SULFAIR FORTE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SULFAIR FORTE (SULFAIR FORTE).
Folate antagonist; inhibits dihydropteroate synthetase in bacterial folate synthesis pathway.
| Metabolism | Hepatic metabolism via N-acetylation and glucuronidation. |
| Excretion | Primarily renal excretion of unchanged drug (approx. 70-80%) and glucuronide conjugates; biliary excretion accounts for less than 20%; fecal elimination minimal. |
| Half-life | Approximately 10-12 hours in patients with normal renal function; prolonged in renal impairment (up to 20-30 hours), necessitating dose adjustment. |
| Protein binding | Approximately 90-95% bound to serum albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.15-0.2 L/kg, indicating limited extravascular distribution; primarily confined to extracellular fluid. |
| Bioavailability | Oral: 85-90%; topical: negligible systemic absorption (<5%). |
| Onset of Action | Oral: 1-2 hours; Intravenous: within 15-30 minutes. |
| Duration of Action | Oral: 6-8 hours; Intravenous: 4-6 hours; clinical effect correlates with serum concentration above minimum inhibitory concentration. |
1-2 tablets (sulfamethoxazole 400 mg/trimethoprim 80 mg per tablet) orally every 12 hours.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | GFR >30 mL/min: no adjustment; GFR 15-30 mL/min: 50% of standard dose every 12 hours; GFR <15 mL/min: contraindicated. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: use with caution, monitor hepatic function; Child-Pugh C: contraindicated. |
| Pediatric use | 6-12 years: 1 tablet (400/80 mg) every 12 hours; >12 years: adult dose; <6 years: not recommended (suspension available for younger children: 8 mg/kg/day trimethoprim divided every 12 hours). |
| Geriatric use | Monitor renal function; adjust dose based on GFR; avoid in patients with GFR <15 mL/min; increased risk of hyperkalemia with ACE inhibitors or potassium-sparing diuretics. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for SULFAIR FORTE (SULFAIR FORTE).
| Breastfeeding | Sulfadiazine excreted in breast milk; M/P ratio ~0.5-1.0. Avoid in infants with G6PD deficiency or hyperbilirubinemia. Use with caution. |
| Teratogenic Risk | First trimester: Sulfadiazine crosses placenta; theoretical risk of folate antagonism with neural tube defects. Second/third trimesters: Risk of kernicterus in neonate due to bilirubin displacement; avoid near term. |
| Fetal Monitoring |
■ FDA Black Box Warning
Do not use in pregnant women at term or in nursing mothers because sulfonamides cross the placenta and are excreted in breast milk and may cause kernicterus.
| Serious Effects |
Hypersensitivity to sulfonamides or sulfonylureas; severe hepatic or renal impairment; porphyria; pregnancy at term and lactation.
| Precautions | Folate deficiency; hemolytic anemia in G6PD deficiency; hypersensitivity reactions; photosensitivity; renal impairment. |
Loading safety data…
| Monitor maternal CBC, LFTs, renal function. Fetal ultrasound anomaly scan in first trimester. Assess neonatal bilirubin and G6PD status after delivery. |
| Fertility Effects | No specific human data; animal studies show no significant impact on fertility. Potential reversible inhibition of spermatogenesis in males. |