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Pentosan (Systemic)

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Pentosan (Systemic)

US Brand Names

• Elmiron


Pentosan (PEN-toe-san) is used to relieve the symptoms of the bladder condition called interstitial cystitis.

This medicine is available only with your doctor's prescription, in the following dosage form:


    • Capsules (U.S. and Canada)

Special Considerations

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For pentosan, the following should be considered:


Tell your doctor if you have ever had any unusual or allergic reaction to pentosan. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.


It is important that you follow any special instructions from your doctor. Some foods and beverages may aggravate your condition. Also, make certain your health care professional knows if you are on any special diet, such as a low-sodium or low-sugar diet.


Pentosan has not been shown to cause birth defects or other problems in humans. However, studies in animal tissues have shown that pentosan may be harmful to the fetus. Before taking this medicine, make sure your doctor knows if you are pregnant or if you may become pregnant.


It is not known whether pentosan passes into breast milk. Although most medicines pass into breast milk in small amounts, many of them may be used safely while breast-feeding. Mothers who are taking this medicine and who wish to breast-feed should discuss this with their doctor.


Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of pentosan in children with use in other age groups.

Older adults

This medicine has been tested and has not been shown to cause different side effects or problems in older people than it does in younger adults.

Other medicines

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking pentosan, it is especially important that your health care professional know if you are taking any of the following:

    • Alteplase or

    • Anticoagulants (blood thinners) or

    • Aspirin, high doses or

    • Heparin or

    • Streptokinase-Taking these medicines with pentosan may increase the risk of bleeding

Other medical problems

The presence of other medical problems may affect the use of pentosan. Make sure you tell your doctor if you have any other medical problems, especially:

    • Blood or blood vessel disease or other blood problems or

    • Blockage or obstruction of the intestine or

    • Polyps or

    • Stomach ulcers-The risk of bleeding may be increased

    • Liver disease or

    • Spleen problems-Pentosan may not be broken down in the body as fast as it normally would; the chance of side effects may be increased


Take this medicine on an empty stomach (at least 1 hour before or 2 hours after meals) and at least 1 hour before or after any other food, milk, or medicine. Also, always take it with a full glass (8 ounces) of water.

Sometimes pentosan must be taken for up to 3 to 6 months before you begin to feel better. Your doctor should check your progress at regular visits during this time.


The dose of pentosan will be different for different patients. Follow your doctor's orders or the directions on the label . The following information includes only the average doses of pentosan. If your dose is different, do not change it unless your doctor tells you to do so.

    • For oral dosage form (capsules):

      o To treat interstitial cystitis:

        Adults-100 milligrams (mg) three times a day for three months. Your doctor may tell you to repeat this dose.

        Children-Use and dose must be determined by your doctor.

Missed dose

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.


To store this medicine:

    • Keep out of the reach of children.

    • Store away from heat and direct light.

    • Do not store in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.

    • Keep the medicine from freezing. Do not refrigerate.

    • Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.


This medicine may increase the risk of serious bleeding. Before having any kind of surgery or dental or emergency treatment, tell the medical doctor or dentist in charge that you are using this medicine.

It is important that you follow any special dietary instructions from your doctor. Some foods and beverages may aggravate your condition.

Side Effects

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

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


Chills; difficulty in breathing; fever; skin rash or hives; sore throat; unusual bleeding or brusing; unusual tiredness or weakness; vision impairment.

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

Less common or rare

Abdominal pain; bleeding gums; constipation; diarrhea; difficulty or pain upon swallowing; dizziness; dryness of throat; hair loss; headache; heartburn; increased sensitivity of skin to sunlight; irritated or red eyes; itching; loss of appetite; nausea; nosebleed; ringing in the ears; runny nose; sores in mouth; stomach gas; stomach upset; vomiting.

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.

May 20, 1998

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