SULFATRIM PEDIATRIC

Clinical safety rating: caution

Comprehensive clinical and safety monograph for SULFATRIM PEDIATRIC (SULFATRIM PEDIATRIC).

How it works

Sulfamethoxazole inhibits dihydropteroate synthase, blocking bacterial folic acid synthesis; trimethoprim inhibits dihydrofolate reductase, blocking reduction of dihydrofolate to tetrahydrofolate. Sequential blockade leads to bactericidal activity.

What the body does with it

Metabolism	Sulfamethoxazole is metabolized primarily by acetylation (N-acetyltransferase) and glucuronidation; trimethoprim undergoes O-demethylation, N-oxidation, and conjugation. Both are metabolized in the liver.
Excretion	Renal: 50-70% of total sulfamethoxazole (SMX) and 30-50% of total trimethoprim (TMP) are excreted unchanged in urine; the remainder as metabolites; biliary/fecal excretion is minimal.
Half-life	Sulfamethoxazole: 9-11 hours; Trimethoprim: 8-10 hours; prolonged in renal impairment (e.g., CrCl <30 mL/min).
Protein binding	Sulfamethoxazole: ~70% bound to albumin; Trimethoprim: ~44% bound to albumin.
Volume of Distribution	Sulfamethoxazole: Vd ~0.21 L/kg; Trimethoprim: Vd ~1.4 L/kg (higher tissue penetration).
Bioavailability	Oral: ~100% for both SMX and TMP.
Onset of Action	Oral: Therapeutic concentrations reached within 1-2 hours; clinical effect typically within 24-48 hours for susceptible infections.
Duration of Action	Duration of action: 12 hours (dosing interval); antibacterial effect persists for 24 hours after a single dose.

Classification & Brands

Dosing & administration

Sulfatrim Pediatric suspension contains sulfamethoxazole 200 mg and trimethoprim 40 mg per 5 mL. For patients >40 kg, dose is 800 mg SMX/160 mg TMP orally every 12 hours for 10-14 days.

Dosage form	SUSPENSION
Renal impairment	CrCl 15-30 mL/min: same dose but increase interval to every 24 hours. CrCl <15 mL/min: not recommended.
Liver impairment	Child-Pugh A: no adjustment. Child-Pugh B or C: use with caution, no specific dose guidelines; consider alternative therapy.
Pediatric use	Children >2 months: dose based on TMP component at 8 mg/kg/day divided every 12 hours (e.g., for 10 kg child: 80 mg TMP/day = 40 mg TMP every 12 hours, equivalent to 5 mL suspension every 12 hours). Maximum 160 mg TMP every 12 hours.
Geriatric use	Elderly may have reduced renal function; dose adjustment based on creatinine clearance (see renal_adjustment). Monitor for hypersensitivity and renal function. Avoid in those with folic acid deficiency.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for SULFATRIM PEDIATRIC (SULFATRIM PEDIATRIC).

Breastfeeding	Compatible with caution. Sulfamethoxazole and trimethoprim are excreted into breast milk. M/P ratio not well established; concentrations are low but may cause hemolysis in G6PD-deficient infants or interfere with folate metabolism. Avoid in premature or ill infants.
Teratogenic Risk	Pregnancy Category D. First trimester: Associated with increased risk of neural tube defects, cardiovascular malformations, and oral clefts due to folate antagonism. Second and third trimesters: Risk of kernicterus in the neonate due to bilirubin displacement from albumin; avoid use near term.

Warnings & precautions

■ FDA Black Box Warning

Fatal hypersensitivity reactions including Stevens-Johnson syndrome, toxic epidermal necrolysis, and hepatic necrosis; hemolytic anemia in G6PD deficiency; kernicterus in neonates; contraindicated in pregnancy at term and nursing mothers.

Side Effect Profile

Serious Effects

Absolute Contraindications

Hypersensitivity to sulfonamides or trimethoprim; marked hepatic damage; severe renal insufficiency without monitoring; megaloblastic anemia due to folate deficiency; pregnancy (especially near term); nursing mothers; neonates (especially premature) due to risk of kernicterus.

Clinical Precautions

Precautions

Monitor for severe skin reactions, hepatic injury, hematologic toxicity (including agranulocytosis, aplastic anemia), electrolyte disturbances (hyperkalemia with high-dose trimethoprim), hypersensitivity reactions, and photosensitivity. Use with caution in folate deficiency, impaired hepatic/renal function, and elderly.

Clinical Tips & Counseling

Drug interactions

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SULFATRIM PEDIATRIC

Clinical safety rating: caution

Comprehensive clinical and safety monograph for SULFATRIM PEDIATRIC (SULFATRIM PEDIATRIC).

How it works

What the body does with it

Metabolism	Sulfamethoxazole is metabolized primarily by acetylation (N-acetyltransferase) and glucuronidation; trimethoprim undergoes O-demethylation, N-oxidation, and conjugation. Both are metabolized in the liver.
Excretion	Renal: 50-70% of total sulfamethoxazole (SMX) and 30-50% of total trimethoprim (TMP) are excreted unchanged in urine; the remainder as metabolites; biliary/fecal excretion is minimal.
Half-life	Sulfamethoxazole: 9-11 hours; Trimethoprim: 8-10 hours; prolonged in renal impairment (e.g., CrCl <30 mL/min).
Protein binding	Sulfamethoxazole: ~70% bound to albumin; Trimethoprim: ~44% bound to albumin.
Volume of Distribution	Sulfamethoxazole: Vd ~0.21 L/kg; Trimethoprim: Vd ~1.4 L/kg (higher tissue penetration).
Bioavailability	Oral: ~100% for both SMX and TMP.
Onset of Action	Oral: Therapeutic concentrations reached within 1-2 hours; clinical effect typically within 24-48 hours for susceptible infections.
Duration of Action	Duration of action: 12 hours (dosing interval); antibacterial effect persists for 24 hours after a single dose.

Classification & Brands

Dosing & administration

Sulfatrim Pediatric suspension contains sulfamethoxazole 200 mg and trimethoprim 40 mg per 5 mL. For patients >40 kg, dose is 800 mg SMX/160 mg TMP orally every 12 hours for 10-14 days.

Dosage form	SUSPENSION
Renal impairment	CrCl 15-30 mL/min: same dose but increase interval to every 24 hours. CrCl <15 mL/min: not recommended.
Liver impairment	Child-Pugh A: no adjustment. Child-Pugh B or C: use with caution, no specific dose guidelines; consider alternative therapy.
Pediatric use	Children >2 months: dose based on TMP component at 8 mg/kg/day divided every 12 hours (e.g., for 10 kg child: 80 mg TMP/day = 40 mg TMP every 12 hours, equivalent to 5 mL suspension every 12 hours). Maximum 160 mg TMP every 12 hours.
Geriatric use	Elderly may have reduced renal function; dose adjustment based on creatinine clearance (see renal_adjustment). Monitor for hypersensitivity and renal function. Avoid in those with folic acid deficiency.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for SULFATRIM PEDIATRIC (SULFATRIM PEDIATRIC).

Breastfeeding	Compatible with caution. Sulfamethoxazole and trimethoprim are excreted into breast milk. M/P ratio not well established; concentrations are low but may cause hemolysis in G6PD-deficient infants or interfere with folate metabolism. Avoid in premature or ill infants.
Teratogenic Risk	Pregnancy Category D. First trimester: Associated with increased risk of neural tube defects, cardiovascular malformations, and oral clefts due to folate antagonism. Second and third trimesters: Risk of kernicterus in the neonate due to bilirubin displacement from albumin; avoid use near term.