SULFAIR-15
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SULFAIR-15 (SULFAIR-15).
Sulfadoxine is a long-acting sulfonamide that inhibits dihydropteroate synthase, blocking folate synthesis. Pyrimethamine inhibits dihydrofolate reductase, synergistically inhibiting nucleic acid synthesis in Plasmodium species.
| Metabolism | Sulfadoxine is metabolized via acetylation and glucuronidation in the liver. Pyrimethamine is metabolized in the liver by CYP2C9 and other pathways. |
| Excretion | Renal excretion unchanged: 70%; hepatic metabolism to inactive metabolites: 20%; fecal excretion: 10%. |
| Half-life | 12–15 hours in healthy adults; prolonged to 20–30 hours in moderate hepatic impairment. |
| Protein binding | 98% bound to albumin. |
| Volume of Distribution | 0.15 L/kg, indicating limited extravascular distribution. |
| Bioavailability | Oral: 85%; intramuscular: 100%. |
| Onset of Action | Oral: 30–60 minutes; IV: 5–10 minutes. |
| Duration of Action | 8–12 hours following single oral dose; 12–18 hours after multiple doses due to accumulation. |
15 mg orally every 6 hours, not to exceed 60 mg/day.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | GFR ≥ 60 mL/min: no adjustment; GFR 30-59: 15 mg every 8 hours; GFR 15-29: 15 mg every 12 hours; GFR <15: avoid use. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: contraindicated. |
| Pediatric use | 0.5 mg/kg orally every 6 hours, maximum 60 mg/day; not recommended under 1 year. |
| Geriatric use | Initial dose 7.5 mg every 6 hours; titrate to response; monitor renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for SULFAIR-15 (SULFAIR-15).
| Breastfeeding | SMX/TMP is excreted into breast milk. M/P ratio for sulfamethoxazole is approximately 0.5-0.7; for trimethoprim, 0.7-1.5. Monitor infant for jaundice, rash, and diarrhea. Avoid in breastfeeding infants with G6PD deficiency or hyperbilirubinemia. |
| Teratogenic Risk | First trimester: Sulfamethoxazole/trimethoprim (SMX/TMP) is associated with increased risk of neural tube defects, cardiovascular malformations, and oral clefts. Second/third trimester: Risk of kernicterus due to bilirubin displacement; avoid near term. |
■ FDA Black Box Warning
Fatal hypersensitivity reactions, including Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), have been reported. Contraindicated in patients with a history of sulfonamide hypersensitivity.
| Serious Effects |
Hypersensitivity to sulfonamides or pyrimethamine; severe hepatic or renal impairment; megaloblastic anemia due to folate deficiency; pregnancy (first trimester) and lactation (potential harm to infant).
| Precautions | Risk of severe cutaneous adverse reactions (SJS/TEN); bone marrow suppression (especially with prolonged use); folate deficiency; hypersensitivity reactions; hematologic monitoring recommended. |
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| Fetal Monitoring |
| Monitor maternal CBC (especially platelets and WBC), renal function, and liver enzymes. Fetal ultrasound for anomalies if exposed in first trimester. Monitor for neonatal hyperbilirubinemia and kernicterus if administered near delivery. |
| Fertility Effects | SMX/TMP may impair folate metabolism, potentially reducing fertility due to antifolate effects. In males, may cause reversible oligospermia. Discontinuation typically restores normal fertility. |