Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
BACTRIM DS vs GANTANOL
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
BACTRIM DS is a combination of sulfamethoxazole and trimethoprim. Sulfamethoxazole inhibits bacterial synthesis of dihydrofolic acid by competing with para-aminobenzoic acid (PABA), while trimethoprim inhibits dihydrofolate reductase, blocking reduction of dihydrofolate to tetrahydrofolate. This sequential blockade of folic acid synthesis leads to bactericidal action.
Sulfamethoxazole is a sulfonamide that inhibits bacterial dihydropteroate synthase, preventing folate synthesis. Trimethoprim inhibits bacterial dihydrofolate reductase, blocking tetrahydrofolate production. The combination produces sequential blockade of folate metabolism, leading to bactericidal activity.
FDA-approved: Urinary tract infections, acute otitis media, acute exacerbations of chronic bronchitis, traveler's diarrhea, shigellosis, Pneumocystis jirovecii pneumonia (PCP), toxoplasmosis,Off-label: Methicillin-resistant Staphylococcus aureus (MRSA) infections, Stenotrophomonas maltophilia infections, nocardiosis, Wegener's granulomatosis (as second-line therapy), inflammatory bowel disease
Urinary tract infections,Acute otitis media,Acute exacerbations of chronic bronchitis,Traveler's diarrhea,Pneumocystis jirovecii pneumonia (treatment and prophylaxis),Toxoplasmosis (prophylaxis in immunocompromised patients),Shigellosis,Nocardiosis
One double-strength tablet (trimethoprim 160 mg-sulfamethoxazole 800 mg) orally every 12 hours.
800 mg orally every 12 hours for 5-7 days.
Sulfamethoxazole: 8-10 hours; Trimethoprim: 8-12 hours; prolonged in renal impairment (creatinine clearance <30 m L/min: up to 24-48 hours).
Terminal elimination half-life: 8-12 hours in healthy adults; prolonged in renal impairment (up to 24-36 hours in Cr Cl <30 m L/min).
Sulfamethoxazole is metabolized primarily by N-acetylation and glucuronidation; trimethoprim is metabolized by O-demethylation and N-oxidation. Both are eliminated renally via glomerular filtration and tubular secretion.
Sulfamethoxazole is metabolized primarily by N-acetylation and glucuronidation. Trimethoprim undergoes O-demethylation and oxidative metabolism. Both are excreted renally.
Renal: 50-70% as sulfamethoxazole (unchanged and acetylated metabolite), 40-60% as trimethoprim (unchanged); biliary: <10% for both; fecal: <4%.
Renal: 70% as unchanged drug; hepatic metabolism: 20% (glucuronidation); fecal: 10%.
Sulfamethoxazole: 68% bound (albumin); Trimethoprim: 44% bound (albumin, alpha-1-acid glycoprotein).
85-90% primarily to albumin.
Sulfamethoxazole: 0.21 L/kg; Trimethoprim: 1.3-1.8 L/kg (wide distribution, higher in tissues than plasma).
0.15-0.3 L/kg; indicates limited extravascular distribution, primarily confined to plasma and interstitial fluid.
Oral: >90% for both components; IV: 100%.
Oral: 90-95%; Intravenous: 100%.
Cr Cl >30 m L/min: No adjustment; Cr Cl 15-30 m L/min: 50% of usual dose every 12 hours; Cr Cl <15 m L/min: Not recommended.
Cr Cl 30-60 m L/min: 800 mg every 24 hours. Cr Cl 15-29 m L/min: 800 mg every 48 hours. Cr Cl <15 m L/min or hemodialysis: 800 mg every 48-72 hours.
Child-Pugh Class A: No adjustment; Child-Pugh Class B: Use with caution, no specific dose recommendation; Child-Pugh Class C: Contraindicated.
Child-Pugh Class A: no adjustment. Child-Pugh Class B: reduce dose by 50%. Child-Pugh Class C: use contraindicated.
Based on trimethoprim component: 8 mg/kg/day of trimethoprim divided every 12 hours. For severe infections, up to 20 mg/kg/day of trimethoprim divided every 6 hours.
