What is the generic name for Bactrim (sulfamethoxazole‑trimethoprim)?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: October 25, 2026 • View editorial policy

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.

Ask Question

Generic Name for Bactrim

The generic name for Bactrim is sulfamethoxazole-trimethoprim (also written as sulfamethoxazole/trimethoprim or abbreviated as SMX-TMP or ST). 1

Composition Details

Bactrim is a fixed-dose combination antibiotic containing two active ingredients 1:

  • Sulfamethoxazole: A sulfonamide antibiotic (molecular formula C₁₀H₁₁N₃O₃S)
  • Trimethoprim: A dihydrofolate reductase inhibitor (molecular formula C₁₄H₁₈N₄O₃)

Available Formulations

The medication comes in standardized ratios 1:

  • Double Strength (DS) tablets: 800 mg sulfamethoxazole + 160 mg trimethoprim
  • Regular strength tablets: 400 mg sulfamethoxazole + 80 mg trimethoprim
  • Small tablets (sTab): 4 small tablets = 1 conventional tablet 2

Clinical Context

This combination antibiotic is used for multiple bacterial infections including urinary tract infections, acute otitis media, traveler's diarrhea, Shigella infections, and Pneumocystis jirovecii pneumonia prophylaxis 1. The generic formulation is widely available and functions identically to the brand name Bactrim, as both contain the same active pharmaceutical ingredients in the same ratios.

When prescribing or dispensing, either "sulfamethoxazole-trimethoprim" or the abbreviation "SMX-TMP" can be used interchangeably with the brand name Bactrim 3, 4.

References

Related Questions

How many tablets of Bactrim (sulfamethoxazole/trimethoprim) should be administered?
Can 500 mL of intravenous sulfamethoxazole/trimethoprim (Bactrim) be infused over one hour?
Can Bactrim DS (sulfamethoxazole/trimethoprim) tablets be crushed?
Can sulfamethoxazole‑trimethoprim cause a change in taste?
What is the appropriate daily volume of liquid sulfamethoxazole/trimethoprim (200 mg/40 mg per 5 mL) for a child weighing 62.6 kg to achieve a trimethoprim dose of 40 mg/kg/day?
What is the appropriate dosage of ashwagandha for treating anxiety?
Does buspirone (Buspar) interact with melatonin?
Can L‑theanine be added safely to an adult patient taking buspirone for anxiety and melatonin for sleep?
Can 5‑HTP be taken safely with Wellbutrin (bupropion)?
Why can bumetanide and torsemide be administered concurrently?
What is the best sleep aid to use with buspirone and bupropion?

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.