SULFATRIM PEDIATRIC
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SULFATRIM PEDIATRIC (SULFATRIM PEDIATRIC).
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.
| 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. |
| Molecular Weight | Sulfamethoxazole: 253.28 Da; Trimethoprim: 290.32 Da |
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. |
| 1st trimester | Avoid; associated with increased risk of congenital malformations (neural tube defects, cardiovascular) due to folate antagonism. Use only if no alternative and benefit outweighs risk. |
| 2nd trimester | Avoid; risk of kernicterus and hemolytic anemia in fetus due to displacement of bilirubin from albumin and folate antagonism. Clotrimazole is preferred for candida infections. |
| 3rd trimester | Contraindicated; high risk of kernicterus in neonate, hemolytic anemia, and methemoglobinemia. Sulfamethoxazole crosses placenta and displaces bilirubin. |
Clinical note
Comprehensive clinical and safety monograph for SULFATRIM PEDIATRIC (SULFATRIM PEDIATRIC).
| Placental transfer | Both sulfamethoxazole and trimethoprim cross the placenta; sulfamethoxazole achieves fetal serum concentrations 50-90% of maternal levels, trimethoprim ~30-60%. Extensive placental transfer. |
| Breastfeeding | Sulfamethoxazole is excreted into breast milk in low concentrations; trimethoprim is also excreted. Potential for hemolytic anemia in G6PD-deficient infants, kernicterus in jaundiced or premature infants, and interference with folate metabolism. American Academy of Pediatrics considers compatible with breastfeeding, but caution in G6PD deficiency, ill or premature infants. Avoid in infants with hyperbilirubinemia or G6PD deficiency. |
■ 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.
| Serious Effects |
Hypersensitivity to sulfonamides, trimethoprim, or any componentMegaloblastic anemia due to folate deficiencyInfants less than 2 months of age (except for treatment of congenital toxoplasmosis)Severe hepatic or renal impairment (CrCl <15 mL/min) unless monitoredPorphyria (may precipitate acute attack)G6PD deficiency (risk of hemolytic anemia)
| 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. |
| Food/Dietary | Avoid potassium-rich foods (e.g., bananas, oranges, potatoes) and high-potassium salt substitutes as trimethoprim can increase serum potassium. Alcohol may cause disulfiram-like reaction (rare). |
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| Lactation Rating | L3 (Moderately Safe) / Caution |
| 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. |
| Fetal Monitoring | Complete blood count, renal function, and liver function tests. Ultrasound for fetal growth and development if used in first trimester. Monitor neonate for jaundice and kernicterus if used near term. |
| Fertility Effects | No known significant impact on fertility. Folate antagonism may theoretically affect gametogenesis, but clinical significance is unclear. |
| Clinical Pearls | SULFATRIM PEDIATRIC contains sulfamethoxazole and trimethoprim (co-trimoxazole). Use with caution in infants <2 months due to risk of kernicterus from sulfonamide displacement of bilirubin. Monitor for hypersensitivity reactions (Stevens-Johnson syndrome). Adjust dose in renal impairment (CrCl <30 mL/min contraindicated). Avoid in G6PD deficiency due to hemolytic anemia risk. Ensure adequate hydration to prevent crystalluria. |
| Patient Advice | Take with a full glass of water and stay well-hydrated to prevent kidney stones. · Complete the full course even if symptoms improve. · Avoid prolonged sun exposure; use sunscreen as this drug increases photosensitivity. · Report any rash, sore throat, fever, or unusual bleeding immediately. · Shake suspension well before measuring dose. |