15 mg/kg orally every 6 hours for children 2 months to 12 years; maximum 2 g/day.
Monitor renal function; adjust dose based on Cr Cl. Increased risk of hyperkalemia and folate deficiency; consider folate supplementation.
Use with caution; start at 400 mg every 12 hours due to age-related renal decline. Monitor for toxicity.
BACTRIM DS carries a black box warning for severe hypersensitivity reactions including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and fulminant hepatic necrosis. Also warns about fatal reactions such as agranulocytosis, aplastic anemia, and other blood dyscrasias. Additionally, use in pregnancy at term may cause kernicterus in the newborn.
Fatal hypersensitivity reactions including Stevens-Johnson syndrome, toxic epidermal necrolysis, and hepatic necrosis have occurred. Also associated with fatal hematologic toxicities (e.g., agranulocytosis, aplastic anemia). Coadministration with methotrexate increases risk of megaloblastic anemia.
Hypersensitivity reactions: risk of SJS/TEN, especially in patients with HIV, folate deficiency, or genetic susceptibility (e.g., HLA-B*1502, HLA-A*3101). Discontinue at first sign of rash.,Hematologic toxicity: monitor CBCs; caution in patients with folate deficiency, renal impairment, or prolonged therapy.,Hepatic toxicity: can cause cholestatic jaundice, hepatic necrosis; avoid in hepatic impairment.,Renal toxicity: maintain adequate hydration to prevent crystalluria; adjust dose in renal impairment.,Hyperkalemia: risk with high-dose trimethoprim; monitor potassium, especially in patients with renal dysfunction or on potassium-sparing diuretics.,Hypoglycemia: risk in patients with renal impairment or malnutrition; caution with sulfonylureas.,Photosensitivity: avoid excessive sun exposure.,Pregnancy: avoid at term due to risk of kernicterus; use only if benefit outweighs risk.,Lactation: caution due to potential for kernicterus in infants with G6PD deficiency.
Hypersensitivity and skin reactions (discontinue at first sign of rash). Hemolysis in G6PD-deficient patients. Risk of hepatotoxicity, including cholestatic jaundice and hepatic necrosis. Photosensitivity. Severe renal and hepatic impairment. Use caution in elderly, folate-deficient patients, and those with megaloblastic anemia. Possible hyperkalemia with high-dose treatment in renal impairment.
Hypersensitivity to sulfamethoxazole, trimethoprim, or any component.,History of drug-induced immune thrombocytopenia with sulfonamides or trimethoprim.,Severe hepatic disease (e.g., acute hepatitis, cirrhosis with jaundice).,Severe renal impairment (Cr Cl <15 m L/min) unless dialysis is available.,Megaloblastic anemia due to folate deficiency.,Pregnancy at term and nursing mothers (due to risk of kernicterus).,Concurrent use with dofetilide (increased risk of arrhythmias).,Infants <2 months of age (sulfonamides can cause kernicterus).
Hypersensitivity to sulfonamides, trimethoprim, or any component. History of drug-induced hypersensitivity reactions. Severe hepatic impairment. Severe renal impairment (Cr Cl <15 m L/min) not on dialysis. Megaloblastic anemia due to folate deficiency. Pregnancy (especially first trimester) and lactation (near term). Concurrent use with dofetilide.
Avoid high-potassium foods (e.g., bananas, oranges, potatoes) as trimethoprim can increase serum potassium. Avoid alcohol, which may cause disulfiram-like reaction (flushing, nausea, tachycardia). No significant food-drug interactions beyond potassium and alcohol.
Avoid alcohol during and for 3 days after therapy. Limit high-potassium foods if using high doses. Take with food to reduce GI upset.
First trimester: Folate antagonist; associated with neural tube defects, cardiovascular malformations, and cleft palate. Second trimester: Growth restriction, preterm birth. Third trimester: Kernicterus risk due to bilirubin displacement from albumin. Avoid during entire pregnancy.
