TRIPLE SULFAS

Clinical safety rating: caution

Comprehensive clinical and safety monograph for TRIPLE SULFAS (TRIPLE SULFAS).

How it works

Competitive inhibition of dihydropteroate synthase, thereby blocking folate synthesis and bacterial DNA replication. Triple sulfas (sulfadiazine, sulfamerazine, sulfamethazine) act synergistically to inhibit folic acid synthesis.

What the body does with it

Metabolism	Primarily hepatic acetylation to inactive metabolites; also conjugation with glucuronic acid. Metabolites are renally excreted. Sulfamethazine is acetylated at a slower rate.
Excretion	Primarily renal; approximately 70-100% excreted unchanged in urine via glomerular filtration and tubular secretion. Minor biliary/fecal elimination (<5%) with enterohepatic circulation possible.
Half-life	Terminal elimination half-life ranges from 10-12 hours in adults with normal renal function. Prolonged in renal impairment (up to 24-48 hours) and neonates (40-120 hours).
Protein binding	Sulfamethazine: 60-80%; sulfamerazine: 70-80%; sulfadiazine: 20-50%. Primary binding proteins: albumin (weakly, with displacement interactions).
Volume of Distribution	0.3-0.6 L/kg for individual sulfonamides; combined Vd approximately 0.4 L/kg, indicating distribution into total body water with some tissue binding.
Bioavailability	Oral: approximately 85-95% for the combination; well absorbed from GI tract. Intravenous: 100%.
Onset of Action	Oral: 1-2 hours for bacteriostatic effect; peak serum concentrations at 2-4 hours. Intravenous: immediate onset; peak at end of infusion.
Duration of Action	6-12 hours; clinical effect lasts approximately 12 hours after oral dose. Use every 6 hours for continuous coverage. Longer duration in renal impairment.

Classification & Brands

Dosing & administration

1 to 2 tablets (each containing sulfadiazine 167 mg, sulfamerazine 167 mg, sulfamethazine 167 mg) orally every 4 hours initially, then 2 tablets every 6 hours. Maximum daily dose: 6 grams of total sulfonamide.

Dosage form	SUSPENSION
Renal impairment	GFR 30-50 mL/min: administer 75% of normal dose every 12 hours. GFR 10-29 mL/min: administer 50% of normal dose every 12-18 hours. GFR <10 mL/min: contraindicated.
Liver impairment	Child-Pugh Class A: no adjustment. Child-Pugh Class B: reduce dose by 25-50% and monitor for toxicity. Child-Pugh Class C: contraindicated.
Pediatric use	Children >2 months: initial loading dose of 75 mg/kg (based on total sulfonamide) orally, then 150 mg/kg/day divided every 6 hours. Maximum daily dose: 6 grams.
Geriatric use	Initiate at lower end of dosing range (e.g., 1 tablet every 6 hours) due to age-related renal impairment. Monitor renal function and adjust dose based on GFR.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for TRIPLE SULFAS (TRIPLE SULFAS).

Breastfeeding	Sulfonamides are excreted into breast milk in low concentrations (M/P ratio ~0.2-0.4). Risk of kernicterus in jaundiced or G6PD-deficient infants; avoid in nursing mothers of ill or premature infants.
Teratogenic Risk	Sulfonamides cross the placenta. First trimester: association with neural tube defects, cardiovascular anomalies. Third trimester: risk of kernicterus in neonate due to bilirubin displacement from albumin; avoid near term.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

Fatalities have occurred due to severe reactions including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias. Do not use in patients with hypersensitivity to sulfonamides.

Side Effect Profile

Serious Effects

Absolute Contraindications

Hypersensitivity to sulfonamides, sulfonylureas, thiazide diuretics, or carbonic anhydrase inhibitors. Infants <2 months of age (except for congenital toxoplasmosis). Pregnancy (risk of kernicterus in newborns). Lactation (risk in nursing infants). Porphyria. Severe renal or hepatic impairment.

Clinical Precautions

Precautions

Serious hypersensitivity reactions (e.g., Stevens-Johnson syndrome) may occur; discontinue at first sign of rash. Potential for blood dyscrasias, crystalluria with renal damage (ensure adequate hydration). Use caution in patients with renal or hepatic impairment, G6PD deficiency (risk of hemolytic anemia), and porphyria. May cause photosensitivity.

Clinical Tips & Counseling

Drug interactions

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TRIPLE SULFAS

Clinical safety rating: caution

Comprehensive clinical and safety monograph for TRIPLE SULFAS (TRIPLE SULFAS).

How it works

What the body does with it

Metabolism	Primarily hepatic acetylation to inactive metabolites; also conjugation with glucuronic acid. Metabolites are renally excreted. Sulfamethazine is acetylated at a slower rate.
Excretion	Primarily renal; approximately 70-100% excreted unchanged in urine via glomerular filtration and tubular secretion. Minor biliary/fecal elimination (<5%) with enterohepatic circulation possible.
Half-life	Terminal elimination half-life ranges from 10-12 hours in adults with normal renal function. Prolonged in renal impairment (up to 24-48 hours) and neonates (40-120 hours).
Protein binding	Sulfamethazine: 60-80%; sulfamerazine: 70-80%; sulfadiazine: 20-50%. Primary binding proteins: albumin (weakly, with displacement interactions).
Volume of Distribution	0.3-0.6 L/kg for individual sulfonamides; combined Vd approximately 0.4 L/kg, indicating distribution into total body water with some tissue binding.
Bioavailability	Oral: approximately 85-95% for the combination; well absorbed from GI tract. Intravenous: 100%.
Onset of Action	Oral: 1-2 hours for bacteriostatic effect; peak serum concentrations at 2-4 hours. Intravenous: immediate onset; peak at end of infusion.
Duration of Action	6-12 hours; clinical effect lasts approximately 12 hours after oral dose. Use every 6 hours for continuous coverage. Longer duration in renal impairment.

Classification & Brands

Dosing & administration

Dosage form	SUSPENSION
Renal impairment	GFR 30-50 mL/min: administer 75% of normal dose every 12 hours. GFR 10-29 mL/min: administer 50% of normal dose every 12-18 hours. GFR <10 mL/min: contraindicated.
Liver impairment	Child-Pugh Class A: no adjustment. Child-Pugh Class B: reduce dose by 25-50% and monitor for toxicity. Child-Pugh Class C: contraindicated.
Pediatric use	Children >2 months: initial loading dose of 75 mg/kg (based on total sulfonamide) orally, then 150 mg/kg/day divided every 6 hours. Maximum daily dose: 6 grams.
Geriatric use	Initiate at lower end of dosing range (e.g., 1 tablet every 6 hours) due to age-related renal impairment. Monitor renal function and adjust dose based on GFR.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for TRIPLE SULFAS (TRIPLE SULFAS).

Breastfeeding	Sulfonamides are excreted into breast milk in low concentrations (M/P ratio ~0.2-0.4). Risk of kernicterus in jaundiced or G6PD-deficient infants; avoid in nursing mothers of ill or premature infants.
Teratogenic Risk	Sulfonamides cross the placenta. First trimester: association with neural tube defects, cardiovascular anomalies. Third trimester: risk of kernicterus in neonate due to bilirubin displacement from albumin; avoid near term.
Fetal Monitoring