How Do Antibiotic Combos Work?

Antibiotic combos consist of a combination of two or more antibiotics used for treating:

• Chronic bronchitis
• Bacterial meningitis (inflammation of the brain and spinal cord membranes caused by bacterial infection)
• Sepsis (a life-threatening complication of an infection.)
• Shigellosis (an intestinal infection caused by a family of bacteria known as shigella)
• Traveler’s diarrhea
• Urinary tract infections

Sulfamethoxazole when given in combination with trimethoprim stops the bacteria from growing and multiplying and causes their death.

Sulfamethoxazole does not kill the bacteria but interferes with their ability to grow and multiply (bacteriostatic). Bacteria need folic acid for their growth and multiplication. A sulfa drug interrupts the bacteria’s ability to use folic acid, thus inhibiting the growth process. As a result, the bacteria fail to reproduce. As humans rely on diet for obtaining folic acid, they are usually safe against the adverse effects of inhibition of folate production.

Trimethoprim kills the bacteria by inhibiting the enzyme dihydrofolate reductase, thereby blocking the production of folic acid. Folic acid is essential for bacterial cells to survive, and the lack of this mineral can kill the bacteria.

Antibiotic combos are used for treating:

• Chronic bronchitis
• Bacterial meningitis
• Sepsis
• Shigellosis
• Traveler’s diarrhea
• Urinary tract infections
• Off-label use includes:
  • Acne vulgaris 
  • Community-acquired pneumonia

Antibiotic combos can cause the following side effects:

• Lethargy
• Diarrhea
• Anorexia
• Nausea
• Vomiting
• Dizziness
• Headache
• Photosensitivity 
• Serious skin rashes
• Stevens-Johnson syndrome, causing aching joints and muscles, redness, blistering and skin peeling
• Toxic epidermal necrolysis, causing difficulty in swallowing and peeling, redness, loosening, and blistering of the skin
• Hepatotoxicity (liver damage)
• Low white blood cell count
• Thrombocytopenia (low platelet count)
• Anemia

Generic and brand names of antibiotic combos include:

• Bactrim
• Bactrim DS
• Cotrim
• Cotrimoxazole
• Septra
• Septra DS
• Sulfatrim
• Trimethoprim/sulfamethoxazole