Trimethoprim-Sulfamethoxazole (TMP-SMX): Patient Guide
Trimethoprim-sulfamethoxazole is a combination antibiotic used to treat certain bacterial infections, including urinary tract, skin, intestinal, lung, and bone infections. It is also used to treat or prevent Pneumocystis jirovecii pneumonia in people with weakened immune systems.
Take this antibiotic exactly as prescribed and complete the full course unless a doctor tells you to stop. Contact a doctor or pharmacist before starting it if you are pregnant, have kidney or liver disease, or take other medicines.
Key facts at a glance
- ATC
- J01EE01
- Generic
- Trimethoprim-Sulfamethoxazole
- Class
- sulfonamide-combination
- Brands
- Bactrim, Septra
- Availability
- rx
- Pregnancy
- D
- Lactation
- unsafe
- Half-life (h)
- 10
- Onset (min)
- 60
- Duration (h)
- 12
- Routes
- oral, iv
- Forms
- tablet, injection
- Regions
- CN, US, EU, JP
- Monitoring
- renal-function, photosensitivity
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Dosage and administration
- Usual dose
- 500mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 250mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 400mg daily
- Maximum
- consult physician
- Frequency
- once daily
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
8 groupspregnancy
first trimesteravoid use
avoid use during first trimester due to teratogenic risk; folic acid antagonism may increase risk of neural tube defects, cardiovascular malformations, and cleft lip/palate
regular fetal monitoring including ultrasound for fetal anatomy
Use of this medication in this population requires careful consideration of risks and benefits.
pregnancy
third trimesteravoid use
avoid use near term (within 3 weeks of delivery) due to risk of kernicterus in newborns; sulfa displaces bilirubin from albumin
monitor newborn for signs of kernicterus
Use of this medication in this population requires careful consideration of risks and benefits.
lactation
breastfeedingcontraindicated
both trimethoprim and sulfamethoxazole pass into breast milk; contraindicated in breastfeeding due to risk of kernicterus in newborns and hemolytic anemia in G6PD-deficient infants
monitor infant for signs of jaundice, hemolytic anemia, and kernicterus
Use of this medication in this population requires careful consideration of risks and benefits.
pediatric_age
neonates and infantscontraindicated in infants less than 2 months
contraindicated in neonates and infants under 2 months of age due to risk of kernicterus; immature hepatic glucuronidation pathways and bilirubin displacement
monitor for signs of kernicterus including jaundice, lethargy, and poor feeding
Use of this medication in this population requires careful consideration of risks and benefits.
pediatric_age
children 2 months and olderweight-based dosing required
use with caution in children 2 months and older; contraindicated in children with G6PD deficiency; monitor for rash and hematologic adverse effects
monitor CBC periodically, watch for signs of rash, Stevens-Johnson syndrome
Use with caution and monitor for adverse effects.
geriatric
elderlyadjust based on renal function
use with caution in elderly patients; increased risk of adverse effects including bone marrow suppression, hyperkalemia, and renal impairment; increased mortality observed in some studies for trimethoprim component
monitor renal function (CrCl), serum potassium, and CBC regularly
Use with caution and monitor for adverse effects.
renal_impairment
mild to moderatereduce dose; use with caution in CrCl 30-50 mL/min
dose adjustment required; reduce dose by 50% for CrCl 15-30 mL/min; avoid use or use with extreme caution for CrCl <15 mL/min due to accumulation and toxicity risk
monitor renal function, serum electrolytes (especially potassium), and CBC
Use with caution and monitor for adverse effects.
hepatic_impairment
moderate to severeuse with caution
use with caution in hepatic impairment; trimethoprim is partially metabolized in liver; monitor liver function tests; avoid in severe hepatic impairment if possible
monitor liver function tests (ALT, AST, bilirubin) and clinical status
Use with caution and monitor for adverse effects.
Statistics and clinical data
FDA approval year
Initial FDA approval for Trimethoprim-Sulfamethoxazole
Drug class
Antimicrobial agent classification
Common uses
Primary therapeutic indications
Formulation type
Pharmaceutical formulation
Contraindications
Conditions and patient states where this medication should be avoided or used with caution.
Do not use (1)
Known allergy to this medication or its components
Use caution (1)
Consult healthcare provider for benefits vs risks assessment
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed July 22, 2026. · Read our editorial policy