Trimethoprim-Sulfamethoxazole DS


  • Type: Sulfonamide
  • Dosage Forms: 160/800; 40mg TMP/5mL
  • Common Trade Names: Bactrim DS
  • Abbreviations: TMP-SMX, TMP-SMZ

Adult Dosing


1 tab (160mg TMP) PO Q12h

PCP Prophylaxis

80-160mg TMP PO daily

PCP Treatment

15-20mg/kg/day TMP PO divided q6-8h x 21 days

Pediatric Dosing

General (>2mo)

  • Mild-mod infection
    • 4-5mg/kg TMP PO q12hr
  • Severe infection
    • 15-20mg/kg/dy TMP PO divided q6-8h

Special Populations

  • Pregnancy: D
  • Lactation: ?
  • Renal (Adult & Pediatric)
    • CrCl 15-30: Decrease dose by 50%
    • CrCl <15: Avoid use
    • Hemodialysis: Give supplement
    • Peritoneal Dialysis: No supplement
  • Hepatic (Adult & Pediatric)[1]
    • Mild-mod impairment: Caution advised
    • Significant impairment: Contraindicated


  • Allergy to class/drug
  • <2 months of age (except as PCP prophylaxis)
  • Significant hepatic impairment
  • Megaloblastic anemia or folate deficiency
  • G6PD deficiency

Adverse Reactions




  • Half-life: 6-12h (20-50h ESRD)
  • Metabolism:
    • Hepatic
  • Excretion:
    • Urine - both as unchanged drug and metabolites
  • Mechanism of Action: Bactericidal via interfering with folic acid synthesis

Antibiotic Sensitivities[2]

Group Organism Sensitivity
Gram PositiveStrep. Group A, B, C, GX22
Strep. PneumoniaeS
Viridans strepX1
Strep. anginosus gpX1
Enterococcus faecalisX22
Enterococcus faeciumR
Staph. EpidermidisI
C. jeikeiumR
L. monocytogenesS
Gram NegativesN. gonorrhoeaeI
N. meningitidisX2
Moraxella catarrhalisS
H. influenzaeI
E. coliI
Klebsiella spI
E. coli/Klebsiella ESBL+I
E coli/Klebsiella KPC+R
Enterobacter sp, AmpC negX1
Enterobacter sp, AmpC posX1
Serratia spX1
Serratia marcescensI
Salmonella spI
Shigella spI
Proteus mirabilisS[3]
Proteus vulgarisS[4]
Providencia sp.X1
Morganella sp.X1
Citrobacter freundiiX1
Citrobacter diversusX1
Citrobacter sp.X1
Aeromonas spX1
Acinetobacter sp.I
Pseudomonas aeruginosaR
Burkholderia cepaciaS
Stenotrophomonas maltophiliaS
Yersinia enterocoliticaS
Francisella tularensisS
Brucella sp.X2
Legionella sp.S
Pasteurella multocidaX1
Haemophilus ducreyiI
Vibrio vulnificusX1
MiscChlamydophila spX1
Mycoplasm pneumoniaeX1
Rickettsia spX1
Mycobacterium aviumX1
Bacteroides fragilisR
Prevotella melaninogenicaX1
Clostridium difficileX1
Clostridium (not difficile)X1
Fusobacterium necrophorumX1
Peptostreptococcus sp.X1


  • S susceptible/sensitive (usually)
  • I intermediate (variably susceptible/resistant)
  • R resistant (or not effective clinically)
  • S+ synergistic with cell wall antibiotics
  • U sensitive for UTI only (non systemic infection)
  • X1 no data
  • X2 active in vitro, but not used clinically
  • X3 active in vitro, but not clinically effective for Group A strep pharyngitis or infections due to E. faecalis
  • X4 active in vitro, but not clinically effective for strep pneumonia

See Also


  1. Trimethoprim-sulfamethoxazole (co-trimoxazole): Drug information. UpToDate. Accessed April 2, 2019.
  2. Sanford Guide to Antimicrobial Therapy 2014
  3. GlobalRPH. Bactrim. Last revised 10/2009.
  4. GlobalRPH. Bactrim. Last revised 10/2009.
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