H2 receptor antagonists
(Date of issue: January 2015. Version: 2)
This factsheet has been written for members of the public by the UK Teratology Information Service (UKTIS). UKTIS is a not-for-profit organisation funded by Public Health England on behalf of UK Health Departments. UKTIS has been providing scientific information to health care providers since 1983 on the effects that medicines, recreational drugs and chemicals may have on the developing baby during pregnancy.
What are H2 receptor antagonists?
H2 receptor antagonists are a group of medicines that includes ranitidine(Gavilast®, Zantac®), cimetidine (Tagamet®), famotidine (PepcidTwo®), and nizatidine. All of these medicines reduce the production of stomach acid and are used to treat indigestion, acid reflux, and ulcers in the digestive system. Ranitidine is also sometimes given before a general anaesthetic to prevent stomach acid from being breathed into the lungs.
Although the H2 receptor antagonists are chemically similar to each other, and it is therefore probable that they will affect a baby in the womb in the same way, we cannot be 100% certain of this. Ranitidine is the H2 receptor antagonist that has been best studied in pregnant women, and has not been shown to harm a developing baby in the womb. Ranitidine is therefore generally preferred over other H2 receptor antagonists for use in pregnancy when lifestyle changes (such as avoiding spicy foods, raising the head of the bed) and antacid or alginate medicines have not helped.
Is it safe to take H2 receptor antagonists in pregnancy?
There is no yes or no answer to this question. When deciding whether or not to take any of these medicines during pregnancy it is important to weigh up how necessary they are to your health against the possible risks to you or your baby, some of which will depend on how many weeks pregnant you are.
This leaflet summarises the scientific studies relating to the effects of ranitidine and other H2 receptor antagonists on a baby in the womb. It is advisable to consider this information if you are taking any of these medicines and are pregnant, or could become pregnant in the future.
Your doctor is the best person to help you decide what is right for you and your baby.
What if I have already taken a H2 receptor antagonist during pregnancy?
If you have taken or are taking any medicines it is always a good idea to let your doctor know that you are pregnant so that you can decide together whether you still need the medicines that you are on and, if so, to make sure that you are taking the lowest dose that works and only for as long as you need to.
Can taking H2 receptor antagonists in pregnancy cause birth defects in the baby?
A baby’s body and most internal organs are formed during the first 12 weeks of pregnancy. It is mainly during this time that some medicines are known to cause birth defects.
A number of studies have investigated groups of women who took any H2 receptor antagonist during pregnancy. All of these studies have shown that the babies of these women are no more likely to have a birth defect than babies of women who did not take H2 receptor antagonists whilst pregnant. However, as discussed above, we cannot be certain that all H2 receptor antagonists will all affect a baby in the womb in the same way. The reassuring results of studies of these medicines as a group therefore do not automatically mean that all H2 receptor antagonists are safe.
Studies have shown no link between taking ranitidine in pregnancy and specific birth defects including cleft lip and/or palate, neural tube defects (e.g. spina bifida), hypospadias (where the hole in the penis is on the underside rather than at the tip), polydactyly (extra fingers or toes), and missing or shortened limbs. A single small study suggested a possible link between taking ranitidine in pregnancy and heart defects in the baby, but heart defects are common (affecting about 1 in every 100 babies born) and any possible link with ranitidine use has not been confirmed. Use of ranitidine in pregnancy is therefore not known to cause birth defects in the baby. No studies have investigated birth defect rates following use of other individual H2 receptor antagonists during pregnancy.
Can taking a H2 receptor antagonist in pregnancy cause miscarriage or stillbirth?
None of three studies of women taking any H2 receptor antagonist during pregnancy have provided any evidence of a link with miscarriage. No studies have investigated this pregnancy outcome for women who took ranitidine or other individual H2 receptor antagonists. .
Two studies of women taking any H2 receptor antagonist during pregnancy provided no evidence of an increased risk of stillbirth. One large study which analysed pregnant women who took ranitidine agreed with this finding. No studies have investigated this pregnancy outcome for women who took other individual H2 receptor antagonists.
Can taking a H2 receptor antagonist in pregnancy cause preterm birth?
Four studies that investigated women taking any H2 receptor antagonist during pregnancy all showed that these women were not at increased risk of having a preterm birth (before 37 weeks). A single study that investigated pregnant women who took ranitidine showed that they may be more likely to have a preterm birth, but could not confirm that this was due to the ranitidine.
Risk of preterm birth has not been studied for the other individual H2 receptor antagonists. More research into whether use of ranitidine (and the other individual H2 receptor antagonists) in pregnancy is linked to preterm birth is therefore required.
Can taking a H2 receptor antagonist in pregnancy cause my baby to be small at birth (low birth weight)?
None of four studies of whether the babies of women who took any H2 receptor antagonist during pregnancy are more likely to be of low birth weight (<2,500g) have provided any evidence of a link. No studies have specifically investigated whether women who take ranitidine or other individual H2 receptor antagonists in pregnancy are at increased risk of having a low birth weight baby.
Can taking a H2 receptor antagonist in pregnancy cause learning and behavioural problems in the child?
A baby’s brain continues to develop right up until the end of pregnancy. It is therefore possible that taking certain medicines at any stage of pregnancy could have a lasting effect on a child’s learning or behaviour.
One study showed that children who had been exposed in the womb to any H2 receptor antagonist met their developmental milestones at the same time as children who had not been exposed in the womb to H2 receptor antagonists. However, we do not know how this relates to children exposed in the womb to each specific H2 receptor antagonist.
There are no known links between taking ranitidine or any of the other individual H2 receptor antagonists in pregnancy and learning and behavioural problems in the child, although no studies have specifically investigated this.
Will my baby need extra monitoring?
As part of their routine antenatal care most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects and to check the baby’s growth. Taking a H2 receptor antagonist in pregnancy would not normally require extra monitoring of your baby.
Are there any risks to my baby if the father has taken a H2 receptor antagonist?
We would not expect any increased risk to your baby if the father took a H2 receptor antagonist before or around the time you became pregnant.
Who can I talk to if I have questions?
If you have any questions regarding the information in this leaflet please discuss them with your health care provider. They can access more detailed medical and scientific information from www.uktis.org.
Up to 1 out of every 5 pregnancies ends in a miscarriage, and 1 in 40 babies are born with a birth defect. These are referred to as the background population risks. They describe the chance of these events happening for any pregnancy before taking factors such as the mother’s health during pregnancy, her lifestyle, medicines she takes and the genetic make up of her and the baby’s father into account.
Medicines use in pregnancy
Most medicines used by the mother will cross the placenta and reach the baby. Sometimes this may have beneficial effects for the baby. There are, however, some medicines that can harm a baby’s normal development. How a medicine affects a baby may depend on the stage of pregnancy when the medicine is taken. If you are on regular medication you should discuss these effects with your doctor/health care team before becoming pregnant.
If a new medicine is suggested for you during pregnancy, please ensure the doctor or health care professional treating you is aware of your pregnancy.
When deciding whether or not to use a medicine in pregnancy you need to weigh up how the medicine might improve your and/or your unborn baby’s health against any possible problems that the drug may cause. Our bumps leaflets are written to provide you with a summary of what is known about use of a specific medicine in pregnancy so that you can decide together with your health care provider what is best for you and your baby.
Every pregnancy is unique. The decision to start, stop, continue or change a prescribed medicine before or during pregnancy should be made in consultation with your health care provider. It is very helpful if you can record all your medication taken in pregnancy in your hand held maternity records.