy and congenital malformations. Limited data also do not suggest increased risks of miscarriage, stillbirth, preterm delivery, low birth weight or adverse neurodevelopmental outcomes.
RCOG also includes promethazine as one of the first line options for treating nausea and vomiting in pregnancy.
Phenergan is a brand of promethazine hydrochloride, so the pregnancy information about promethazine applies to Phenergan too.
That does not mean you should buy Phenergan and start taking it without advice. Pregnancy sickness is an off label use for promethazine, and the product information advises that it should only be used during pregnancy when the potential benefits outweigh the potential risks. Your GP, midwife or pharmacist can help decide whether it is suitable for you.
Promethazine for morning sickness
Searches for "Phenergan for morning sickness", "promethazine for morning sickness", "Phenergan morning sickness" and "promethazine nausea pregnancy" are common. The important thing to know is that there is more than one treatment option.
Nausea and vomiting in pregnancy can affect up to 90% of pregnant women. It commonly starts between weeks four and seven and usually improves by around 20 weeks, although some people continue to have symptoms for longer. Calling it "morning sickness" can also be misleading because nausea and vomiting can happen at any time of day.
UK guidance includes several anti sickness medicines that may be used during pregnancy. Treatment depends on how severe your symptoms are and how well you respond to the medicine.
| Treatment | What it means |
|---|---|
| Self care | Small, frequent meals, avoiding smells or foods that trigger nausea, and drinking fluids regularly may help. |
| First line medicines | Options include promethazine, cyclizine, prochlorperazine, chlorpromazine and doxylamine with pyridoxine. |
| Licensed treatment | Doxylamine with pyridoxine is the only medicine specifically licensed in the UK for nausea and vomiting in pregnancy. |
| Second line medicines | Metoclopramide, domperidone or ondansetron may be considered when earlier treatments have not worked. |
| Hospital treatment | Severe vomiting, dehydration or being unable to keep fluids or medicines down may mean that hospital treatment is needed. |
There is no single timetable that applies to everyone taking an anti sickness medicine. Your treatment may need to be reviewed if your symptoms change, if the medicine is not helping or if side effects are difficult to manage.
If you have severe or persistent vomiting, are losing weight, feel dehydrated or cannot keep fluids down, speak to your GP, midwife or maternity team. You may have hyperemesis gravidarum, which can require medical treatment and sometimes hospital care.
If you had severe pregnancy sickness in an earlier pregnancy, it is also worth discussing this with your healthcare team early in a future pregnancy. They can talk through treatment options before your symptoms become difficult to manage.
Promethazine in pregnancy by trimester
The available evidence is generally reassuring about birth defects, but there are some points to consider at different stages of pregnancy.
First trimester
Questions about "promethazine pregnancy first trimester" are understandable because this is when many people first experience pregnancy sickness and may also be worried about taking medicines.
Current UKTIS data do not suggest that promethazine exposure is associated with congenital malformations. RCOG also includes promethazine among the medicines that can be used for pregnancy sickness.
If you are considering promethazine in the first trimester, speak to your GP, midwife or pharmacist. The right medicine and dose depend on your symptoms, your health and how you respond to treatment.
Second trimester
There is no specific second trimester warning in the current UKTIS information. Many people find that pregnancy sickness improves as pregnancy progresses, although this does not happen for everyone.
If you are still taking an anti sickness medicine, your healthcare professional can review whether you still need it and whether it is working well for you.
Third trimester
Later pregnancy needs a little more care because high doses of promethazine during late pregnancy have been linked with prolonged neurological effects in newborn babies. UKTIS describes possible effects including restlessness, irritability, nightmares and disorientation.
This does not mean that promethazine is automatically prohibited in the third trimester. However, if you are close to your due date, your doctor or maternity team should know that you are taking it so they can consider the timing and dose. UKTIS notes that neonatal monitoring may be considered when exposure occurs close to delivery.
Promethazine pregnancy category C, and why it does not apply here
Searches for "promethazine pregnancy category", "promethazine pregnancy category C", "Phenergan pregnancy category" and "Phenergan pregnancy class" often lead to information from outside the UK.
The old US pregnancy letter system used categories such as A, B, C, D and X. Promethazine was listed as category C under that system. However, the FDA replaced the letter categories in 2015 because a single letter could not explain the full balance of evidence and risk.
