TRYSUL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TRYSUL (TRYSUL).
Trypanocidal agent; forms a complex with DNA and inhibits nucleic acid synthesis.
| Metabolism | Hepatic; undergoes N-demethylation and hydroxylation via cytochrome P450 enzymes (CYP3A4). |
| Excretion | Renal: approximately 70-80% as unchanged drug via glomerular filtration and tubular secretion; biliary/fecal: 15-20% as metabolites; small amount in feces. |
| Half-life | Terminal elimination half-life: 8-10 hours in adults with normal renal function; prolonged to 20-30 hours in severe renal impairment (CrCl <30 mL/min). |
| Protein binding | 95-98% bound primarily to albumin; minor binding to alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.15-0.3 L/kg, indicating distribution primarily in extracellular fluid and plasma. |
| Bioavailability | Oral: 80-95% (first-pass metabolism negligible). |
| Onset of Action | Oral: 30-60 minutes; intravenous: immediate (within minutes). |
| Duration of Action | 6-12 hours for oral, 4-8 hours for intravenous; dosing interval adjusted based on renal function. |
| Molecular Weight | Trimethoprim: 290.32 Da; Sulfamethoxazole: 253.28 Da |
2 tablets (each containing sulfamethoxazole 400 mg and trimethoprim 80 mg) orally every 12 hours for 10-14 days.
| Dosage form | CREAM |
| Renal impairment | CrCl >30 mL/min: no adjustment; CrCl 15-30 mL/min: 50% of usual dose every 12 hours; CrCl <15 mL/min: not recommended. |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C); use with caution in moderate impairment (Child-Pugh class B) with monitoring; no dosage adjustment in mild impairment (Child-Pugh class A). |
| Pediatric use | 8-12 mg/kg/day of trimethoprim component divided every 12 hours; for severe infections, up to 20 mg/kg/day of trimethoprim component divided every 6-8 hours. Maximum: 320 mg/day of trimethoprim component. |
| Geriatric use | Initiate at lower end of dosing range due to age-related renal function decline; monitor renal function and adjust dose accordingly; consider folate supplementation. |
| 1st trimester | Avoid; sulfonamides and trimethoprim may cause neural tube defects and other congenital anomalies due to folate antagonism. |
| 2nd trimester | Use only if clearly needed; potential risk of kernicterus in neonate due to bilirubin displacement. |
| 3rd trimester | Contraindicated; risk of hemolytic anemia, kernicterus, and neonatal hyperbilirubinemia. |
Clinical note
Comprehensive clinical and safety monograph for TRYSUL (TRYSUL).
| Placental transfer | Both components cross the placenta; sulfamethoxazole reaches fetal serum concentrations 50-90% of maternal levels; trimethoprim crosses readily. |
| Breastfeeding | Both sulfamethoxazole and trimethoprim are excreted into breast milk. Use with caution in nursing mothers, especially if infant is jaundiced, ill, or premature; risk of kernicterus and sulfonamide-induced hemolysis in G6PD-deficient infants. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to sulfonamides, trimethoprim, or any componentMegaloblastic anemia due to folate deficiencySevere hepatic impairmentSevere renal impairment (CrCl <15 mL/min)Pregnancy (especially third trimester) and lactation (in certain situations)Concomitant use with dofetilide
| Precautions | Cardiotoxicity (QT prolongation, arrhythmias); encephalopathy; hypersensitivity reactions; monitor ECG, hepatic function, and electrolytes. |
| Food/Dietary | Avoid potassium-rich foods (e.g., bananas, oranges, potatoes) and potassium supplements due to increased hyperkalemia risk. Limit alcohol consumption as may cause disulfiram-like reaction. Ensure adequate fluid intake (2-3 L/day) to prevent crystalluria. |
Loading safety data…
| Lactation Rating | L3 (Limited data; potential adverse effects) |
| Teratogenic Risk | TRYSUL (trimethoprim/sulfamethoxazole) is contraindicated in pregnancy due to teratogenic risks. First trimester: Sulfonamides are associated with neural tube defects, cardiovascular anomalies, and oral clefts (folate antagonist). Second and third trimesters: Risk of kernicterus in neonates; trimethoprim may cause folic acid deficiency and neural tube defects. Category D. |
| Fetal Monitoring | Monitor CBC, renal function, and folate levels during pregnancy. Assess fetal neural tube development via ultrasound in first trimester. In third trimester, monitor for neonatal jaundice, kernicterus. Advise folate supplementation. |
| Fertility Effects | TRMS may impair folate metabolism, potentially affecting ovulation and spermatogenesis. Folate supplementation recommended for both sexes attempting conception. No conclusive evidence of permanent fertility impairment. |
| Clinical Pearls | TRYSul (trimethoprim/sulfamethoxazole) is a fixed-dose combination antibiotic. Monitor renal function and potassium levels due to risk of hyperkalemia, especially in elderly or those with renal impairment. Avoid in patients with sulfonamide allergy. Use with caution in G6PD deficiency due to hemolytic anemia risk. Prolonged use may lead to bone marrow suppression; obtain CBC at baseline and periodically. |
| Patient Advice | Take with a full glass of water to prevent crystalluria. · Complete the full course even if you feel better. · Avoid prolonged sun exposure; use sunscreen as photosensitivity may occur. · Report any rash, sore throat, fever, or unusual bleeding to your doctor. · Do not use if you are allergic to sulfa drugs or trimethoprim. |