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Trimethoprim/Sulfamethoxazole (Bactrim)

Antibioticprescriptionoral · inferred

Fixed 1:5 ratio combination (TMP 160 mg / SMX 800 mg in DS tablet) providing sequential blockade of folate synthesis, sulfamethoxazole inhibits dihydropteroate synthase, trimethoprim inhibits dihydrofolate reductase. Synergistic bactericidal activity. Used for UTIs, MRSA skin infections, PCP prophylaxis, and toxoplasmosis. TMP half-life ~10h, SMX ~10h. Both well absorbed orally (>90%).

Projected serum levels — 800 mg, twice daily

Trimethoprim/Sulfamethoxazole (Bactrim)
Trimethoprim/Sulfamethoxazole (Bactrim) modeled serum levels, 800 mg twice daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 1 days. 0 250 500 750 1k Day 0 Day 4 Day 7 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 1

Maintenance schedule: 800 mg twice daily (oral).

Modeled steady state after ~1 days: peak ≈ 593 mg, trough ≈ 106 mg body load. Population-based estimate over 15 days for a 800 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Antibiotic
Route modeled
Oral
Model confidence
inferred
Half-life
3.8 h
Common dose
800 mg
Suggested maximum
1.6k mg/day
Reference dose range
400–1.6k mg (single dose)
Suggested cadence
twice daily

Documented interactions

  • danger
    Candesartan + Trimethoprim/Sulfamethoxazole (Bactrim) CYP inhibition

    Trimethoprim/Sulfamethoxazole (Bactrim) reversible_inhibitor of CYP2C9 predicted to change Candesartan AUC by ~3.33x

  • danger
    Celecoxib (Celebrex) + Trimethoprim/Sulfamethoxazole (Bactrim) CYP inhibition

    Trimethoprim/Sulfamethoxazole (Bactrim) reversible_inhibitor of CYP2C9 predicted to change Celecoxib (Celebrex) AUC by ~2.97x

  • danger
    Glipizide (Glucotrol) + Trimethoprim/Sulfamethoxazole (Bactrim) CYP inhibition

    Trimethoprim/Sulfamethoxazole (Bactrim) reversible_inhibitor of CYP2C9 predicted to change Glipizide (Glucotrol) AUC by ~2.47x

  • danger
    Meloxicam (Mobic) + Trimethoprim/Sulfamethoxazole (Bactrim) CYP inhibition

    Trimethoprim/Sulfamethoxazole (Bactrim) reversible_inhibitor of CYP2C9 predicted to change Meloxicam (Mobic) AUC by ~2.20x

  • danger
    Phenytoin (Dilantin) + Trimethoprim/Sulfamethoxazole (Bactrim) CYP inhibition

    Trimethoprim/Sulfamethoxazole (Bactrim) reversible_inhibitor of CYP2C9 predicted to change Phenytoin (Dilantin) AUC by ~2.20x

  • danger
    Rifampin + Trimethoprim/Sulfamethoxazole (Bactrim) CYP induction

    Rifampin inducer of CYP2C9 predicted to change Trimethoprim/Sulfamethoxazole (Bactrim) AUC by ~0.45x

Serum checks 63 modeled interaction pairings for trimethoprim/sulfamethoxazole (bactrim) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Trimethoprim-sulfamethoxazole versus placebo for uncomplicated skin abscess (IDSA guidelines) Talan DA et al. · New England Journal of Medicine, 2016 DOI

    Large RCT (1265 patients) demonstrating TMP-SMX after incision and drainage of skin abscesses significantly increased cure rate (92% vs 86%) versus placebo, especially for MRSA infections.

  2. Clinical pharmacokinetics of co-trimoxazole (trimethoprim-sulfamethoxazole) Hoppu K et al. · Clinical Pharmacokinetics, 1987 DOI

    PK review establishing matched half-lives (~10 hours each), >90% oral bioavailability for both components, and optimal synergistic serum ratio of 1:20 (TMP:SMX) maintained by the 1:5 dosing ratio.

2 published studies referenced in the app, each with a plain-language summary.