Sulfamethoxazole
Sulfamethoxazole is a sulfonamide-type antibiotic used to treat a variety of bacterial infections. It works by inhibiting the production of folic acid in bacteria, which is essential for their growth and survival. This medication is commonly prescribed for urinary tract infections, respiratory infections, and gastrointestinal infections.
Sulfamethoxazole is an antibiotic that treats bacterial infections by blocking folic acid production in bacteria.
Key facts at a glance
- ATC
- J01EC01
- RxNorm
- 10180
- Generic
- Sulfamethoxazole
- Class
- atc-j01
- Brands
- Bactrim, Sulfatrim
- Availability
- rx
- Lactation
- unknown
- Routes
- oral
- Forms
- injection, tablet, suspension, solution
- Regions
- US, EU, CN, JP
- Monitoring
- —
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
10 groupspregnancy
first trimesteravoid if possible
avoid use during pregnancy unless benefits outweigh risks, particularly in first trimester
regular prenatal monitoring
Use with caution and monitor for adverse effects.
pregnancy
third trimesteravoid
avoid use near term (within 2 weeks of delivery)
fetal monitoring
Use of this medication in this population requires careful consideration of risks and benefits.
lactation
breastfeedingavoid
do not breastfeed during treatment with sulfamethoxazole
monitor infant for signs of kernicterus
Use of this medication in this population requires careful consideration of risks and benefits.
geriatric
elderlydose adjustment based on renal function
use with caution, monitor renal function, consider dose reduction in renal impairment
regular renal function monitoring, watch for adverse effects
Use with caution and monitor for adverse effects.
pediatric_age
neonatesavoid
do not use in newborns, especially premature infants
monitor for kernicterus symptoms
Use of this medication in this population requires careful consideration of risks and benefits.
pediatric_age
infants and childrendose adjustment required
use with caution, typically reserved for specific infections, ensure adequate hydration
monitor for skin reactions, blood counts
Use with caution and monitor for adverse effects.
renal_impairment
mild to moderatedose reduction required
reduce dose or extend dosing interval in renal impairment, monitor renal function
regular renal function monitoring, serum drug levels if available
Use with caution and monitor for adverse effects.
renal_impairment
severesignificant dose reduction or avoid
use with extreme caution or avoid in severe renal impairment (CrCl < 30 mL/min)
close monitoring of renal function, consider therapeutic drug monitoring
Use of this medication in this population requires careful consideration of risks and benefits.
hepatic_impairment
mild to moderateno specific adjustment
use with caution, monitor liver function
regular liver function tests
Use with caution and monitor for adverse effects.
hepatic_impairment
severeavoid
avoid use in severe hepatic impairment
liver function monitoring
Use of this medication in this population requires careful consideration of risks and benefits.
Statistics and clinical data
Commonly prescribed since
General prescribing information for sulfamethoxazole/trimethoprim combination
Drug class
Antibiotic classification
Common uses
Common therapeutic uses
Sulfamethoxazole is used to treat urinary tract infections, bronchitis, ear infections, traveler's diarrhea, and certain types of pneumonia. It is particularly effective against susceptible strains of E. coli, Proteus, and Staphylococcus bacteria.
As a sulfonamide antibiotic, sulfamethoxazole inhibits bacterial dihydropteroate synthase, an enzyme involved in the synthesis of folic acid. This disrupts bacterial DNA synthesis and prevents the bacteria from multiplying and spreading.
Common side effects include nausea, vomiting, and skin rashes. Patients with sulfa allergies, pregnant women in late pregnancy, or individuals with severe kidney or liver disease should avoid this medication. Adequate fluid intake is recommended during treatment to prevent crystal formation in the urine.
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 August 24, 2026. · Read our editorial policy