Trimethoprim-Sulfamethoxazole DS

(Redirected from TMP-SMX 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
  • Pregnancy (class D)

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 Positive Strep. Group A, B, C, G X22
Strep. Pneumoniae S
Viridans strep X1
Strep. anginosus gp X1
Enterococcus faecalis X22
Enterococcus faecium R
Staph. Epidermidis I
C. jeikeium R
L. monocytogenes S
Gram Negatives N. gonorrhoeae I
N. meningitidis X2
Moraxella catarrhalis S
H. influenzae I
E. coli I
Klebsiella sp I
E. coli/Klebsiella ESBL+ I
E coli/Klebsiella KPC+ R
Enterobacter sp, AmpC neg X1
Enterobacter sp, AmpC pos X1
Serratia sp X1
Serratia marcescens I
Salmonella sp I
Shigella sp I
Proteus mirabilis S[3]
Proteus vulgaris S[4]
Providencia sp. X1
Morganella sp. X1
Citrobacter freundii X1
Citrobacter diversus X1
Citrobacter sp. X1
Aeromonas sp X1
Acinetobacter sp. I
Pseudomonas aeruginosa R
Burkholderia cepacia S
Stenotrophomonas maltophilia S
Yersinia enterocolitica S
Francisella tularensis S
Brucella sp. X2
Legionella sp. S
Pasteurella multocida X1
Haemophilus ducreyi I
Vibrio vulnificus X1
Misc Chlamydophila sp X1
Mycoplasm pneumoniae X1
Rickettsia sp X1
Mycobacterium avium X1
Anaerobes Actinomyces X1
Bacteroides fragilis R
Prevotella melaninogenica X1
Clostridium difficile X1
Clostridium (not difficile) X1
Fusobacterium necrophorum X1
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


Bactrim dosing is based on the trimethoprim part not the sulfamethoxazole part.

  • The dosing in 8-10mg/kg of trimethoprim divided q12 hours (4-5 mg/kg per dose).
  • The concentration of Bactrim is 200 mg of sulfamethoxazole and 40 mg of trimethoprim in 5 mL.
  • Example: 10 kg child - 8mg/kg per day of trimethoprim part which is 80 mg per day. Divide by 2 = 40 mg of trimethoprim per dose. Based on the above concentration patient will get 5 mL of Bactrim 2 times per day.

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.