SULLA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SULLA (SULLA).
SULLA (sulfamethoxazole/trimethoprim) inhibits bacterial dihydropteroate synthase and dihydrofolate reductase, sequentially blocking folate synthesis and thereby nucleic acid production.
| Metabolism | Sulfamethoxazole is primarily metabolized via N4-acetylation; trimethoprim undergoes hepatic metabolism via demethylation and oxidation. Both are eliminated renally. |
| Excretion | Renal: 70-90% unchanged; biliary/fecal: 5-10% |
| Half-life | 6-12 hours; prolonged in renal impairment (up to 30 hours) |
| Protein binding | 80% bound to albumin |
| Volume of Distribution | 2-3 L/kg; large distribution suggests extravascular penetration |
| Bioavailability | Oral: 100% (well absorbed) |
| Onset of Action | Oral: 2-4 hours; Intravenous: 5-15 minutes |
| Duration of Action | 6-12 hours; may extend in renal dysfunction |
| Molecular Weight | 250.3 |
100 mg orally once daily, increased to 200 mg daily if needed.
| Dosage form | TABLET |
| Renal impairment | GFR 30-60 mL/min: 100 mg every 48 hours. GFR <30 mL/min: 100 mg twice weekly. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B or C: use with caution, dose reduction by 50%. |
| Pediatric use | Not established in patients <18 years. |
| Geriatric use | Start at 100 mg daily; monitor renal function. |
| 1st trimester | Avoid. Linked to neural tube defects and cardiovascular malformations. Sulfonamides may increase risk of kernicterus. |
| 2nd trimester | Use only if clearly needed. Risk of hemolytic anemia in G6PD-deficient fetus. |
| 3rd trimester | Contraindicated near term due to risk of kernicterus in newborn. |
Clinical note
Comprehensive clinical and safety monograph for SULLA (SULLA).
| Placental transfer | Crosses placenta readily; fetal serum concentrations 50-100% of maternal levels. |
| Breastfeeding | Compatible with breastfeeding for most healthy term infants; however, use caution in preterm, ill, or hyperbilirubinemic infants, or those with G6PD deficiency. Monitor for jaundice and hemolysis. |
| Lactation Rating |
■ FDA Black Box Warning
Fatalities associated with sulfonamide hypersensitivity reactions including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias. Avoid use in patients with a history of sulfonamide allergy.
| Serious Effects |
Known hypersensitivity to sulfonamidesPorphyriaInfants <2 months of age (unless for congenital toxoplasmosis)Near term pregnancy (risk of kernicterus)
| Precautions | Hypersensitivity reactions, severe cutaneous adverse reactions (SCAR), hematologic toxicity, hepatic necrosis, renal impairment (dose adjustment), folate deficiency, hyperkalemia (especially in elderly), hypoglycemia, photosensitivity. |
| Food/Dietary | Avoid acidic foods or beverages (e.g., citrus, cola) as they may increase crystalluria risk. No significant food interactions beyond hydration. |
Loading safety data…
| L2 (Safer) |
| Teratogenic Risk | SULLA (sulfadiazine) is a sulfonamide antibiotic. First trimester: Limited data, but sulfonamides are generally avoided due to potential teratogenicity (e.g., cleft palate in animal studies); risk cannot be excluded. Second and third trimesters: Risk of kernicterus in neonates if administered near term due to displacement of bilirubin from albumin; avoid use after 32 weeks gestation. Overall, FDA Pregnancy Category C. |
| Fetal Monitoring | Maternal: Complete blood count, renal function, liver function tests, and urinalysis due to risk of hematologic toxicity (agranulocytosis, hemolytic anemia) and crystalluria; monitor for hypersensitivity reactions (Stevens-Johnson syndrome). Fetal: Ultrasound for growth and potential anomalies if administered in first trimester; assess for jaundice or signs of kernicterus if used near term. |
| Fertility Effects | No significant impact on fertility reported in human or animal studies. Sulfonamides are not known to adversely affect spermatogenesis or oogenesis. |
| Clinical Pearls | SULLA (sulfadimethoxine) is a long-acting sulfonamide; ensure adequate hydration to prevent crystalluria. Monitor for hypersensitivity reactions, especially in patients with sulfa allergy. Not effective against rickettsiae; avoid in severe renal impairment. |
| Patient Advice | Take with a full glass of water and maintain adequate fluid intake to prevent kidney stones. · Complete the full course even if symptoms improve. · Avoid prolonged sun exposure; use sunscreen as photosensitivity may occur. · Report any skin rash, sore throat, fever, or unusual bleeding immediately. · Do not take if you have a known sulfa allergy. |