THIOSULFIL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for THIOSULFIL (THIOSULFIL).
Thiosulfil (sulfamethizole) is a sulfonamide antibiotic that inhibits bacterial dihydropteroate synthase, blocking folic acid synthesis and thereby nucleic acid production.
| Metabolism | Primarily hepatic metabolism via acetylation and glucuronidation; excreted renally as unchanged drug and metabolites. |
| Excretion | Renal: 70-90% as unchanged drug via glomerular filtration and tubular secretion. Biliary/fecal: <5%. |
| Half-life | Terminal elimination half-life is 2-4 hours in patients with normal renal function (creatinine clearance >80 mL/min); prolonged to 20-50 hours in severe renal impairment (CrCl <30 mL/min). |
| Protein binding | 85-90% bound to serum albumin. |
| Volume of Distribution | 0.2-0.4 L/kg, indicating distribution primarily in extracellular fluid and low tissue penetration. |
| Bioavailability | Oral: 85-95% (well absorbed from gastrointestinal tract). |
| Onset of Action | Oral: 2-4 hours for therapeutic urinary concentrations. |
| Duration of Action | 12-24 hours based on urinary concentrations above MIC for susceptible organisms; requires q6-8h dosing for sustained effect. |
500 mg orally twice daily for 10-14 days.
| Dosage form | TABLET |
| Renal impairment | GFR 30-50 mL/min: 500 mg every 24-36 hours; GFR 10-29 mL/min: 500 mg every 36-48 hours; GFR <10 mL/min: 500 mg every 48-72 hours or consider alternative. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: 250 mg orally twice daily; Child-Pugh C: not recommended. |
| Pediatric use | For children >2 months: 25-50 mg/kg/day orally divided every 12 hours; maximum 4 g/day. For infants <2 months: not recommended. |
| Geriatric use | Start at 250 mg orally twice daily; increase to 500 mg twice daily based on tolerance and renal function; monitor for hypersensitivity and renal impairment. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for THIOSULFIL (THIOSULFIL).
| Breastfeeding | Excreted in breast milk in low amounts. M/P ratio not established. Caution in infants with hyperbilirubinemia or G6PD deficiency. American Academy of Pediatrics considers compatible with breastfeeding. |
| Teratogenic Risk | Pregnancy category D. Sulfonamides cross the placenta and may cause kernicterus in the newborn if used near term. Avoid use in first and third trimesters; second trimester use only if clearly needed. |
| Fetal Monitoring |
■ FDA Black Box Warning
Sulfonamides have been associated with severe hypersensitivity reactions including Stevens-Johnson syndrome, toxic epidermal necrolysis, and hematologic toxicities. Use caution in patients with history of sulfonamide allergy.
| Serious Effects |
Hypersensitivity to sulfonamides, severe renal or hepatic impairment, porphyria, pregnancy (especially near term), and lactation.
| Precautions | Monitor for hypersensitivity reactions, hematologic effects (agranulocytosis, aplastic anemia), renal toxicity, and photosensitivity. Use cautiously in patients with renal impairment or G6PD deficiency. |
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| Monitor maternal complete blood count, renal function, and bilirubin levels. Fetal monitoring for jaundice and kernicterus if maternal use near term. Assess for hypersensitivity reactions. |
| Fertility Effects | No known adverse effects on fertility in humans. Animal studies show no impairment. |