Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
CETAMIDE vs BACTRIM PEDIATRIC
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
CETAMIDE is an antimicrobial combination of sulfadiazine (a sulfonamide) and trimethoprim. Sulfonamides inhibit dihydropteroate synthase, blocking folate synthesis; trimethoprim inhibits dihydrofolate reductase, producing sequential blockade of folic acid metabolism.
Bactrim (sulfamethoxazole/trimethoprim) 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. Sequential blockade of folate synthesis leads to bacteriostasis.
Urinary tract infections,Acute otitis media,Shigellosis,Pneumocystis jirovecii pneumonia,Traveler's diarrhea (off-label)
Urinary tract infections due to susceptible strains of E. coli, Klebsiella, Enterobacter, Morganella, Proteus, and Providencia,Acute otitis media in children,Acute exacerbations of chronic bronchitis in adults,Shigellosis,Pneumocystis jirovecii pneumonia (PCP) prophylaxis and treatment,Traveler's diarrhea (FDA-approved),Toxoplasmosis (off-label),Nocardiosis (off-label),Chancroid (off-label),Brucellosis (off-label)
500 mg orally every 6 hours; maximum 4 g per day.
Oral: 160 mg trimethoprim / 800 mg sulfamethoxazole (one DS tablet) every 12 hours for 14 days. For Pneumocystis jirovecii pneumonia: 15-20 mg/kg/day of trimethoprim component divided every 6-8 hours.
6-8 hours; prolonged (up to 30 hours) in severe renal impairment (Cr Cl <30 m L/min).
Sulfamethoxazole: 9-12 hours (prolonged in renal impairment; up to 30 hours with Cr Cl <30 m L/min). Trimethoprim: 8-10 hours (prolonged to 20-30 hours in severe renal impairment).
Sulfadiazine is metabolized via acetylation (N-acetyltransferase) and glucuronidation; trimethoprim is metabolized by oxidative pathways (N-oxidation, N-demethylation) and conjugated with glucuronic acid.
Sulfamethoxazole is metabolized via acetylation and glucuronidation; trimethoprim is metabolized via oxidation (demethylation) and conjugation. CYP450 enzymes have minor involvement.
Primarily renal (85-90%) as unchanged drug; biliary/fecal (5-10%).
Renal: sulfamethoxazole 85% (30% unchanged, rest as acetylated and glucuronide conjugates), trimethoprim 60-80% (10-30% unchanged). Fecal/biliary: <4%.
20-25% bound to albumin.
Sulfamethoxazole: 70% bound to albumin. Trimethoprim: 42-46% bound to albumin and alpha-1-acid glycoprotein.
0.5-0.8 L/kg; indicates distribution into total body water.
Sulfamethoxazole: 0.15-0.3 L/kg. Trimethoprim: 1.3-2.0 L/kg indicating extensive tissue distribution.
Oral: 90-100% (well absorbed).
Oral: sulfamethoxazole 100%; trimethoprim 100% (both well absorbed).
Cr Cl 10-50 m L/min: 250 mg every 6 hours. Cr Cl <10 m L/min: 250 mg every 12 hours.
Cr Cl >30 m L/min: No adjustment. Cr Cl 15-30 m L/min: Reduce dose by 50% (e.g., one DS tablet every 24 hours). Cr Cl <15 m L/min: Contraindicated (unless with hemodialysis). For PJP: Cr Cl 15-29 m L/min: 15-20 mg/kg/day (trimethoprim) divided every 8 hours; Cr Cl <15 m L/min: Not recommended.
Child-Pugh Class C: avoid use; Class A or B: no adjustment needed.
Child-Pugh Class A: No adjustment. Child-Pugh Class B: Caution; consider reducing dose or monitoring liver function. Child-Pugh Class C: Avoid use due to potential hepatotoxicity and altered metabolism.
10-15 mg/kg orally every 6 hours; maximum 100 mg/kg/day.
Trimethoprim component dosing: 8 mg/kg/day divided every 12 hours for urinary tract infection or otitis media. For Pneumocystis jirovecii pneumonia (PJP) prophylaxis: 150 mg/m2/day of trimethoprim divided every 12 hours, given 3 times per week. For PJP treatment: 15-20 mg/kg/day of trimethoprim divided every 6-8 hours. Maximum daily dose: 960 mg trimethoprim.
Consider dose reduction based on renal function; initial dose not to exceed 2 g per day.
Monitor renal function and adjust dose based on Cr Cl. Increased risk of hyperkalemia, hematologic toxicity, and adverse reactions. Consider starting at lower end of dosing range. Avoid in patients with Cr Cl <15 m L/min.
Sulfonamides have been associated with fatal reactions such as Stevens-Johnson syndrome, toxic epidermal necrolysis, agranulocytosis, aplastic anemia, and other blood dyscrasias.
Fatalities associated with sulfonamide hypersensitivity reactions including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias have been reported. Use in pregnant women at term and in nursing mothers may cause kernicterus.
Increased risk of hypersensitivity reactions (SJS, TEN); hematologic toxicity (agranulocytosis, thrombocytopenia); hepatotoxicity; renal toxicity due to crystalluria; hemolytic anemia in G6PD-deficient patients; photosensitivity.
Monitor for hypersensitivity reactions, blood dyscrasias, and hepatic injury. Caution in elderly, folate deficiency, impaired renal/hepatic function, G6PD deficiency, and severe allergies or bronchial asthma. Avoid in infants <2 months of age. Use with caution in patients with porphyria or thyroid dysfunction.
Hypersensitivity to sulfonamides or trimethoprim; severe hepatic or renal impairment; megaloblastic anemia due to folate deficiency; pregnancy (especially first trimester and near term); lactation; pediatric patients <2 months of age.
