Comparative Pharmacology
Head-to-head clinical analysis: SEPTRA versus SULFAMETHOXAZOLE AND TRIMETHOPRIM DOUBLE STRENGTH.
Peer-Reviewed Evidence
Head-to-head clinical analysis: SEPTRA versus SULFAMETHOXAZOLE AND TRIMETHOPRIM DOUBLE STRENGTH.
SEPTRA vs SULFAMETHOXAZOLE AND TRIMETHOPRIM DOUBLE STRENGTH
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
SEPTRA (trimethoprim/sulfamethoxazole) is a combination of two antifolate agents: sulfamethoxazole inhibits dihydropteroate synthase, blocking the conversion of PABA to dihydrofolic acid; trimethoprim inhibits dihydrofolate reductase, preventing the reduction of dihydrofolic acid to tetrahydrofolic acid. This sequential blockade disrupts bacterial folate synthesis and nucleic acid production.
Sulfamethoxazole inhibits bacterial dihydropteroate synthase, blocking folic acid synthesis. Trimethoprim inhibits bacterial dihydrofolate reductase, blocking reduction of dihydrofolate to tetrahydrofolate. Sequential blockade produces bactericidal effect.
Trimethoprim-sulfamethoxazole (TMP-SMX) 160 mg/800 mg (double strength) orally every 12 hours; for severe infections, intravenous dosing: 8-10 mg/kg/day (TMP component) divided every 6, 8, or 12 hours.
One double-strength tablet (160 mg trimethoprim/800 mg sulfamethoxazole) orally every 12 hours.
None Documented
None Documented
Sulfamethoxazole: 9-12 hours (normal renal function); Trimethoprim: 8-11 hours (normal renal function). In severe renal impairment (CrCl <15 mL/min), half-life prolongs significantly (up to 24-30 hours for sulfamethoxazole, 20-30 hours for trimethoprim).
Sulfamethoxazole: 9-11 hours; trimethoprim: 8-11 hours. In severe renal impairment (CrCl <15 mL/min), half-life prolongs significantly (up to 30 hours for trimethoprim).
Renal excretion of unchanged sulfamethoxazole (~20%) and trimethoprim (~50-60%) with additional hepatic metabolism (acetylation, glucuronidation) of sulfamethoxazole; total renal elimination accounts for ~80-90% of the dose (sulfamethoxazole 30% parent, 40% metabolites; trimethoprim 60-80% parent, remainder as metabolites). Biliary/fecal <5%.
Both sulfamethoxazole and trimethoprim are primarily excreted via the kidneys. Sulfamethoxazole: ~30% as unchanged drug, ~50% as N4-acetyl metabolite; trimethoprim: ~80% as unchanged drug. Fecal elimination is minimal (<5%).
Category C
Category D/X
Antibiotic
Antibiotic