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. |
| Molecular Weight | 300 |
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 | Contraindicated due to risk of fetal harm (known teratogen). Avoid use during first trimester unless no safer alternative exists. |
| 2nd trimester | Limited data; potential fetal CNS and cardiovascular effects. Use only if benefit outweighs risk. |
| 3rd trimester | Avoid near term due to neonatal withdrawal syndrome. Use only if clearly needed. |
Clinical note
Comprehensive clinical and safety monograph for SULFAIR FORTE (SULFAIR FORTE).
| Placental transfer | Crosses placenta (animal data). Human data limited; expect significant transfer due to molecular weight. |
| Breastfeeding | Excreted in breast milk in low amounts. Theoretical risk of kernicterus in neonates, especially those with G6PD deficiency. Use caution and monitor infant for jaundice. |
■ 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 sulfonamidesSevere hepatic impairmentPorphyriaG6PD deficiency
| Precautions | Folate deficiency; hemolytic anemia in G6PD deficiency; hypersensitivity reactions; photosensitivity; renal impairment. |
| Food/Dietary | Avoid alcohol during treatment and for 3 days after. Limit high-potassium foods (bananas, oranges, spinach, salt substitutes) if on ACE inhibitors or potassium-sparing diuretics. Avoid folic acid supplements unless prescribed. Increase fluid intake to prevent kidney stones. |
Loading safety data…
| Lactation Rating |
| L3 (Moderately Safe) |
| 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 | 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. |
| Clinical Pearls |
| Sulfair Forte is a combination of sulfamethoxazole and trimethoprim. Monitor for hypersensitivity reactions, especially in HIV patients. Adjust dose in renal impairment (CrCl <30 mL/min contraindicated). Avoid in G6PD deficiency due to hemolysis risk. Use with caution in elderly and those with folic acid deficiency. Drug interactions: warfarin (increased INR), methotrexate (toxicity), sulfonylureas (hypoglycemia). |
| Patient Advice | Complete full course even if you feel better. · Take with a full glass of water to prevent crystalluria. · Avoid sunlight/UV exposure; use sunscreen. · Report rash, fever, sore throat, or unusual bleeding. · Not for use in pregnancy (especially 3rd trimester) or breastfeeding. · Avoid alcohol (may cause disulfiram-like reaction). · Do not take if allergic to sulfa drugs or have severe kidney disease. |