Worst Pills, Best Pills

An expert, independent second opinion on more than 1,800 prescription drugs, over-the-counter medications, and supplements

Drug Profile

The information on this site is intended to supplement and enhance, not replace, the advice of a physician who is familiar with your medical history. Decisions about your health should always be made ONLY after detailed conversation with your doctor.

Generic drug name: trimethoprim (trye METH o prim)
Brand name(s): GENERIC VERSIONS ONLY
GENERIC: available FAMILY: Other Drugs for Bacterial Infection
Find the drug label by searching at DailyMed.

Pregnancy and Breast-feeding Warnings [top]

Pregnancy Warning

This drug crossed the placenta and caused malformations in developing fetuses in animal studies. Use during pregnancy only for clear medical reasons. Tell your doctor if you are pregnant or thinking of becoming pregnant before you take this drug.

Breast-feeding Warning

Trimethoprim is excreted in human milk at concentrations equal to or greater than the mother’s serum and may interfere with folic acid metabolism in nursing infants. Because of the potential for serious adverse effects in nursing infants, you should not take this drug while nursing.

Facts About This Drug [top]

Trimethoprim is approved by the FDA for the treatment of initial episodes of uncomplicated urinary tract infections.[1] It will not help a cold or the flu.

If you have severe kidney impairment, you should use caution in taking trimethoprim.[2] If you have impaired kidney function, you may need to take less than the usual adult dose. While taking trimethoprim, you may suffer a rash or itching.

Trimethoprim has been linked to birth defects, including spinal cord abnormalities, cleft...

Trimethoprim is approved by the FDA for the treatment of initial episodes of uncomplicated urinary tract infections.[1] It will not help a cold or the flu.

If you have severe kidney impairment, you should use caution in taking trimethoprim.[2] If you have impaired kidney function, you may need to take less than the usual adult dose. While taking trimethoprim, you may suffer a rash or itching.

Trimethoprim has been linked to birth defects, including spinal cord abnormalities, cleft palate and heart malformations, in children born to women who used trimethoprim during the first trimester.[3] Some  of these defects are likely due to the drug’s ability to interfere with folic acid.

Practice measures to prevent urinary tract infections. Drink plenty of fluids, especially water. While cranberry juice is unreliable as a cure for urinary tract infections, the juice may reduce odor from incontinence.[4] Practice meticulous hygiene. After using the toilet, wipe backward, not forward, then wash your hands. Prepare and store foods properly, especially when traveling, to prevent diarrhea. Restrict caffeine, which widens the urethra. Indwelling bladder catheters invite urinary tract infections. However, unless there are symptoms of urinary infection, it is not always necessary to take medication just because bacteria are found in a urine test.[5] Women are particularly prone to repeated urinary tract infections. If urinary tract symptoms occur often, ask your doctor about keeping a supply of medication on hand. Ideally, the antibiotic you use should be the most effective, least toxic, and least costly.[6],[7]

Before You Use This Drug [top]

Tell your doctor if you have or have had:

  • pregnancy or are breast-feeding
  • an unusual reaction to trimethoprim
  • folic acid (folate) deficiency
  • kidney or liver problems
  • anemia

Tell your doctor about any other drugs you take, including aspirin, herbs, vitamins, and other nonprescription products.

When You Use This Drug [top]

  • If you plan to have any surgery, including dental, tell your doctor that you take this drug.
  • Check with your doctor or dentist concerning proper technique in taking care of your teeth.
  • Check with your doctor if there is no improvement within a few days.
  • Have regular visits with your doctor to check on your progress.
  • If you take trimethoprim for a long time, ask your doctor if you need a folic acid supplement.
  • Stay out of the sun.

How to Use This Drug [top]

  • If you miss a dose, take it as soon as you remember, but skip it if it is almost time for the next dose. Do not take double doses.
  • Do not share your medication with others.
  • Take the drug at the same time(s) each day.
  • Take without food unless you have stomach irritation, then take with food.
  • For tablets: Store at room temperature with lid on tightly. Do not store in the bathroom. Do not expose to heat, moisture, or strong light. Keep out of reach of children.
  • Take this drug for the prescribed length of time. If you stop too soon, your symptoms could come back.

Interactions with Other Drugs [top]

The following drugs, biologics (e.g., vaccines, therapeutic antibodies), or foods are listed in Evaluations of Drug Interactions 2003 as causing “highly clinically significant” or “clinically significant” interactions when used together with any of the drugs in this section. In some sections with multiple drugs, the interaction may have been reported for one but not all drugs in this section, but we include the interaction because the drugs in this section are similar to one another. We have also included potentially serious interactions listed in the drug’s FDA-approved professional package insert or in published medical journal articles. There may be other drugs, especially those in the families of drugs listed below, that also will react with this drug to cause severe adverse effects. Make sure to tell your doctor and pharmacist the drugs you are taking and tell them if you are taking any of these interacting drugs:

COUMADIN, DILANTIN, dofetilide, methotrexate, phenytoin, TREXALL DOSE PACK, TIKOSYN, warfarin.

Adverse Effects [top]

Call your doctor immediately if you experience:

  • chills, fever, or sore throat
  • abnormal bleeding or bruising
  • abnormal paleness, tiredness, or weakness
  • bluish fingernails, lips, or skin
  • trouble breathing
  • headache
  • nausea
  • neck stiffness
  • shortness of breath
  • swelling of face
  • changes in facial skin color
  • pale skin
  • skin rash or itching
  • joint and muscle pain
  • skin red, blistering, or peeling
  • redness, swelling, or soreness of tongue
  • black, tarry stools
  • blood in urine
  • pinpoint red spots on skin
  • red skin lesions, often with a purple center

Call your doctor if these symptoms continue:

  • unusual taste in mouth
  • diarrhea
  • loss of appetite
  • nausea or vomiting
  • sore mouth or tongue
  • stomach cramps or pain
  • headache

Signs of overdose:

  • chills
  • fever
  • sore throat
  • unusual tiredness or weakness
  • unusual bleeding or bruising
  • black, tarry stools
  • blood in urine
  • pinpoint red spots on skin
  • confusion
  • dizziness
  • headache
  • depression
  • nausea or vomiting

If you suspect an overdose, call this number to contact your poison control center: (800) 222-1222.

Periodic Tests[top]

Ask your doctor which of these tests should be done periodically while you are taking this drug:

  • complete blood count

 

last reviewed April 30, 2021