Hypersensitivity to any component (sulfonamides, trimethoprim), severe liver damage, marked renal impairment (Cr Cl <15 ml/min), megaloblastic anemia due to folate deficiency, pregnancy at term, nursing mothers, infants <2 months of age.
No significant food interactions known. No dietary restrictions required.
Avoid high-potassium foods if at risk for hyperkalemia (e.g., bananas, oranges, salt substitutes). May reduce folic acid levels; encourage folate-rich foods (leafy greens, legumes). Take with food if GI upset occurs. Avoid alcohol due to disulfiram-like reaction.
Pregnancy category C. First trimester: Potential risk of neural tube defects based on animal studies. Second and third trimesters: Increased risk of premature closure of ductus arteriosus and oligohydramnios due to prostaglandin synthesis inhibition. Limited human data; avoid unless benefit outweighs risk.
First trimester: associated with increased risk of neural tube defects, cardiovascular malformations, and urinary tract anomalies due to folate antagonism (trimethoprim). Second and third trimesters: risk of kernicterus in the newborn due to sulfamethoxazole displacing bilirubin from albumin. Avoid during pregnancy, especially in the first and third trimesters.
Excreted in breast milk in low quantities. M/P ratio not established. Potential risk of adverse effects in nursing infants (e.g., renal dysfunction, bleeding). Use with caution if alternative therapies are not available.
Both components are excreted in breast milk. M/P ratio for sulfamethoxazole is approximately 0.3; for trimethoprim, approximately 1.1. Caution in infants with G6PD deficiency, hyperbilirubinemia, or jaundice. Consider alternatives, especially in preterm or sick infants.
No standard dosing adjustment during pregnancy. Increased renal clearance and volume of distribution in pregnancy may reduce efficacy; consider dose titration based on clinical response. Avoid in third trimester if possible.
Dose adjustments are not specifically recommended for pregnancy, but use with caution. Monitor serum drug levels if prolonged therapy. Avoid sulfamethoxazole near term due to risk of kernicterus. Ensure adequate folic acid supplementation (5 mg daily) to mitigate folate antagonism.
Cetamide (sulfacetamide sodium) is a topical ophthalmic sulfonamide used for bacterial conjunctivitis. Monitor for hypersensitivity, as cross-allergy with other sulfonamides may occur. Use with caution in patients with dry eye syndrome or corneal abrasions. Avoid prolonged use to prevent superinfection. Administer with clean hands and do not touch dropper tip to any surface.
Bactrim Pediatric (sulfamethoxazole/trimethoprim) is contraindicated in infants <2 months due to risk of kernicterus. Monitor for hyperkalemia, especially in elderly or renal impairment. Use with caution in folate deficiency; supplement folinic acid if prolonged therapy. Avoid in G6PD deficiency due to hemolytic anemia risk.
Wash hands before and after applying the eye drops.,Do not touch the dropper tip to your eye or any other surface.,Wait 5 minutes between different eye drops if using more than one type.,Complete the full course of treatment even if symptoms improve.,Do not wear contact lenses during treatment unless directed by your doctor.,Stop use and contact your doctor if you experience rash, itching, or swelling.,Keep the bottle tightly closed when not in use and store at room temperature.
Take with a full glass of water to prevent crystalluria.,Complete full course even if symptoms improve.,Avoid prolonged sun exposure; use sunscreen.,Report rash, fever, sore throat, or bruising immediately.,Do not use if allergic to sulfa drugs or thiazide diuretics.
"Sulfacetamide may reduce the efficacy of picosulfuric acid, a stimulant laxative, through antibiotic-mediated disruption of the gut microbiota. The conversion of picosulfate to its active metabolite, BHPM, relies on bacterial azoreductase enzymes in the colon. Sulfacetamide's antibacterial activity against colonic flora can decrease this bioactivation, leading to diminished laxative effect and potential treatment failure for constipation or bowel preparation."
"The risk or severity of adverse effects can be increased when Methenamine is combined with Sulfacetamide."
"The risk or severity of adverse effects can be increased when Sulfacetamide is combined with Mecamylamine."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about CETAMIDE vs BACTRIM PEDIATRIC, answered by our medical review team.
CETAMIDE is a Sulfonamide antibiotic that works by CETAMIDE is an antimicrobial combination of sulfadiazine (a sulfonamide) and trimethoprim. Sulfonamides inhibit dihydropteroate synthase, blocking folate synthesis; trimethoprim inhibits dihydrofolate reductase, producing sequential blockade of folic acid metabolism.. BACTRIM PEDIATRIC is a Sulfonamide Antibiotic Combination that works by Bactrim (sulfamethoxazole/trimethoprim) 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. Sequential blockade of folate synthesis leads to bacteriostasis.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between CETAMIDE and BACTRIM PEDIATRIC 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 CETAMIDE is: 500 mg orally every 6 hours; maximum 4 g per day.. The standard adult dose of BACTRIM PEDIATRIC is: Oral: 160 mg trimethoprim / 800 mg sulfamethoxazole (one DS tablet) every 12 hours for 14 days. For Pneumocystis jirovecii pneumonia: 15-20 mg/kg/day of trimethoprim component divided every 6-8 hours.. 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 CETAMIDE and BACTRIM PEDIATRIC 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. CETAMIDE is classified as Category C. Pregnancy category C. First trimester: Potential risk of neural tube defects based on animal studies. Second and third trimesters: Increased risk of premature closure of ductus art. BACTRIM PEDIATRIC is classified as Category C. First trimester: associated with increased risk of neural tube defects, cardiovascular malformations, and urinary tract anomalies due to folate antagonism (trimethoprim). Second an. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.