Generic
Sulphamethoxazole + Trimethoprim (Co-trimoxazole)
109 brands available in the market
At a glance
Co-trimoxazole (Sulphamethoxazole + Trimethoprim) is a combination antibiotic used for pneumonia, bronchitis, urinary tract, ear, and abdominal bacterial infections. It works by blocking two steps in bacterial folic acid production.
Description
Co-trimoxazole is a synergistic combination of Sulphamethoxazole and Trimethoprim. Sulphamethoxazole inhibits dihydrofolic acid formation from PABA; Trimethoprim inhibits conversion of dihydrofolic acid to tetrahydrofolic acid. This sequential blockade stops bacterial nucleic acid synthesis.
Indications
- Respiratory tract infections (bronchitis, bronchiectasis, pneumonia, sinusitis, otitis media)
- Urinary tract infections (cystitis, pyelonephritis, prostatitis, gonorrhea)
- Gastrointestinal infections (Salmonella, Shigella)
- Peritonitis
- Pneumocystis jiroveci pneumonia (PCP)
Therapeutic class
Anti-diarrheal Antimicrobial & Other Antibacterial Preparations
Pharmacological class
Sulfonamide + Dihydrofolate Reductase Inhibitor
Pharmacology
Co-trimoxazole provides sequential blockade of two steps in the bacterial folic acid synthesis pathway. Sulphamethoxazole inhibits dihydropteroate synthetase; Trimethoprim inhibits dihydrofolate reductase. This synergistic action stops bacterial protein and nucleic acid synthesis, producing bactericidal effects.
Mechanism of action
Stops bacterial growth by blocking two steps in folic acid synthesis.
Dosage
Adult Dose (Oral):
- Moderate infections: 2 tablets (480 mg) twice daily
- Severe infections: 2 tablets three times daily
- DS tablet: 1 tablet (960 mg) twice daily
- PCP: 120 mg/kg/day in 2-4 divided doses for 14-21 days
Pediatric Dose (Oral):
- 6-12 years: 2 teaspoonfuls syrup twice daily
- 6 months-5 years: 1 teaspoonful twice daily
- 6 weeks-6 months: 0.5 teaspoonful twice daily
Administration
- Take with food
- Shake syrup well before use
- Measure with a measuring cup
- Complete the full course as prescribed
Missed dose
If you miss a dose, take it as soon as you remember; if almost time for the next dose, skip it; do not double the dose.
Side effects
Common Side Effects:
- Nausea, vomiting
- Skin rash
- Allergic reactions
- Diarrhea
Serious (Rare):
- Crystalluria
- Hemolysis, thrombocytopenia
- Neutropenia, agranulocytosis
Precautions & warnings
- Do not use in hypersensitivity to sulfonamides or trimethoprim
- Do not use in severe liver failure, jaundice, severe renal impairment
- Do not use in porphyria, megaloblastic anemia
- Do not use in pregnancy and neonates (4 weeks)
Contraindications
- Hypersensitivity to trimethoprim or sulfonamides
- Severe hepatic failure
- Severe renal insufficiency (CrCl <15)
- Porphyria, megaloblastic anemia
- Neonates (4 weeks)
- Pregnancy (especially before birth)
Drug interactions
- Cyclosporine: Decreased blood concentrations
- Methotrexate: Increased toxicity
- Phenytoin: Inhibits clearance
- Warfarin, oral hypoglycemics: Potentiate action
- Pyrimethamine: Megaloblastic anemia (potentially fatal)
Food interactions
It is not known whether alcohol is safe with Co-trimoxazole; consult your doctor.
Use in pregnancy
Use in Pregnancy: Unsafe (Category D); evidence of risk to developing baby; use only in life-threatening situations; consult your doctor.
Pregnancy Category: D — always consult a doctor before taking during pregnancy.
Use in lactation
Use in Lactation: Safe during breastfeeding; human studies show insignificant passage into breast milk; however, skin rash in baby is possible; consult your doctor.
Pediatric use
Do not use in neonates (4 weeks); indicated for children
Geriatric use
Caution required in elderly patients
Renal / hepatic impairment
Renal Impairment: CrCl 15-30: half the standard dose; CrCl <15: do not use; consult your doctor.
Hepatic Impairment: Do not use in severe liver disease; consult your doctor.
Overdose effects
Overdose may cause nausea, vomiting, headache, confusion; provide symptomatic treatment; hemodialysis is effective.
Storage conditions
Store below 30°C, away from light and moisture; keep out of reach of children.
Chemical structure
Co-trimoxazole