Mitomycin C is a chemotherapy drug that works by damaging the DNA of rapidly dividing cells, preventing them from multiplying. Originally derived from a soil bacterium, it has been used in cancer treatment for decades and also plays a surprisingly common role in eye surgery. Its versatility makes it one of the more unusual drugs in medicine: depending on the situation, it can be delivered intravenously, instilled directly into the bladder, or applied as eye drops.
How Mitomycin C Works
Mitomycin C belongs to a class of drugs called alkylating agents. Once inside the body, it undergoes a chemical activation process that allows it to bind directly to DNA strands. Specifically, it creates cross-links between the two strands of the DNA double helix, essentially gluing them together so the cell can no longer copy its genetic material. A cell that cannot replicate its DNA cannot divide, and it eventually dies.
This mechanism is particularly effective against cancer cells because they divide much faster than most normal cells. However, it is not perfectly selective. Mitomycin C also affects healthy cells that divide quickly, like those in bone marrow and the lining of the digestive tract, which is the root cause of most of its side effects.
Cancer Treatment Uses
Mitomycin C is used against several types of cancer, but its most well-known application is in bladder cancer. For non-muscle invasive bladder cancer, the drug is delivered directly into the bladder through a catheter rather than into the bloodstream. This approach, called intravesical therapy, concentrates the drug right where the tumor is while limiting exposure to the rest of the body.
In June 2025, the FDA approved a dedicated intravesical solution of mitomycin specifically for adults with recurrent low-grade, intermediate-risk non-muscle invasive bladder cancer. The approved dose is 75 mg instilled once weekly for six weeks. Older intravesical regimens typically use 20 to 40 mg diluted in saline or a buffer solution, instilled weekly or multiple times per week depending on whether the goal is treatment or prevention of recurrence.
When given intravenously for other cancers, doses generally range from 10 to 20 mg per square meter of body surface area, administered every six to eight weeks. The exact schedule depends on the specific cancer being treated and what other drugs are part of the regimen.
Use in Eye Surgery
Outside of oncology, mitomycin C has a second life as a tool in ophthalmic surgery. Because it stops cells from dividing, it can prevent scar tissue from forming after procedures on the eye. Surgeons apply it topically at very low concentrations, typically 0.04%, during or after operations for pterygium (a fleshy growth on the surface of the eye) and certain types of glaucoma surgery. For pterygium, the drug may be given as eye drops four times daily for two weeks after the growth is removed, reducing the chance it will grow back.
The concentrations used in eye surgery are far lower than those used in cancer treatment, but the principle is the same: slowing down cell growth at the surgical site to get a cleaner, longer-lasting result.
What Bladder Treatment Feels Like
If you are receiving intravesical mitomycin C for bladder cancer, the process is straightforward but requires a weekly hospital visit. A thin catheter is inserted into the bladder, the drug solution is instilled, and the catheter is removed. You then hold the solution in your bladder for a set period before urinating it out. This cycle repeats once a week for six weeks in a standard course.
The direct-to-bladder approach means you avoid many of the systemic side effects associated with intravenous chemotherapy, like significant hair loss or severe nausea. Local irritation of the bladder is the most common complaint, and some people experience a burning sensation during urination or an increased urge to urinate in the hours following treatment.
Side Effects of Systemic Treatment
When mitomycin C is given intravenously, the side effect profile is more serious. The most significant risk is bone marrow suppression, which means the drug reduces the body’s ability to produce blood cells. This can lead to a higher risk of infection (from low white blood cells), unusual bleeding or bruising (from low platelets), and fatigue (from low red blood cells). Fever, sore throat, or persistent cough during treatment are warning signs that blood cell counts may have dropped too low.
Common, less severe side effects include nausea, vomiting, loss of appetite, mouth sores, headache, hair loss, and general fatigue. Skin reactions near the injection site, including pain, redness, blistering, or tissue damage, can occur if the drug leaks out of the vein during infusion.
A rare but potentially life-threatening complication is hemolytic uremic syndrome, a condition where red blood cells are damaged, leading to anemia and kidney problems. Symptoms to watch for include bloody stools, decreased urination, swelling in the face or limbs, and unusual weakness. This complication is uncommon, but it requires immediate medical attention.
Safety Around the Drug
Mitomycin C is classified as a hazardous substance, and strict safety protocols govern how it is handled in hospitals and pharmacies. Healthcare workers who prepare or administer the drug wear protective gloves, gowns, and eye protection. It is mixed inside specialized ventilated cabinets designed to prevent airborne exposure. Contaminated clothing cannot be taken home, and any spills are cleaned with wet methods rather than dry sweeping, which could spread the drug as dust.
For patients, the practical implications are minimal since healthcare staff manage the preparation. If you are receiving intravesical treatment, you may be advised to flush the toilet twice after urinating for a period following each instillation, and to wash your hands thoroughly, since trace amounts of the drug will be present in your urine.