What effect does sulfamethoxazole have on trimethoprim?

Sulfamethoxazole has a synergistic effect when combined with trimethoprim. Both these medications are antibiotics, but they work in different ways to inhibit bacterial growth. Sulfamethoxazole is a sulfonamide that functions by interfering with the bacterial synthesis of folate, while trimethoprim inhibits a subsequent step in the same pathway.

When used together, they enhance each other's effects, leading to a more potent antibacterial action than either drug would achieve alone. This synergy allows for lower doses of each drug to be used, which can reduce the risk of side effects and resistance. The combination is commonly used to treat various infections, including urinary tract infections and some types of pneumonia, showcasing the clinical utility of their synergistic effect in improving treatment outcomes.