Drugs › Thyroid hormone synthesis inhibitor
Generic name
Propylthiouracil: adverse event reports filed with FDA
1,218 reports list it as a suspect or interacting product, 2004–2026. Class: Thyroid hormone synthesis inhibitor. Also reported as Propylthiouracil Tab, Propylthiouracil Tablets Usp.
- 1,218
- reports as suspect product
- 0% of all reports · about 54 a year
- 111
- reports, 12 months to June 2026
- 161 in the 12 months before
- 93.6%
- marked serious by the reporter
- 87.2% across the class
- 7.9%
- record death among outcomes, as reported
- 96 reports · not verified by FDA
Between January 2004 and June 2026, 1,218 adverse event reports received by FDA list propylthiouracil, a generic name as a suspect or interacting product. Reports that mention it only as a concomitant medication (929) are left out of every figure here.
In the 12 months to June 2026, 111 reports listed it, down 31% from 161 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Over its reporting history that is about 54 reports a year and 0% of the 20,646,523 reports in the database, and 32.6% of the reports for the thyroid hormone synthesis inhibitor class. How many people take it is not in the data, so a count is not a rate of occurrence.
The MedDRA terms listed most often are drug ineffective (11.1%), foetal exposure during pregnancy (9.3%) and anti-neutrophil cytoplasmic antibody positive vasculitis (7.1%). A report can list several reactions, so shares add to more than 100%; 371 different terms appear across these reports. Drug ineffective is recorded in 11.1% of these reports, about the same share as in the median thyroid hormone synthesis inhibitor drug (11.7%).
93.6% of the reports are marked serious by the reporter (87.2% across the class); 7.9% record death among the outcomes and 48.9% record hospitalisation, as reported. 53% of the reports came from other health professionals, and the largest patient age group is 18 to 44 (34.8%). FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event."
Reports by month, five years
Reports by the month FDA received them. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.
By year received
2026 covers reports received through June 2026 only.
Reactions recorded in the reports
share of Propylthiouracil reports recording the termmedian drug in thyroid hormone synthesis inhibitor
- Drug ineffectivethe medicine did not work as expected11.1%135
- Foetal exposure during pregnancythe unborn baby was exposed to the medicine9.3%113
- Anti-neutrophil cytoplasmic antibody positive vasculitis7.1%87
- Exposure during pregnancythe medicine was taken during pregnancy6.1%74
- Hyperthyroidismoveractive thyroid5.8%71
- Agranulocytosis5.2%63
- Maternal exposure during pregnancythe mother took the medicine during pregnancy4.9%60
- Off label useused for a purpose or in a way not on the label4.4%54
- Acute hepatic failure3.2%39
- Vasculitisinflammation of blood vessels3.1%38
- Premature babya baby born early3%37
- Neutropenialow neutrophils, a type of white blood cell3%36
- Pyrexiafever2.9%35
- Anaemialow red blood cells2.4%29
- Hepatotoxicityliver injury2.4%29
- Condition aggravatedthe condition being treated got worse2.1%25
- Drug reaction with eosinophilia and systemic symptomsDRESS, a severe reaction with rash, fever and organ involvement2.1%25
- Thyrotoxic crisis2.1%25
- Multiple organ dysfunction syndromeseveral organs failing1.7%21
- Sepsisa severe body-wide response to infection1.7%21
- Acute kidney injurysudden loss of kidney function1.6%20
- Nauseafeeling sick1.6%20
- Premature delivery1.6%20
- Rhabdomyolysismuscle breakdown1.6%20
- Antineutrophil cytoplasmic antibody positive1.6%19
- Product use in unapproved indicationused for a purpose not on the label1.6%19
- Cardiogenic shockshock from the heart failing to pump1.5%18
- Hypotensionlow blood pressure1.5%18
- Hypothyroidismunderactive thyroid1.5%18
Top 30 of 371 MedDRA preferred terms recorded across these reports, with a plain-language gloss where one is available. One report can record several terms. The hollow bar is the median share across the 2 drugs in the thyroid hormone synthesis inhibitor class; it describes the reports, not the patients. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."
Outcomes recorded
Outcome flags as the reporter set them; a report can carry several, and "other serious" is FDA's own category for serious reports outside the named outcomes. Grey bar: all 3,734 reports in the class. FDA has not verified any outcome and states that the reports "cannot be used to estimate the incidence of these events."
Patients and reporters
Patient age
Patient sex
Who reported
Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 40.3% of reports give the United States as the country of the event or reporter.
