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Date of issue: October 2022, Version: 4

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A corresponding patient information leaflet on USE OF LEFLUNOMIDE IN PREGNANCY is available.

Leflunomide is currently licensed for the treatment of rheumatoid and psoriatic arthritis. Its use is generally contraindicated during pregnancy due to teratogenicity in several animal models.

The active metabolite of leflunomide is highly protein bound and undergoes extensive enterohepatic recycling, prolonging the half-life of the drug. The manufacturer currently recommends a two-year waiting period after discontinuation of leflunomide before attempting to conceive. If a woman becomes pregnant while taking leflunomide, or within two years of discontinuation, the manufacturer recommends an 11-day washout protocol using colestyramine or activated charcoal to enhance drug elimination.

The available human data comprise a case-control study, a small prospective cohort study, and several case reports/series that collectively describe the outcomes of approximately 500 unique pregnancies exposed to leflunomide. In almost all cases, leflunomide was discontinued upon recognition of pregnancy, usually early in the first trimester. In the majority of exposures, a washout procedure was carried out which potentially limits the level and duration of exposure. Data on miscarriage, low infant birth weight, and preterm delivery following exposure are limited but are currently reassuring.

Leflunomide does not appear to be a major human teratogen if the drug is discontinued and a drug washout procedure is carried out. While malformations have been observed in some exposed pregnancies, there is no obvious pattern suggestive of a specific embryopathy. However, the teratogenicity of leflunomide in humans is undetermined. If in utero exposure to leflunomide has occurred, washout treatment to enhance drug elimination and a detailed structural fetal ultrasound are advised.

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.