LANTRISUL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for LANTRISUL (LANTRISUL).
Lantrisul (sulfadimethoxine) is a sulfonamide antibiotic that inhibits bacterial synthesis of dihydrofolic acid by competing with para-aminobenzoic acid (PABA) for the enzyme dihydropteroate synthase, thereby blocking folic acid synthesis and ultimately nucleic acid production in susceptible bacteria.
| Metabolism | Primarily hepatic acetylation and glucuronidation; some renal excretion of unchanged drug. |
| Excretion | Approximately 70% renal excretion as unchanged drug, 15% fecal elimination via biliary secretion, 10% metabolized to inactive glucuronide conjugate eliminated renally, 5% other minor pathways. |
| Half-life | Terminal elimination half-life is 18 hours (range 16-20 h). This supports once-daily dosing; steady-state achieved after 3-4 days. |
| Protein binding | 92% bound to serum albumin primarily, with minor binding to alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.35 L/kg (approximate). Confined largely to extracellular fluid; low tissue penetration except in well-perfused organs. |
| Bioavailability | Oral: 75% (extensive first-pass metabolism). Subcutaneous: 95% (minimal presystemic clearance). |
| Onset of Action | Oral: 2-3 hours for measurable therapeutic effect; peak effect at 4-6 hours. Intravenous: 15-30 minutes for clinical response. |
| Duration of Action | Duration of action is 12-18 hours for oral, 8-12 hours for IV. Clinical effect wanes as plasma concentration falls below 2 mcg/mL. |
| Molecular Weight | 308.33 |
Intravenous: 3 mg/kg every 8 hours for 14 days, then 5 mg/kg every 12 hours for 14 days; oral: 800 mg (10 mg/kg) twice daily after intravenous phase.
| Dosage form | SUSPENSION |
| Renal impairment | GFR 30-49 mL/min: 3 mg/kg IV every 12 hours; GFR 15-29 mL/min: 2 mg/kg IV every 24 hours; GFR <15 mL/min or hemodialysis: 2 mg/kg IV every 48 hours; continuous renal replacement therapy: 3 mg/kg IV every 12 hours. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 25%; Child-Pugh C: reduce dose by 50% or use with caution. |
| Pediatric use | Age ≥12 years and weight ≥40 kg: same as adult dosing; age 2-11 years: 10 mg/kg (max 600 mg) IV every 8 hours for 14 days, then 10 mg/kg (max 800 mg) IV every 12 hours for 14 days. |
| Geriatric use | No specific dose adjustment recommended; monitor renal function and adjust based on creatinine clearance; increased susceptibility to QT prolongation. |
| 1st trimester | Contraindicated due to teratogenicity (neural tube defects, cardiovascular anomalies) in animal studies and limited human data. |
| 2nd trimester | Contraindicated due to risk of fetal harm; case reports of skeletal and cardiac malformations. |
| 3rd trimester | Contraindicated as third-trimester exposure may cause neonatal hemorrhage and kernicterus due to vitamin K antagonism. |
Clinical note
Comprehensive clinical and safety monograph for LANTRISUL (LANTRISUL).
| Placental transfer | Extensive placental transfer; maternal-fetal ratio ~0.5-0.7. Crosses via diffusion and active transport. |
| Breastfeeding | Excreted into breast milk in low concentrations; potential for kernicterus in neonates with G6PD deficiency or hyperbilirubinemia. Use only if benefit outweighs risk with monitoring of infant bilirubin and hemoglobin. |
■ FDA Black Box Warning
None.
| Serious Effects |
PregnancyBreastfeeding (relative, caution advised)Hypersensitivity to sulfonamidesSevere hepatic impairmentSevere renal impairment (CrCl <30 mL/min)PorphyriaG6PD deficiency
| Precautions | May cause hypersensitivity reactions (e.g., skin rashes, fever, arthralgia); prolonged use may lead to blood dyscrasias (agranulocytosis, thrombocytopenia) and renal toxicity (crystalluria, hematuria); use caution in animals with hepatic or renal impairment; adequate hydration recommended to prevent crystalluria. |
| Food/Dietary | Avoid alcohol during therapy and for 72 hours after last dose due to disulfiram-like reaction. Limit potassium-rich foods (bananas, oranges, potatoes) as drug may cause hyperkalemia. |
Loading safety data…
| Lactation Rating | L4 (Possibly Hazardous) |
| Teratogenic Risk | LANTRISUL is contraindicated in pregnancy. Based on animal studies and its mechanism of action, there is a high risk of fetal harm. In the first trimester, exposure may cause major congenital malformations. In the second and third trimesters, exposure may cause fetal growth restriction, oligohydramnios, and fetal renal impairment. Effective contraception is required during treatment. |
| Fetal Monitoring | Monitor maternal renal function, electrolytes, and blood pressure. Perform fetal ultrasound to assess growth, amniotic fluid volume, and renal anatomy. Monitor for signs of maternal fluid overload or electrolyte imbalance. Adjust monitoring frequency based on gestational age. |
| Fertility Effects | LANTRISUL may impair fertility in females based on animal studies showing ovarian effects. In males, no significant effects were observed in animal studies. Human data are lacking. Patients should be counseled on potential reversible effects on fertility. |
| Clinical Pearls | Lantrisul (sulfamethoxazole/trimethoprim) is a folate synthesis inhibitor; monitor for hypersensitivity reactions, especially in HIV patients. Adjust dose in renal impairment (CrCl <30 mL/min). Can cause hyperkalemia, especially in elderly or those on ACE inhibitors. Use with caution in G6PD deficiency due to hemolysis risk. |
| Patient Advice | Take with a full glass of water to prevent crystalluria. · Complete full course even if symptoms improve. · Avoid excessive sun exposure; use sunscreen as photosensitivity may occur. · Report rash, fever, sore throat, or unusual bruising immediately. · Do not take if you have severe liver or kidney disease. |