First trimester: Sulfonamides cross the placenta; risk of kernicterus in neonates if used near term. Animal studies show cleft palate and other anomalies at high doses. Human data insufficient; avoid use in first trimester unless benefit outweighs risk. Second/third trimester: Risk of neonatal jaundice and hemolytic anemia in G6PD deficiency; contraindicated after 38 weeks or near delivery due to kernicterus risk.
Breastfeeding safety: Both trimethoprim and sulfamethoxazole are excreted into breast milk; M/P ratio for trimethoprim ~1.25, sulfamethoxazole ~0.15. Caution in infants under 2 months or with G6PD deficiency; theoretical risk of kernicterus.
Sulfamethoxazole is excreted into breast milk with a milk-to-plasma ratio of approximately 0.1. Based on limited data, not recommended in nursing mothers at term due to potential for neonatal kernicterus and hemolysis in G6PD-deficient infants; caution if used in preterm or jaundiced infants.
No standard dose adjustment recommended; avoid use if possible. If necessary, ensure adequate folic acid intake; may need to increase dose due to increased clearance in pregnancy, but specific data lacking.
No specific dose adjustments required for pregnancy alone. Consider increased clearance in pregnancy; monitor for therapeutic efficacy. Use lowest effective dose for shortest duration.
Bactrim DS (sulfamethoxazole/trimethoprim) is contraindicated in G6PD deficiency due to risk of hemolytic anemia. Monitor for hyperkalemia, especially in elderly or those with renal impairment. Caution with warfarin (potentiates anticoagulation). Avoid in pregnancy (teratogenic) and lactation. Use with caution in folate deficiency; supplement folate if needed.
Gantanol (sulfamethoxazole) is a sulfonamide antibiotic often used in combination with trimethoprim (co-trimoxazole). Monitor for hypersensitivity reactions, especially in HIV patients. Adjust dose in renal impairment (Cr Cl <30 m L/min avoid). Hydrate to prevent crystalluria.
Take with a full glass of water and stay well-hydrated to prevent crystalluria.,Avoid prolonged sun exposure; use sunscreen as this drug may cause photosensitivity.,Complete the full course even if you feel better to prevent antibiotic resistance.,Report any skin rash, sore throat, fever, or unusual bleeding immediately.,Do not take if you are pregnant, planning to become pregnant, or breastfeeding.,Inform your doctor if you have kidney disease, G6PD deficiency, or are on blood thinners.
Take with a full glass of water to prevent kidney stones.,Complete full course even if feeling better.,Avoid prolonged sun exposure; use sunscreen.,Report rash, fever, or sore throat immediately.,Do not use if allergic to sulfa drugs.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about BACTRIM DS vs GANTANOL, answered by our medical review team.
BACTRIM DS is a Sulfonamide Antibiotic Combination that works by BACTRIM DS is a combination of sulfamethoxazole and trimethoprim. Sulfamethoxazole inhibits bacterial synthesis of dihydrofolic acid by competing with para-aminobenzoic acid (PABA), while trimethoprim inhibits dihydrofolate reductase, blocking reduction of dihydrofolate to tetrahydrofolate. This sequential blockade of folic acid synthesis leads to bactericidal action.. GANTANOL is a Sulfonamide Antibiotic that works by Sulfamethoxazole is a sulfonamide that inhibits bacterial dihydropteroate synthase, preventing folate synthesis. Trimethoprim inhibits bacterial dihydrofolate reductase, blocking tetrahydrofolate production. The combination produces sequential blockade of folate metabolism, leading to bactericidal activity.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between BACTRIM DS and GANTANOL depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of BACTRIM DS is: One double-strength tablet (trimethoprim 160 mg-sulfamethoxazole 800 mg) orally every 12 hours.. The standard adult dose of GANTANOL is: 800 mg orally every 12 hours for 5-7 days.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between BACTRIM DS and GANTANOL in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. BACTRIM DS is classified as Category C. First trimester: Folate antagonist; associated with neural tube defects, cardiovascular malformations, and cleft palate. Second trimester: Growth restriction, preterm birth. Third . GANTANOL is classified as Category C. First trimester: Sulfonamides cross the placenta; risk of kernicterus in neonates if used near term. Animal studies show cleft palate and other anomalies at high doses. Human data . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.