It is important that your doctor check your progress at regular visits if you will be taking this medicine for a long time. This will allow your doctor to check for any unwanted effects that may be caused by this medicine.
If your symptoms do not improve within a few days, or if they become worse, check with your doctor.
If this medicine causes anemia, your doctor may want you to take folic acid (a vitamin) every day to help clear up the anemia. If so, it is important to take folic acid every day along with this medicine; do not miss any doses.
Trimethoprim may cause blood problems. These problems may result in a greater chance of certain infections, slow healing, and bleeding of the gums. Therefore, you should be careful when using regular toothbrushes, dental floss, and toothpicks. Dental work should be delayed until your blood counts have returned to normal. Check with your medical doctor or dentist if you have any questions about proper oral hygiene (mouth care) during treatment.
Some people who take trimethoprim may become more sensitive to sunlight than they are normally. Exposure to sunlight, even for brief periods of time, may cause severe sunburn or skin rash, redness, itching, or discoloration. When you begin taking this medicine:
- Stay out of direct sunlight, especially between the hours of 10:00 a.m. and 3:00 p.m., if possible.
- Apply a sun block product that has a skin protection factor (SPF) of at least 15. Some patients may require a product with a higher SPF number, especially if they have a fair complexion. If you have any questions about this, check with your health care professional.
- Do not use a sunlamp or tanning bed or booth.
If you have a severe reaction from the sun, check with your doctor.