Trimethoprim-Sulfamethoxazole DS

General

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

Adult Dosing

General

• 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)
  • Mild-mod impairment: Caution advised
  • Significant impairment: Contraindicated

Contraindications

• 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

Serious

• Stevens-Johnson Syndrome
• Toxic Epidermal Necrolysis
• Fulminant hepatic necrosis
• Agranulocytosis
• Aplastic anemia
• Blood dyscrasias
• Thrombocytopenia
• Hypersensitivity Reaction
• Photosensitivity
• Hepatotoxicity
• Pancreatitis
• Intersitial nephritis
• Renal Failure
• Pulmonary infiltrates
• Myelosuppression
• Methemoglobinemia
• Hyperkalemia
• Hyponatremia
• Aseptic meningitis
• Seizures
• Lupus Erythematosus
• Hypoglycemia
• Clostridium difficile
• Rhabdomyolysis
• Congenital malformations
• Congenital neural tube defects
• Kernicterus (neonates)

Common

• Nausea and Vomiting
• Anorexia
• Rash
• Urticaria
• Hypersensitivity Reaction
• Photosensitivity
• Diarrhea
• Dizziness
• Dyspepsia
• Headache
• Lethargy

Pharmacology

• 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

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
	MSSA	S
	MRSA	S
	CA-MRSA	S
	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
	Proteus vulgaris	S
	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

Key

• 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

Comments

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

• Antibiotics (Main)