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Date of issue: January 2023, Version: 1.4

Cyanide is a naturally occurring toxin which may be encountered as hydrogen cyanide (HCN) gas or salts such as potassium cyanide (KCN) and sodium cyanide (NaCN). Cyanide can also be found in plants in the form of cyanogenic glycosides, in drugs such as sodium nitroprusside, and in nitriles (R-CN) which are used widely as solvents and in the manufacture of plastics. The burning of wool, synthetic rubber, polyurethane, and other materials in a house fire may liberate hydrogen cyanide.

Cyanide compounds such as sodium nitroprusside and laetrile have been used therapeutically, however exposure to cyanide in humans is mainly through the ingestion of fruits and vegetables containing cyanogenic glycosides, ingestion of cyanide salts, or inhalation of hydrogen cyanide typically following house fires.

Embryotoxic and teratogenic effects of cyanide have been demonstrated in animal studies, however human data are limited to case reports and are insufficient to provide a full assessment of risk. Owing to the severity of complications associated with cyanide poisoning, treatment of the pregnant patient should be the same as for the non-pregnant patient. If an antidote is indicated for treatment of maternal poisoning this should not be withheld because of pregnancy.

Following acute cyanide exposure in a pregnant patient, maternal toxicity is likely to be a major determinant of fetal risk. However, due to a lack of data concerning the teratogenicity of cyanide, it is not currently possible to state that an absence of maternal toxicity excludes the possibility of adverse events occurring in the developing fetus.

Where exposure to cyanide has occurred, even in the absence of maternal toxicity, enhanced fetal monitoring may be warranted. Discussion with UKTIS is recommended.

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 NHS health care professionals who are logged in.

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 to ensure you are using the most up-to-date version.