SULMEPRIM PEDIATRIC
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SULMEPRIM PEDIATRIC (SULMEPRIM PEDIATRIC).
Sulfamethoxazole inhibits bacterial dihydropteroate synthase, blocking folate synthesis; trimethoprim inhibits bacterial dihydrofolate reductase, blocking folate reduction; sequential blockade leads to bactericidal effect.
| Metabolism | Sulfamethoxazole undergoes acetylation and glucuronidation; trimethoprim undergoes oxidation (CYP3A4) and glucuronidation. Both are primarily renally excreted. |
| Excretion | Renal excretion accounts for approximately 70% (as unchanged sulfamethoxazole and trimethoprim) and 20% as metabolites; biliary/fecal elimination is minor at <10%. |
| Half-life | Terminal elimination half-life: Sulfamethoxazole 9–12 hours, Trimethoprim 8–11 hours; prolonged in renal impairment (creatinine clearance <15 mL/min) requiring dose adjustment. |
| Protein binding | Sulfamethoxazole: ~70% bound primarily to albumin; Trimethoprim: ~44% bound to albumin. |
| Volume of Distribution | Sulfamethoxazole: 0.21–0.36 L/kg; Trimethoprim: 1.3–1.8 L/kg. Indicates extensive tissue distribution for trimethoprim, including CSF, lungs, and kidneys. |
| Bioavailability | Oral: ≥90% for both components; well absorbed from gastrointestinal tract. |
| Onset of Action | Oral: Therapeutic effect typically within 24–48 hours; intravenous: within 6–12 hours for systemic infections. |
| Duration of Action | Duration 12 hours; dosing interval commonly every 12 hours. Clinical effect persists as long as drug levels exceed MIC; typically 2–3 days after last dose for susceptible organisms. |
| Molecular Weight | Sulfamethoxazole: 253.28 Da; Trimethoprim: 290.3 Da |
For Pneumocystis jirovecii pneumonia (PCP): 15-20 mg/kg/day (based on trimethoprim component) intravenously divided every 6-8 hours for 14-21 days. For other infections: 8-10 mg/kg/day (trimethoprim) orally or intravenously divided every 12 hours.
| Dosage form | SUSPENSION |
| Renal impairment | CrCl 15-30 mL/min: reduce dose by 50% and increase interval to every 12 hours. CrCl <15 mL/min: use only with therapeutic drug monitoring and extended intervals (e.g., every 24-48 hours); consider alternative. Hemodialysis: administer after dialysis. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50% and monitor. Child-Pugh C: avoid use due to risk of hepatotoxicity and accumulation. |
| Pediatric use | For PCP: 15-20 mg/kg/day (trimethoprim) intravenously divided every 6 hours for 21 days. For UTI: 6-12 mg/kg/day (trimethoprim) orally divided every 12 hours for 10 days. Maximum daily dose (trimethoprim): 20 mg/kg/day. |
| Geriatric use | Monitor renal function closely; adjust dose based on CrCl (see renal adjustment). Avoid use if sulfonamide allergy. Increased risk of hyperkalemia with high doses; monitor serum potassium. Use with caution in patients with folate deficiency. |
| 1st trimester | Avoid due to potential teratogenicity; sulfonamides have been associated with cleft palate and other malformations in animal studies. Use only if benefit outweighs risk. |
| 2nd trimester | Caution; may increase risk of kernicterus in neonates if used near term, but risk is lower in 2nd trimester. Use only if clearly needed. |
| 3rd trimester | Avoid near term; sulfonamides displace bilirubin from albumin, increasing risk of kernicterus. Contraindicated after 38 weeks gestation. |
Clinical note
Comprehensive clinical and safety monograph for SULMEPRIM PEDIATRIC (SULMEPRIM PEDIATRIC).
| Placental transfer | Both sulfamethoxazole and trimethoprim cross the placenta; trimethoprim reaches fetal concentrations similar to maternal serum. Sulfamethoxazole levels in cord blood are about 50% of maternal levels. |
| Breastfeeding | Sulfamethoxazole and trimethoprim are excreted into breast milk in small amounts. Risk of kernicterus in nursing infants is low if infant is healthy and full-term, but avoid in premature infants, those with hyperbilirubinemia, or G6PD deficiency. Monitor infant for jaundice and diarrhea. |
■ FDA Black Box Warning
Fatal hypersensitivity reactions including Stevens-Johnson syndrome, toxic epidermal necrolysis, and hepatic necrosis have been reported. Co-administration with leucovorin in Pneumocystis jirovecii pneumonia may increase mortality.
| Serious Effects |
Hypersensitivity to sulfonamides, trimethoprim, or any componentMegaloblastic anemia due to folate deficiencySevere hepatic or renal impairment (CrCl <15 mL/min)PorphyriaConcurrent use with dofetilide (increased risk of cardiotoxicity)Infants <2 months of age (risk of kernicterus)
| Precautions | Monitor for hypersensitivity reactions (rash, fever, arthralgia) and discontinue immediately, Risk of hemolytic anemia in G6PD-deficient patients, Risk of kernicterus in neonates with hyperbilirubinemia; avoid in infants <2 months, Risk of hyperkalemia due to trimethoprim's potassium-sparing diuretic effect, Risk of hypoglycemia, especially in renal impairment or with concurrent sulfonylureas, Adequate fluid intake to prevent crystalluria and stone formation, Hematologic monitoring (CBC) for megaloblastic anemia, granulocytopenia, or thrombocytopenia, Use cautiously in elderly patients, those with folate deficiency, or renal/hepatic impairment |
| Food/Dietary |
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| Lactation Rating | L2 (Limited data - probably compatible) / Safe |
| Teratogenic Risk | First trimester: Folate antagonist effect increases risk of neural tube defects; contraindicated unless benefit outweighs risk. Second/third trimesters: Risk of kernicterus in neonates due to bilirubin displacement from albumin; avoid near term. |
| Fetal Monitoring | Monitor for hemolysis in G6PD-deficient patients; complete blood counts, renal function; fetal ultrasound for neural tube defects if exposure in first trimester. |
| Fertility Effects | No established effects on fertility in humans. May reduce folate levels, potentially impacting oocyte quality; folate supplementation recommended. |
| Avoid alcohol during therapy and for 72 hours after last dose (disulfiram-like reaction). Limit intake of potassium-rich foods (e.g., bananas, oranges) in patients with renal impairment, as trimethoprim can elevate serum potassium. |
| Clinical Pearls | Sulmeprim Pediatric (trimethoprim-sulfamethoxazole) is a fixed-dose combination used for pediatric infections. Adjust dose based on renal function; contraindicated in infants <2 months due to kernicterus risk. Monitor for hypersensitivity reactions, especially in HIV patients. Administer with plenty of fluids to prevent crystalluria. Avoid in G6PD deficiency due to hemolysis risk. May potentiate warfarin and hypoglycemic agents. |
| Patient Advice | Take exactly as prescribed; complete full course even if feeling better. · Drink plenty of fluids to prevent kidney stones. · Avoid prolonged sun exposure; use sunscreen as photosensitivity may occur. · Report any rash, sore throat, fever, or unusual bleeding immediately. · Do not use if allergic to sulfa drugs or trimethoprim. · Inform doctor if taking blood thinners or diabetes medications. |