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Treatments > Medications Used In MS

Brand Name Chemical Name

Bactrim; Septra
(U.S. and Canada)

Sulfamethoxazole (sul-fa-meth-ox-a-zole) and trimethoprim (try-meth-oh-prim) combination

Primary Usage in MS

Generic Available
Urinary Tract Infections Yes (U.S.)

Sulfamethoxazole and trimethoprim combination is used in multiple sclerosis to treat (and sometimes to prevent) urinary tract infections.

Proper Usage
This medication is best taken with a full glass (eight ounces) of water. Additional water should be taken each day to help prevent unwanted effects.

Finish the full course of treatment prescribed by your physician. Even if your symptoms disappear after a few days, stopping this medication prematurely may result in a return of the symptoms.

This medication works most effectively when it is maintained at a constant level in your blood or urine. To help keep the amount constant, do not miss any doses. It is best to take the doses at evenly spaced times during the day and night. For maximum effectiveness, four doses per day would be spaced at six-hour intervals.

This medication may cause dizziness.

If taken for a long time, sulfamethoxazole and trimethoprim combination may cause blood problems. It is very important that your physician monitor your progress at regular visits.

This medication can cause changes in the blood, possibly resulting in a greater chance of certain infections, slow healing, and bleeding of the gums. Be careful with the use of your toothbrush, dental floss, and toothpicks. Delay dental work until your blood counts are completely normal. Check with your dentist if you have questions about oral hygiene during treatment.

This medication may cause your skin to become more sensitive to sunlight. Stay out of direct sunlight during the midday hours, wear protective clothing, and apply a sun block product that has a skin protection factor (SPF) of at least 15.

Sulfamethoxazole and trimethoprim combination has not been reported to cause birth defects or other problems in humans. Studies in mice, rats, and rabbits have shown that some sulfonamides cause birth defects, including cleft palate and bone problems. Studies in rabbits have also shown that trimethoprim causes birth defects, as well as a decrease in the number of successful pregnancies.

Sulfamethoxazole and trimethoprim pass into breast milk. This medication is not recommended for use during breastfeeding. It may cause liver problems, anemia, and other problems in nursing babies.

Possible Side Effects
Side effects that may go away as your body adjusts to the medication and do not require medical attention unless they continue or are bothersome: diarrhea; dizziness; headache; loss of appetite; nausea or vomiting.

Less common side effects that should be reported to your physician immediately: itching; skin rash; aching of muscles and joints; difficulty in swallowing; pale skin; redness, blistering, peeling, or loosening of skin; sore throat and fever; unusual bleeding or bruising; unusual tiredness or weakness*; yellow eyes or skin.

*Since it may be difficult to distinguish between certain common symptoms of MS and some side effects of sulfamethoxazole, be sure to consult your health care professional if an abrupt change of this type occurs.

Medication Index

Other Medications Used to Treat Urinary Tract Infections

Read more on bladder dysfunction and learn management strategies to help live comfortably.

Reprinted with permission from Rosalind C. Kalb (ed.), Multiple Sclerosis: The Questions You Have—The Answers You Need (4th ed.). New York: Demos Medical Publishing, 2007.

Last updated September 20, 2007