SOXAZOLE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SOXAZOLE (SOXAZOLE).
Soxazole is a synthetic antibacterial agent that inhibits bacterial dihydropteroate synthase, blocking folate synthesis and thereby interfering with nucleic acid production.
| Metabolism | Primarily metabolized by hepatic acetylation and glucuronidation; metabolites excreted renally. |
| Excretion | Renal excretion of unchanged drug (70-80%) and hepatic metabolism with fecal elimination (15-20%); biliary excretion accounts for minor route (<5%). |
| Half-life | Terminal elimination half-life is 8-12 hours in adults; prolonged to 15-20 hours in renal impairment (CrCl <30 mL/min). |
| Protein binding | 92-96% bound to albumin. |
| Volume of Distribution | 0.3-0.5 L/kg, indicating distribution primarily in extracellular fluid. |
| Bioavailability | Oral: 80-90% (well absorbed); IV: 100%. |
| Onset of Action | Oral: 1-2 hours; IV: Immediate (within minutes). |
| Duration of Action | Oral: 8-12 hours; IV: 6-8 hours. Duration is dose-dependent and extended in renal impairment. |
| Molecular Weight | 267.31 |
500 mg orally every 6 hours for 7-14 days.
| Dosage form | TABLET |
| Renal impairment | GFR 30-50 mL/min: 250 mg every 6 hours; GFR 10-29 mL/min: 250 mg every 12 hours; GFR <10 mL/min: 250 mg every 24 hours. |
| Liver impairment | Child-Pugh Class A: no adjustment; Child-Pugh Class B: reduce dose by 50%; Child-Pugh Class C: avoid use. |
| Pediatric use | 30 mg/kg/day divided every 6 hours orally; maximum 2 g/day. |
| Geriatric use | Initiate at lower end of dosing range; monitor renal function and adjust accordingly. |
| 1st trimester | Contraindicated due to teratogenicity in animal studies. Avoid use in first trimester unless no safer alternative. |
| 2nd trimester | Limited data; may cause fetal harm. Use only if clearly needed and alternatives are not available. |
| 3rd trimester | Potential for neonatal adverse effects (e.g., kernicterus in neonates with G6PD deficiency). Avoid near term. |
Clinical note
Comprehensive clinical and safety monograph for SOXAZOLE (SOXAZOLE).
| Placental transfer | Crosses the placenta in humans; fetal concentrations may reach maternal levels. Animal studies show fetal toxicity. |
| Breastfeeding | Excreted into breast milk in low concentrations. However, potential for kernicterus in infants with G6PD deficiency or hyperbilirubinemia. Avoid breastfeeding during therapy and for 2 weeks after last dose. |
■ FDA Black Box Warning
Sulfonamide antibiotics, including soxazole, have been associated with severe adverse reactions such as Stevens-Johnson syndrome, toxic epidermal necrolysis, and agranulocytosis. Fatalities have occurred.
| Serious Effects |
Hypersensitivity to soxazole or sulfonamidesPorphyriaSevere hepatic or renal impairmentPregnancy (especially 1st and 3rd trimester)BreastfeedingG6PD deficiency
| Precautions | Monitor for hypersensitivity reactions, severe cutaneous adverse reactions (SCARs), hemolytic anemia in G6PD-deficient patients, renal and hepatic impairment, and photosensitivity. |
| Food/Dietary | Avoid acidic foods and beverages (e.g., citrus juices, soda) as they may increase risk of crystalluria. Maintain adequate hydration; alcohol may increase risk of adverse effects. |
Loading safety data…
| Lactation Rating |
| L4 (Hazardous) |
| Teratogenic Risk | First trimester: No evidence of teratogenicity in human studies; animal studies show no fetal harm at therapeutic doses. Second and third trimesters: Risk of decreased amniotic fluid volume due to fetal renal effects; avoid prolonged use near term due to potential premature ductus arteriosus closure. Overall FDA category C. |
| Fetal Monitoring | Monitor maternal renal function, hepatic function, and complete blood count periodically. During pregnancy, monitor amniotic fluid volume via ultrasound if used for extended periods. Assess fetal growth and well-being if used in third trimester. |
| Fertility Effects | No evidence of impaired fertility in animal studies. No human data on fertility effects. Theoretical risk of reversible spermatogenesis suppression with high doses; not clinically significant at recommended doses. |
| Clinical Pearls | Soxazole is a sulfonamide antibiotic; ensure adequate hydration to prevent crystalluria. Monitor for hypersensitivity reactions, especially in patients with G6PD deficiency. Avoid use in infants <2 months due to risk of kernicterus. Consider resistance patterns before empiric use. |
| Patient Advice | Take with a full glass of water and maintain increased fluid intake throughout treatment to prevent kidney problems. · Complete the full course even if you feel better to prevent resistance. · Avoid prolonged sun exposure and use sunscreen; this drug can increase photosensitivity. · Report any rash, fever, sore throat, or unusual bleeding or bruising immediately. · Do not take if you are pregnant, breastfeeding, or have a history of sulfa allergy. |