Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes Elmiron (Pentosan). If you are concerned about side effects, discuss the risks and benefits of Elmiron (Pentosan) with your doctor.

The following side effects have been reported by at least 1% of people taking Elmiron (Pentosan). Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• abdominal pain
• Diarrhea
• dizziness
• hair loss
• headache
• itching
• nausea
• rash

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• shortness of breath
• signs of clotting problems (e.g., unusual nosebleeds, bruising, blood in urine, rectal bleeding, coughing blood, bleeding gums, cuts that don't stop bleeding)
• skin rash or Hives
• vision changes (difficulty reading, slow adjustment to decreased light, wavy or blurred vision)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking Elmiron (Pentosan).