SULFAIR 10
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SULFAIR 10 (SULFAIR 10).
Bacteriostatic inhibitor of dihydropteroate synthase, blocking folic acid synthesis in susceptible bacteria.
| Metabolism | Primarily hepatic via acetylation and glucuronidation; metabolites are inactive. |
| Excretion | Renal excretion of unchanged drug (approximately 70-80%) and hepatic metabolism (20-30% as metabolites). Fecal elimination is minimal (<5%). |
| Half-life | Terminal elimination half-life of 8-12 hours in adults with normal renal function (CrCl >60 mL/min); extends to 20-30 hours in severe renal impairment (CrCl <30 mL/min), requiring dose adjustment. |
| Protein binding | Approximately 85-90% bound to albumin. |
| Volume of Distribution | 0.35-0.45 L/kg (moderate tissue distribution; primarily extracellular fluid). |
| Bioavailability | Oral: 70-80% (fasting); reduced by 20% with food. Intravenous: 100%. |
| Onset of Action | Oral: 1-2 hours; Intravenous: 15-30 minutes (time to therapeutic plasma concentration). |
| Duration of Action | 12-24 hours (dosing interval q12-24h depending on infection severity and renal function). Prolonged in hepatic impairment. |
| Molecular Weight | 310.33 |
5 mg orally once daily, taken at bedtime.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | GFR ≥60 mL/min: no adjustment. GFR 30-59 mL/min: 2.5 mg once daily. GFR 15-29 mL/min: use alternative therapy. GFR <15 mL/min: contraindicated. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50%. Child-Pugh C: contraindicated. |
| Pediatric use | Not recommended for use in pediatric patients. |
| Geriatric use | Initiate at 2.5 mg once daily; titrate cautiously due to increased sensitivity. |
| 1st trimester | Contraindicated due to theoretical risk of interference with folate metabolism and neural tube defects; animal studies show teratogenicity. |
| 2nd trimester | Contraindicated unless essential; may cause kernicterus in neonate and maternal hemolytic anemia in G6PD deficiency. |
| 3rd trimester | Contraindicated in third trimester; risk of kernicterus and bilirubin displacement in neonate. |
Clinical note
Comprehensive clinical and safety monograph for SULFAIR 10 (SULFAIR 10).
| Placental transfer | Sulfadoxine crosses the placenta readily, achieving fetal concentrations approximately 50-80% of maternal levels; competes with bilirubin for albumin binding. |
| Breastfeeding | Sulfadoxine is excreted in breast milk in low amounts, but risk of kernicterus in neonates, especially those with G6PD deficiency or jaundice; avoid breastfeeding if mother or infant has G6PD deficiency. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to sulfonamides or any componentSevere hepatic parenchymal damageSevere renal insufficiency (CrCl <15 mL/min)PorphyriaG6PD deficiencyInfants <2 months of ageThird trimester of pregnancyLactation in infants with G6PD deficiency or hyperbilirubinemia
| Precautions | May cause hypersensitivity reactions including Stevens-Johnson syndrome; caution in renal impairment, hepatic impairment, glucose-6-phosphate dehydrogenase deficiency; monitor for crystalluria. |
| Food/Dietary | Avoid alcohol during treatment and for 3 days after completion to prevent disulfiram-like reaction. High potassium foods (e.g., bananas, oranges, potatoes) can be consumed with caution as TMP-SMX may increase serum potassium; monitor in patients with renal impairment or on ACE inhibitors. |
Loading safety data…
| Lactation Rating | L4 - Possibly Hazardous |
| Teratogenic Risk | Sulfair 10 contains sulfadoxine and pyrimethamine. In first trimester: crosses placenta; associated with congenital malformations (neural tube defects, cardiovascular anomalies) due to antimalarial effects; advised only if benefit outweighs risk. In second/third trimester: risk of hemolytic anemia in G6PD-deficient fetuses; kernicterus theoretically possible in third trimester due to bilirubin displacement; avoid near term. |
| Fetal Monitoring | Maternal: CBC with platelets, liver function tests weekly during treatment. Fetal: ultrasound for neural tube defects if exposure in first trimester; monitor for jaundice, hemolysis in neonate. |
| Fertility Effects | No known direct effects on fertility; untreated malaria may impair fertility and increase pregnancy complications; treatment of malaria may preserve fertility. |
| Clinical Pearls | SULFAIR 10 (sulfamethoxazole 200 mg/trimethoprim 40 mg) is a fixed-dose combination antibiotic used primarily for urinary tract infections. Due to the low dose, it is not suitable for Pneumocystis jirovecii pneumonia treatment; use high-dose TMP-SMX instead. Monitor for hypersensitivity reactions, especially in HIV patients. Adjust dose in renal impairment (CrCl <30 mL/min: avoid). Avoid in infants <2 months due to kernicterus risk. Note that sulfonamides can cause photosensitivity. |
| Patient Advice | Take with a full glass of water to prevent crystalluria. · Complete the entire course even if you feel better. · Avoid prolonged sun exposure; use sunscreen and wear protective clothing. · Report any rash, fever, or sore throat immediately as these may indicate serious side effects. · If you have G6PD deficiency, inform your doctor before taking this medication. |