Dr. Greene`s Answer:
Septra and Bactrim are both brand names for a combination antibiotic called trimethoprim-sulfamethoxazole. This antibiotic is in widespread use. In children, the most common uses are for ear infections and urinary tract infections. It also has a role in the treatment of chronic bronchitis, traveler’s diarrhea, shigella, and in both the treatment and prevention of pneumocystis carinii pneumonia.
We all need folic acid (a B-complex vitamin) to survive. Most bacteria must manufacture their own supply of folic acid or folate. Animals (and some bacteria) depend on outside sources of folic acid, getting what they need from what they eat. Trimethoprim and sulfamethoxazole are both compounds that block the internal production of folic acid. Thus these compounds are relatively safe for humans, yet lethal to many bacteria. The combination product, Septra, is far more effective than either ingredient alone.
The sulfamethoxazole component of Septra is a sulfa (or sulfur containing) drug. It causes fewer side effects than the other sulfa drugs, but its side effects should be respected.
The most common significant adverse effects are allergic skin reactions. Most of these are mild, but occasionally they are quite severe. Septra should be discontinued at the first sign of a skin rash. Excess sun exposure should be avoided by anyone taking Septra.