Trimethoprim
Trimethoprim is a synthetic antibiotic used to treat various bacterial infections by inhibiting bacterial growth. It is commonly prescribed for urinary tract infections and may be used alone or in combination with other antibiotics for other conditions.
Trimethoprim is an antibiotic that treats bacterial infections, particularly urinary tract infections, by preventing bacteria from multiplying.
Key facts at a glance
- ATC
- J01EA01
- RxNorm
- 10829
- Generic
- Trimethoprim
- Class
- atc-j01
- Brands
- Bactrim, Equisul SDT, Sulfatrim, Primsol, Uniprim
- Availability
- rx
- Lactation
- unknown
- Routes
- oral, ophthalmic
- Forms
- injection, tablet, solution, powder, suspension
- 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
- 100mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 4-6mg/kg once daily
- Maximum
- consult physician
- Frequency
- once daily
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 100mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
8 groupspregnancy
first trimesteravoid if possible
avoid use during pregnancy unless benefits outweigh risks. Trimethoprim is a folate antagonist and may cause birth defects.
regular fetal monitoring
Use of this medication in this population requires careful consideration of risks and benefits.
pregnancy
second and third trimesteruse lowest effective dose
use only if benefits outweigh risks. Folate supplementation may reduce risk.
regular prenatal checkups
Use with caution and monitor for adverse effects.
lactation
breastfeedingavoid
do not breastfeed while taking trimethoprim. Drug passes into breast milk.
monitor infant for adverse effects
Use of this medication in this population requires careful consideration of risks and benefits.
geriatric
elderlyadjust dose based on renal function
use with caution due to age-related decline in renal function. Monitor renal function regularly.
monitor renal function and for signs of adverse effects
Use with caution and monitor for adverse effects.
pediatric_age
infants and childrenweight-based dosing required
use pediatric formulation. Standard dose is 8-12 mg/kg/day divided every 12 hours.
monitor for adverse effects and response to therapy
renal_impairment
mild to moderatereduce dose
adjust dose based on CrCl. For CrCl 15-30 mL/min, use half the standard dose.
monitor renal function and serum drug levels if available
Use with caution and monitor for adverse effects.
renal_impairment
severeavoid
do not use in patients with CrCl less than 15 mL/min
not applicable
Use of this medication in this population requires careful consideration of risks and benefits.
hepatic_impairment
mild to moderateno specific adjustment
use with caution. No standard dose adjustment but monitor liver function.
monitor liver function tests
Use with caution and monitor for adverse effects.
Statistics and clinical data
Commonly prescribed since
General prescribing information
Drug class
Drug class information
Common uses
Common therapeutic uses
Common formulations
Available dosage forms
Trimethoprim is primarily used to treat uncomplicated urinary tract infections (UTIs). It may also be used for acute otitis media (ear infections), acute exacerbations of chronic bronchitis, and traveler's diarrhea. In some cases, it is combined with sulfamethoxazole for enhanced抗菌效果.
Trimethoprim works by inhibiting the bacterial enzyme dihydrofolate reductase, which is essential for the synthesis of folic acid in bacteria. This blocks nucleotide synthesis, preventing bacterial DNA replication and growth.
Trimethoprim may cause side effects such as nausea, vomiting, skin rash, and photosensitivity. It should be used with caution in patients with kidney or liver impairment, and is generally avoided during pregnancy, particularly in the first trimester. Patients should complete the full course of treatment as prescribed.
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