Yes. 8 FDA-approved labels for Propylthiouracil carry a boxed warning, and its subject is severe liver injury and acute liver failure, in some cases fatal, have been reported in patients treated with.... A boxed warning is the most serious warning the FDA requires on a prescription label. It is applied to the drug and to the situations in which it is used, not to any particular person taking it.
What the warning says
Below is how the Propylthiouracil warning opens on one specific label, identified underneath it. Of the 8 Propylthiouracil labels sampled, 2 carried materially different wordings and this was the most common, used by 7 of them.
WARNING Severe liver injury and acute liver failure, in some cases fatal, have been reported in patients treated with propylthiouracil. These reports of hepatic reactions include cases requiring liver transplantation in adult and pediatric patients. Propylthiouracil should be reserved for patients who cannot tolerate methimazole and in whom radioactive iodine therapy or surgery are not appropriate treatments for the management of hyperthyroidism. Propylthiouracil may be the treatment of choice when an antithyroid drug is indicated during or just prior to the first trimester of pregnancy (see Warnings and Precautions ).
PROPYLTHIOURACIL, Chartwell RX, LLC, label version effective 26 December 2023. read the full label on DailyMed.Why the wording differs between manufacturers
There is no single official text of a boxed warning. The FDA sets what a warning must cover, and each manufacturer writes its own label within that. Of the 8 Propylthiouracil labels sampled for this page, 2 carried materially different wordings of the same warning, and the version quoted above was used by 7 of them.
The hazard does not change between those 2 versions. Only the sentences do, which is why a refill from a different manufacturer can carry warning text that reads differently without anything about Propylthiouracil or its risks having changed.
Propylthiouracil is dispensed under 8 current FDA labels despite this warning, which is the point worth holding onto: a boxed warning is a disclosure requirement, not a verdict. What a boxed warning does and does not mean sets out the distinction.
Common questions
Does Propylthiouracil have a black box warning?
Yes. 8 FDA-approved labels for Propylthiouracil carry a boxed warning, and its subject is severe liver injury and acute liver failure, in some cases fatal, have been reported in patients treated with.... A boxed warning is the strongest warning the FDA requires on a prescription label, and it is applied to the drug, not to any individual taking it.
What does the Propylthiouracil boxed warning say?
The wording is set by each manufacturer within FDA requirements, so it varies. In the version quoted on this page, taken from a label effective 26 December 2023, the warning concerns severe liver injury and acute liver failure, in some cases fatal, have been reported in patients treated with.... The full text is linked so the exact version can be read rather than summarised.
Does the Propylthiouracil boxed warning mean the drug is unsafe or being withdrawn?
No. It means the FDA requires the risk of severe liver injury and acute liver failure, in some cases fatal, have been reported in patients treated with... to be communicated prominently so prescribers weigh it explicitly. Propylthiouracil remains FDA-approved and is dispensed under 8 current labels. A boxed warning is a disclosure requirement, not a judgement that a drug should not be used.
Why do different pharmacies show different warning text for the same drug?
Because each manufacturer writes its own label within the FDA's requirements. Of 8 Propylthiouracil labels sampled here, 2 carried materially different wordings of the same warning. The hazard described is the same; the sentences are not. This is a common source of confusion when a prescription is refilled with a different manufacturer's product.
Should I stop taking Propylthiouracil because of this warning?
This page does not answer that and cannot. The warning about severe liver injury and acute liver failure, in some cases fatal, have been reported in patients treated with... is written for a prescriber deciding whether Propylthiouracil suits a particular patient, and stopping a prescribed medicine carries its own risks that this page knows nothing about. Raise it with the prescriber or a pharmacist, who can see the whole picture.
Where this page's information comes from
The quotation above is from one Propylthiouracil label, linked below by its DailyMed set identifier so the exact version can be opened rather than taken on trust. The figure of 8 labels, and the count of 2 distinct wordings among 8 sampled, were computed from the openFDA labelling API on 30 August 2026.
- PROPYLTHIOURACIL prescribing information, Chartwell RX, LLC, effective 26 December 2023.
- openFDA drug labelling API, the source of the label counts and variant counts on this page.
Labels are revised over time. The version linked above is the one this page was written against, and a newer revision may differ. Counts reflect the labels present in openFDA on the retrieval date.