The UK does not use this letter system. UK healthcare professionals instead use sources such as the Summary of Product Characteristics, UKTIS and RCOG guidance when considering medicines during pregnancy.
So, if you find "category C" next to promethazine on an overseas website, do not use that letter on its own to decide whether the medicine is right for you. UK guidance and the current product information give more useful information about how promethazine is used during pregnancy.
What promethazine does, and why sedation matters in pregnancy
Promethazine is a first generation antihistamine. It also has anti sickness and sedating effects, which is why it can be used for problems such as nausea, vomiting, allergies and motion sickness.
The sedating effect is one of the most important things to think about during pregnancy. Promethazine can make you sleepy, dizzy or less alert. It can also cause blurred vision. If you are affected, you should not drive or operate machinery. The effects can last for up to 12 hours.
Dry mouth and constipation can also occur. Constipation is already common during pregnancy, so it is worth mentioning if you are considering promethazine.
Some people can experience restlessness or unusual excitement instead of feeling sleepy. If you develop troublesome or unexpected side effects, speak to your GP or pharmacist rather than continuing without advice.
Phenergan in pregnancy, and what the pack is actually for
Phenergan contains promethazine hydrochloride, so the pregnancy information about promethazine also applies to Phenergan.
Phenergan products are used for conditions including allergies and as an anti sickness medicine. Some products are also licensed for short term treatment of insomnia in adults. Pregnancy sickness is not listed as a specific licensed indication for Phenergan, so using it for this purpose is considered off label.
If you are looking for Phenergan for morning sickness, speak to your GP, midwife or pharmacist first. They can consider your symptoms and whether promethazine is appropriate for you.
Promethazine can cause drowsiness, dizziness, dry mouth and constipation. It can also interact with other medicines. For example, Phenergan should be avoided if you are taking or have recently taken a monoamine oxidase inhibitor (MAOI), including within the previous 14 days. It can also increase the sedating effects of other medicines and alcohol.
Long term use should also be discussed with a healthcare professional. The product information says Phenergan should not be used for longer than 7 days without medical advice.
What to ask, and what to tell them
- How many weeks pregnant you are, because the timing of treatment can matter.
- How severe your sickness is and whether you can keep food and fluids down.
- Everything else you take, including medicines bought from a pharmacy, supplements and herbal products.
- Whether you have conditions such as epilepsy, asthma, glaucoma, liver or kidney problems.
- Whether you take or have recently taken an MAOI antidepressant.
- Whether you had severe sickness in a previous pregnancy.
- Whether drowsiness would make it difficult for you to drive, work or care for other children.
Phenergan should not be taken within 14 days of an MAOI. It is also not suitable for children under 6 years of age for the oral products covered by the current Phenergan product information.
When to seek help rather than treat it yourself
Speak to your GP, midwife or maternity team if:
- You cannot keep fluids down.
- You are losing weight or have signs of dehydration, such as passing very little urine or feeling faint.
- Your vomiting is severe or is stopping you from managing normal daily activities.
- You have abdominal pain, fever or other symptoms that do not fit typical pregnancy sickness.
- You are worried about your health or your baby's wellbeing.
If you have concerns about your baby's movements, contact your maternity team promptly rather than trying to manage the problem with an anti sickness medicine.
If you experience a suspected side effect from a medicine during pregnancy or breastfeeding, you can report it through the MHRA Yellow Card Scheme. Reports help regulators collect more information about medicine safety.
Cost, and where the pharmacist fits in
The listed prices for the Phenergan products are:
| Product | Pack | Price |
|---|---|---|
| Phenergan 25mg tablets | 56 tablets | £14.99 |
| Phenergan Elixir 5mg/5ml | 100ml oral solution | £14.49 |
Prices were checked on the product pages at the time of writing, so the live product pages should be treated as the most up to date source.
If you are buying a pharmacy medicine, tell the pharmacist that you are pregnant before purchasing it. This gives them the information they need to check whether the medicine is appropriate for you. For pregnancy sickness, your GP, midwife or another healthcare professional may recommend a different treatment depending on your symptoms.
EveryDayMeds is a UK registered pharmacy, and allergy and sleep medicines are only part of what we supply. If you arrived looking for something else, our weight loss treatments page sets out the options, and there is a fuller guide to Mounjaro treatment.
Mounjaro should not be used during pregnancy. If you are pregnant, planning a pregnancy or breastfeeding, speak to a prescriber about whether it is appropriate for you.
