USE OF H2 RECEPTOR ANTAGONISTS IN PREGNANCY

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(Date of issue: August 2019, Version: 3)

This is a UKTIS monograph for use by health care professionals. For case-specific advice please contact UKTIS on 0344 892 0909. To report an exposure please download and complete a pregnancy reporting form. Please encourage all women to complete an online reporting form.

A corresponding patient information leaflet on H2 receptor antagonists use in pregnancy is available at www.medicinesinpregnancy.org.

Summary

Histamine H2-receptor antagonists (cimetidine, famotidine, nizatidine and ranitidine) reduce gastric acidity through inhibition of gastric acid production. H2-receptor antagonists are used in the symptomatic relief of episodic dyspepsia and gastro-oesophageal reflux disease, in the prevention and treatment of gastric or duodenal ulceration, and prior to general anaesthesia in patients at risk of acid aspiration. The British National Formulary (BNF) suggests ranitidine as the preferred H2-receptor antagonist for use in pregnancy after lifestyle modification and antacid or alginate treatment have proved unsuccessful in controlling symptoms, or are not considered appropriate.

Data regarding the risk of adverse pregnancy or fetal outcomes following exposure to H2-receptor antagonists as a class are drawn from studies reporting over 4,600 pregnancy exposures collectively. The majority of these studies do not analyse pregnancy outcomes for the individual H2-receptor antagonists separately. There are more data available for ranitidine (over 1,500 pregnancy exposures) and less data available for cimetidine, famotidine and nizatidine.

There is no evidence of an overall increase in the risk of congenital malformation for H2-antagonists. Nor is there good evidence of increased risks of specific malformations. Risks of spontaneous abortion, intrauterine death, low infant birth weight, preterm delivery, neonatal complications or adverse neuro-developmental outcomes do not appear to be increased following exposure to H2-receptor antagonists. However, studies of individual drugs are too small to draw definitive conclusions.

An increased risk of childhood asthma following maternal exposure to H2-receptor antagonists has been reported; however, as data are conflicted and possibly confounded, further research is required.

Exposure to H2-receptor antagonists at any stage of pregnancy would not be regarded as medical grounds for termination of pregnancy or any additional fetal monitoring. However, other risk factors may be present in individual cases which may independently increase the risk of adverse pregnancy outcome. Clinicians are reminded of the importance of consideration of such factors when performing case-specific risk assessments.

This document is regularly reviewed and updated. Only use full UKTIS monographs downloaded directly from TOXBASE.org to be sure you are using the most up-to-date version. The summaries of these monographs are openly available on UKTIS.org

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This is a summary of the full UKTIS monograph for health care professionals and should not be used in isolation. The full UKTIS monograph and access to any hyperlinked related documents is available to health care professionals at www.toxbase.org.

If you have a patient with exposure to a drug or chemical and require assistance in making a patient-specific risk assessment, please telephone UKTIS on 0344 892 0909 to discuss the case with a teratology specialist.

If you would like to report a pregnancy to UKTIS please click here to download our pregnancy reporting form. Please encourage all women to complete an online reporting form.

Disclaimer: Every effort has been made to ensure that this monograph was accurate and up-to-date at the time of writing, however it cannot cover every eventuality and the information providers cannot be held responsible for any adverse outcomes of the measures recommended. The final decision regarding which treatment is used for an individual patient remains the clinical responsibility of the prescriber. This material may be freely reproduced for education and not for profit purposes within the UK National Health Service, however no linking to this website or reproduction by or for commercial organisations is permitted without the express written permission of this service. This document is regularly reviewed and updated. Only use UKTIS monographs downloaded directly from TOXBASE.org or UKTIS.org to ensure you are using the most up-to-date version.