What the label lists and what reports show
Mitomycin side effects
Mitomycin's FDA label: “Bone Marrow Toxicity This was the most common and most serious toxicity, occurring in 605 of 937 patients (64.4%).” FAERS holds 3,418 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is nausea (170 reports).
- Generic listed
- Boxed warning
Check it at the source: the mitomycin FDA label on DailyMed (effective April 22, 2025, Accord Healthcare, Inc.); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of JELMYTO?JELMYTO may cause serious side effects, including: Swelling and narrowing of the tube that carries urine from the kidney to the bladder (ureteric obstruction). If you develop swelling and narrowing, and to protect your kidney from damage, your healthcare provider may recommend the placement of a small plastic tube (stent) in the ureter to help the kidney drain. Tell your healthcare provider right away if you develop side pain or fever during treatment with JELMYTO. Bone marrow problems. JELMYTO can affect your bone marrow and can cause a decrease in your white blood cell, red blood cell, and platelet counts. Your healthcare provider will do blood tests prior to each treatment to check your blood cell counts during treatment with JELMYTO. Your healthcare provider may need to temporarily or permanently stop JELMYTO if you develop bone marrow problems during treatment with JELMYTO. […]
Source: FDA drug label (JELMYTO), UroGen Pharma, Inc., effective July 9, 2025 (SPL set 3d3d5053-5427-4a68-a40b-edb60699521e), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsBone Marrow Toxicity This was the most common and most serious toxicity, occurring in 605 of 937 patients (64.4%).
Table 1: Adverse Reactions (≥ 10% All Grades) in Patients Who Received JELMYTO in Olympus
This table is printed in the JELMYTO label published by UroGen Pharma, Inc. of July 9, 2025; the label quoted above does not print one.
| Adverse Reaction | All Grades (%) | Grade 3-4 (%) |
|---|---|---|
| Ureteric Obstruction Includes hydronephrosis, obstructive uropathy, pelvi-ureteric… | 58 | 17 |
| Ureteric stenosis | 44 | 9 |
| Hydronephrosis | 18 | 6 |
| Urinary tract obstruction | 7 | 1.4 |
| Pelvi-ureteric obstruction | 6 | 1.4 |
| Ureteric obstruction | 2.8 | 1.4 |
| Obstructive uropathy | 1.4 | 0 |
| Flank pain Includes flank pain and back pain. | 41 | 2.8 |
| Hematuria Includes hematuria and hemorrhage urinary tract. | 34 | 2.8 |
| Urinary tract infection Includes urinary tract infection, pyelonephritis, and urinary… | 34 | 4.2 |
| Renal dysfunction Includes renal impairment, acute kidney injury, and renal failure. | 25 | 2.8 |
| Dysuria | 23 | 0 |
| Pollakiuria | 14 | 0 |
| Nausea | 25 | 1.4 |
| Abdominal pain Includes abdominal pain and abdominal pain lower. | 24 | 1.4 |
| Vomiting | 20 | 4.2 |
| Fatigue Includes asthenia, fatigue, and malaise. | 24 | 1.4 |
| Pyrexia | 13 | 1.4 |
| Chills | 11 | 0 |
| Anemia | 14 | 1.4 |
| Rash Includes rash, dermatitis allergic, rash generalized, genital rash, eczema, rash… | 14 | 0 |
| Pruritus | 13 | 0 |
| Decreased appetite | 10 | 0 |
| Hypertension | 10 | 4.2 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedBone Marrow Toxicity This was the most common and most serious toxicity, occurring in 605 of 937 patients (64.4%). Thrombocytopenia and/or leukopenia may occur anytime within 8 weeks after onset of therapy with an average time of 4 weeks. Recovery after cessation of therapy was within 10 weeks. About 25% of the leukopenic or thrombocytopenic episodes did not recover. Mitomycin produces cumulative myelosuppression. Integument and Mucous Membrane Toxicity This has occurred in approximately 4% of patients treated with mitomycin. Cellulitis at the injection site has been reported and is occasionally severe. Stomatitis and alopecia also occur frequently. Rashes are rarely reported. The most important dermatological problem with this drug, however, is the necrosis and consequent sloughing of tissue which results if the drug is extravasated during injection. Extravasation may occur with or without an accompanying stinging or burning sensation and even if there is adequate blood return when the injection needle is aspirated. There have been reports of delayed erythema and/or ulceration occurring either at or distant from the injection site, weeks to months after mitomycin, even when no obvious evidence of extravasation was observed during administration. Skin grafting has been required in some of the cases. …
Source: FDA drug label, Accord Healthcare, Inc., effective April 22, 2025 (SPL set ff676355-313d-4575-8f2f-e4a1e9527477), via openFDA; the full label on DailyMed
What do FAERS reports show?
3,418 reports list mitomycin among the medicines taken, each a report of something that happened, not proof the medicine caused it; 392 are coded as a death and 983 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 20 reactions below, 13 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Mitomycin: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions