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Elmiron Side Effects

The three most common Elmiron (pentosan polysulfate sodium) side effects are hair loss, diarrhea and nausea. More serious side effects that require hospitalization, such as severe abdominal pain and dehydration, are rare. In June 2020, Janssen Pharmaceuticals added a warning for retinal pigmentary maculopathy, a condition that causes vision problems.

Elmiron treats interstitial cystitis (IC), a condition that affects more women than men and causes pain and pressure in the bladder. Most Elmiron side effects are mild and stop after the body gets used to the medication. Most people tolerate the medication well.

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

Common Side Effects

Researchers studied Elmiron side effects in 2,627 patients, according to the drug’s prescribing information. Common side effects occurred in 1 to 4 percent of participants. Thirty-three patients, about 1.3 percent, 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 percent of patients who reported cases of alopecia experienced hair loss on a single spot. This usually went away after patients stopped using the drug and hair grew back.

Common side effects in an unblended clinical trial of 2,499 patients with interstitial cystitis include:
  • Hair Loss (4 percent)
  • Diarrhea (4 percent)
  • Nausea (4 percent)
  • Headache (3 percent)
  • Rash (3 percent)
  • Dyspepsia (abdominal discomfort, indigestion) (2 percent)
  • Abdominal pain (2 percent)
  • Abnormal liver function tests (1 percent)
  • Dizziness (1 percent)

Does Elmiron Cause Weight Gain?

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

However, an October 2017 patient flyer says that “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 assessment report of Elmiron by the European Medicines Agency.

Rare Side Effects

According to the drug’s prescribing information, rare side effects happened in one percent or less of the trial participants.

Rare side effects include:
  • Allergic reactions and photosensitivity
  • Anemia and other blood abnormalities
  • Cold-like symptoms
  • Colitis constipation
  • Conjunctivitis (pink eye)
  • Itchy skin
  • Mouth ulcers
  • Retinal hemorrhage
  • Ringing in the ears (tinnitus)
  • Shortness of breath
  • Vomiting

Rectal Hemorrhage

In a phase 4 study of 128 patients, 8 patients (6.3 percent) who took the daily 300 mg dose experienced rectal hemorrhage. Most patients described it as mild. Fifteen percent of patients who took a 900 mg dose had a higher incidence of rectal bleeding.

Abnormal Liver Function

In a phase 2 study, 6 out 51 patients (11.8 percent) had increases in their liver function tests with a daily dose of 900 mg.

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Vision Damage

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, but people who used the drug for shorter durations have also reported symptoms.

Vision changes in reported cases include:
  • Slow adjustment to low light
  • Difficulty reading
  • Blurred vision

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.

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

Side Effects Reported to FDA

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.

The top five adverse events in FAERS were:
  • Alopecia, 252
  • Headache, 173
  • Diarrhea, 166
  • Nausea, 156
  • Dizziness, 120
Elmiron Pill
Elmiron Side Effects Facts
  1. Most Common Side Effects Hair loss, nausea, diarrhea, headache, blood in the stool, rash, abnormal liver function tests, upset stomach, bruising and dizziness
  2. Rare Side Effects Vision problems, rectal bleeding, anemia, itchy skin, mouth ulcers, retinal hemorrhage, constipation
  3. Pregnancy Safety Animal studies didn’t reveal impaired fertility or harm to the fetus, but adequate studies have not been performed in pregnant women. Pregnant women should only use the drug if clearly needed.
  4. Warnings Retinal pigmentary changes

Please seek the advice of a medical professional before making health care decisions.

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Michelle Llamas, Senior Content Writer
Written By Michelle Llamas Senior Writer

Michelle Llamas has been writing articles and producing podcasts about drugs, medical devices and the FDA for nearly a decade. She focuses on various medical conditions, health policy, COVID-19, LGBTQ health, mental health and women’s health issues. Michelle collaborates with experts, including board-certified doctors, patients and advocates, to provide trusted health information to the public. Some of her qualifications include:

  • Member of American Medical Writers Association (AMWA) and former Engage Committee and Membership Committee member
  • Centers for Disease Control and Prevention (CDC) Health Literacy certificates
  • Original works published or cited in The Lancet, British Journal of Clinical Pharmacology and the Journal for Palliative Medicine
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  1. European Medicines Agency. (2016, March 23). Elmiron Assessment Report. Retrieved from
  2. Janssen Pharmaceuticals. (2017). Interstitial Cystitis and Elmiron. Retrieved from
  3. Janssen Pharmaceuticals. (2020, June). Elmiron Prescribing Information. Retrieved from
  4. Janssen Pharmaceuticals. (n.d.). Elmiron. Retrieved from
  5. U.S. Food and Drug Administration. (2020, June 30). FDA Adverse Event Reporting System (FAERS) Public Dashboard. Retrieved from
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