Sulphamethoxazole + Trimethoprim

Generic Details

Generic Name

Sulphamethoxazole-trimethoprim

Other Names

  • Co-trimoxazole
  • TMP-SMX
  • Bactrim
  • Septra

Drug Class

  • Antibiotic
  • Combination of sulfonamide and dihydrofolate reductase inhibitor

Chemical Formula

C14H18N4O3S

Molecular Weight

310.4 g/mol

Mechanism of Action

  • Inhibition of bacterial folic acid synthesis by blocking two consecutive enzymatic steps

Indications

  • Urinary tract infections
  • Respiratory tract infections
  • Gastrointestinal infections
  • Skin and soft tissue infections
  • Pneumocystis pneumonia (PCP)
  • Toxoplasmosis
  • Traveler's diarrhea

Common Dosage Forms

  • Tablet
  • Suspension
  • Injection

Typical Dosage

  • Adults: 1 double-strength tablet (800 mg sulfamethoxazole/160 mg trimethoprim) every 12 hours
  • Pediatric: Dosage based on weight and age

Pediatric Dosage

  • Based on weight and age; consult healthcare provider

Geriatric Dosage

  • Adjust dosage based on kidney function

Side Effects

  • Nausea
  • Vomiting
  • Diarrhea
  • Allergic reactions
  • Rash
  • Photosensitivity
  • Hyperkalemia
  • Peripheral neuropathy

Contraindications

  • Hypersensitivity to sulfonamides or trimethoprim
  • Severe liver or kidney disease
  • Pregnancy (particularly at term)

Pregnancy Category

  • Category D - Potential risk of fetal harm if used during the last trimester

Lactation Safety

  • Caution advised; may excrete into breast milk

Drug Interactions

  • Warfarin (increased bleeding risk)
  • ACE inhibitors (hyperkalemia)
  • Methotrexate (increased methotrexate levels)

Overdose Symptoms

  • Nausea
  • Vomiting
  • Confusion
  • Convulsions
  • Bone marrow depression

Antidote for Overdose

  • Folinic acid (leucovorin) for dihydrofolate reductase inhibitor toxicity

Storage Conditions

  • Store at room temperature (15-30°C)
  • Protect from light and moisture

Pharmacokinetics

  • Absorption: Well-absorbed orally
  • Distribution: Widely distributed in body tissues and fluids
  • Metabolism: Hepatic metabolism
  • Excretion: Primarily excreted in the urine

Precautions

  • Monitor renal function
  • Stay hydrated while taking the medication

Warnings

  • Risk of severe skin reactions like Stevens-Johnson syndrome
  • Long-term use may lead to Clostridium difficile-associated diarrhea

Others