Elmiron Side Effects

Most Elmiron side effects are mild and stop after the body gets used to the medication. Many people tolerate the medication well. Vision loss symptoms from Elmiron vary but here are the most common symptoms. Some long-term users of Elmiron have experienced vision problems.

Researchers studied Elmiron side effects in 2,627 patients, according to the drug’s prescribing information. Common side effects occurred in 1% to 4% of participants. Thirty-three patients, about 1.3%, suffered serious side effects. Six patients died, but other health problems appear to have caused the deaths.

The most common side effect reported was hair loss, or alopecia. Hair loss began in the first four weeks of treatment. About 97% of patients experienced hair loss in a single spot. Hair loss stopped for most patients and hair grew back after they discontinued using the drug.

In an unblended clinical trial of 2,499 patients with interstitial cystitis, the most prevalent side effects included hair loss (4%), diarrhea (4%), nausea (4%), headache (3%) and rash (3%).

In clinical trials, a year was the longest researchers followed trial participants.

Does Elmiron Cause Weight Gain?

As of June 2020, Elmiron’s prescription information does not list weight gain as a side effect.

An October 2017 patient flyer indicated “weight gain and swelling caused by fluid buildup have been reported in patients taking Elmiron.” In animal study data, mice who took higher doses of the drug had a “significant increase (40%) in body weight gain,” according to a March 2016 European Medicines Agency assessment report of Elmiron.

According to the drug’s prescribing information, rare side effects happened in 1% or less of the trial participants. Though rare, some of these side effects have been serious, including rectal hemorrhage and abnormal liver function.

Abnormal liver function may be associated with Elmiron. In a phase 2 study, six out of 51 patients (11.8%) had increases in their liver function tests with a daily dose of 900 mg.

Rectal hemorrhage was reported in a phase 4 study of 128 patients. Eight patients (6.3%) who took the daily 300 mg dose experienced rectal hemorrhage, but most patients described it as mild. Among people who took a 900 mg dose, 15% had a higher incidence of rectal bleeding.

In June 2020, Janssen Pharmaceuticals added a warning for retinal pigmentary changes, also known as pigmentary maculopathy, associated with long-term Elmiron use. Increased dose and length of use appear to be risk factors.

The cause of the disease is not clear. Most cases happened in people who used the drug for three years or longer. However, people who used the drug for shorter durations have also reported symptoms.

The prescribing information recommends vision tests within six months of starting treatment and periodic tests after that. Some people continued to have progressive vision damage after stopping treatment.

One March 2022 study in the British Journal of Clinical Pharmacology found that people who used Elmiron for more than three years had a 9.5-fold increased risk of maculopathy compared to a 2.3-fold increased risk with use of one year or less.

People who experienced vision damage filed Elmiron lawsuits against Janssen Pharmaceuticals. Lawsuits claim the drugmaker failed to warn them about the risk.

A search of the postmarketing data available on the FDA Adverse Event Reporting System (FAERS) Public Dashboard for “Elmiron” and “pentosan polysulfate sodium” from 1997 to June 30, 2020, showed 2,570 adverse event reports.

Of those reports, 1,748 were serious, including 24 deaths. Data on FAERS comes from voluntary reports and the FDA cannot verify if the adverse event was related to drug use. There were 202 eye disorders reported. These included maculopathy, visual impairment and blurred vision.