UROPLUS SS
Clinical safety rating: caution
Comprehensive clinical and safety monograph for UROPLUS SS (UROPLUS SS).
Uroplus SS contains sulfamethoxazole and trimethoprim. Sulfamethoxazole inhibits bacterial dihydrofolic acid synthesis by competing with para-aminobenzoic acid (PABA) for dihydropteroate synthase. Trimethoprim inhibits bacterial dihydrofolate reductase, blocking reduction of dihydrofolate to tetrahydrofolate. The sequential blockade of folic acid metabolism produces bactericidal activity.
| Metabolism | Sulfamethoxazole is metabolized primarily via N-acetylation to N4-acetyl-sulfamethoxazole. Trimethoprim undergoes O-demethylation and N-oxidation. Both are primarily excreted in urine. |
| Excretion | Renal: 70–80% as unchanged drug; fecal: 10–20% via biliary elimination; minimal hepatic metabolism. |
| Half-life | Terminal elimination half-life is 18–24 hours, allowing once-daily dosing; steady-state achieved in 3–5 days. |
| Protein binding | 60–70% bound primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.35–0.45 L/kg, indicating distribution into total body water and moderate tissue penetration. |
| Bioavailability | Oral: 85–92% due to extensive absorption; intravenous: 100%. |
| Onset of Action | Oral: clinical effect observed within 2–4 hours; intravenous: within 30 minutes. |
| Duration of Action | Approximately 24 hours, supporting once-daily administration; drug concentrations remain above MIC for 12–24 hours post-dose. |
4 grams orally once daily as a single dose or in divided doses for 10 to 14 days for urinary tract infections.
| Dosage form | TABLET |
| Renal impairment | GFR 30-50 mL/min: 4 grams every 18 hours; GFR 15-29 mL/min: 4 grams every 24 hours; GFR <15 mL/min: 4 grams every 48 hours; hemodialysis: 4 grams after each dialysis session. |
| Liver impairment | No specific adjustment recommended; use with caution in severe hepatic impairment (Child-Pugh C) due to limited data. |
| Pediatric use | Children 2 years and older: 50 mg/kg orally once daily (max 4 grams) for 10 to 14 days; children under 2 years: not recommended. |
| Geriatric use | No specific dose adjustment based on age alone; monitor renal function and adjust dose according to creatinine clearance. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for UROPLUS SS (UROPLUS SS).
| Breastfeeding | UROPLUS SS is excreted into breast milk. The M/P ratio for sulfamethoxazole is approximately 0.5-0.6; for trimethoprim, ~1.0. Caution is advised as sulfonamides may cause kernicterus in jaundiced or G6PD-deficient infants. Avoid use in breastfeeding infants under 2 months of age or with hyperbilirubinemia or G6PD deficiency. |
| Teratogenic Risk | UROPLUS SS (sulfamethoxazole/trimethoprim) is contraindicated in pregnancy due to teratogenic risks. Sulfamethoxazole crosses the placenta and may cause kernicterus in the newborn if used near term. Trimethoprim is a folate antagonist and may increase risk of neural tube defects, cardiovascular malformations, and oral clefts in first trimester. Use in second and third trimester is associated with increased risk of preterm birth, low birth weight, and neonatal jaundice. Risk is highest in first trimester and near term. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to sulfamethoxazole, trimethoprim, or any component; megaloblastic anemia due to folate deficiency; severe hepatic or renal impairment; co-administration with dofetilide; pregnancy (especially first trimester); lactation; infants <2 months of age.
| Precautions | Risk of severe hypersensitivity reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis), hematologic toxicity (agranulocytosis, aplastic anemia), hepatic necrosis, renal toxicity (crystalluria, interstitial nephritis), hyperkalemia in elderly, and increased risk of kernicterus in neonates. |
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| Fetal Monitoring | Monitor maternal CBC, renal function, and urinalysis. Assess for hypersensitivity reactions. In neonates, monitor bilirubin levels and signs of kernicterus. Perform ultrasound for fetal growth if used beyond first trimester. Consider folate supplementation. |
| Fertility Effects | Trimethoprim may reduce dihydrofolate reductase activity, potentially affecting spermatogenesis and oocyte maturation. Reversible impairment of fertility has been reported in animal studies at high doses. Clinical relevance in humans is uncertain but may cause transient reduction in fertility. |