Reason for use recorded
| Indication as recorded (MedDRA) | Reports | Share |
|---|---|---|
| Hyperthyroidism | 432 | 35.5% |
| Graves' disease | 129 | 10.6% |
| Basedow's disease | 115 | 9.4% |
| Thyrotoxic crisis | 114 | 9.4% |
| Basedow's disease | 53 | 4.4% |
| Toxic nodular goitre | 7 | 0.6% |
The indication field is filled in by the reporter and is often blank; shares are of all 1,218 reports.
Drugs most often listed in the same reports
| Drug (any role in the report) | Reports | Share of Propylthiouracil reports |
|---|---|---|
| Propranolol | 226 | 18.6% |
| Methimazole | 209 | 17.2% |
| Hydrocortisone | 133 | 10.9% |
| Furosemide | 72 | 5.9% |
| Cholestyramine | 71 | 5.8% |
| Metoprolol | 70 | 5.7% |
| Amiodarone | 58 | 4.8% |
| Prednisone | 44 | 3.6% |
| Aspirin | 42 | 3.4% |
| Bisoprolol | 42 | 3.4% |
Other products listed in reports where Propylthiouracil is a suspect product, whatever their own role. Co-listing means the two were recorded together; it says nothing about either product's part in the event. Only the 2,500 most-reported names are counted here.
In context
| Measure | Propylthiouracil | Thyroid hormone synthesis inhibitor | All reports |
|---|---|---|---|
| Reports as suspect product | 1,218 | 3,734 | 20,646,523 |
| Share of that pool | — | 32.6% | 0% |
| Reports, latest 12 months | 111 | — | 1,332,454 |
| Marked serious | 93.6% | 87.2% | 57.4% |
| Death recorded among outcomes, per 1,000 reports | 79 | 77 | 91 |
| Hospitalisation recorded, per 1,000 reports | 489 | 451 | 213 |
| Consumer-filed share | 5.5% | 12.1% | 45.8% |
| Top term, share of reports | Drug ineffective 11.1% | median 11.7% | 6.3% |
Shares are of reports, not of patients treated. The number of people taking a product is not in the data, so none of these figures is a rate, and differences between columns reflect who takes a product, who reports and how long it has been sold. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."
Other drugs in the thyroid hormone synthesis inhibitor class
| Drug | Name type | Reports | Latest 12 months | Marked serious |
|---|---|---|---|---|
| Methimazole | generic | 2,516 | 240 | 84.1% |
Ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic." A brand and its generic are separate rows because reporters name them separately.
Questions about Propylthiouracil reports
How many adverse event reports has FDA received for Propylthiouracil?
1,218 reports list Propylthiouracil as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 111 of them arrived in the latest 12 months. Another 929 list it only as a concomitant medication.
What reactions are recorded in Propylthiouracil reports?
drug ineffective (11.1%), foetal exposure during pregnancy (9.3%), anti-neutrophil cytoplasmic antibody positive vasculitis (7.1%), exposure during pregnancy (6.1%) and hyperthyroidism (5.8%). These are MedDRA preferred terms coded from what the reporter described; a report can list several, and a term's presence is not a finding that Propylthiouracil was responsible.
How serious are the reports?
93.6% are marked serious by the reporter. Among the outcomes recorded, 7.9% of reports include death and 48.9% include hospitalisation. FDA has not verified these outcomes and states that the reports "cannot be used to estimate the incidence" of the events.
Who files these reports?
other health professional (53%), physician (30.9%) and not given (5.6%). Most reports reach FDA through the manufacturer, which must forward reports it receives.
Are reports for Propylthiouracil rising?
111 reports in the 12 months to June 2026, down 31% from 161 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Counts also move with how many people take a product, its time on the market and publicity.
Do these reports show that Propylthiouracil was responsible for these reactions?
No. FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event." The reaction may relate to the condition being treated, to other medicines, or to something else.
Is this a list of the side effects of Propylthiouracil?
No. It is a count of what was reported to FDA. The adverse reactions observed in clinical studies are printed on the FDA-approved label, which a pharmacist or clinician can go through with you.
How do I report an adverse event?
Consumers and health professionals can report to FDA through MedWatch (Form FDA 3500 online, or 1-800-FDA-1088), or to the manufacturer, which must pass reports on. See the guide on how to report.
Where this comes from. Counts are built from the openFDA Drug Adverse Event (FAERS) bulk export released 28 Sep 2026, which holds reports FDA received through 30 Jun 2026. Drug names are as reported, resolved to the brand or generic name on the FDA label where openFDA's harmonisation matched them; classes are the pharmacologic class (EPC) from the label and the National Drug Code Directory of 17 Sep 2026. A report counts here when it lists Propylthiouracil as a suspect or interacting product; reports listing it only as a concomitant medication (929) are excluded. No report narrative, lot number, patient detail or reporter identity is published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.
Drug data (FAERS) through 30 Jun 2026; device data (MAUDE) through 31 Aug 2026. Not medical advice.