Key takeaways
Metronidazole (Flagyl) and sulfamethoxazole/trimethoprim (Bactrim) are both antibiotics, but they belong to different classes and treat different types of infections. Metronidazole is a nitroimidazole antibiotic that targets bacterial and parasitic infections, such as bacterial vaginosis and trichomoniasis. In contrast, sulfamethoxazole/trimethoprim is a combination of a sulfonamide and an antifolate, used for infections like urinary tract infections (UTIs) and ear infections. Metronidazole is typically taken two to three times a day, while sulfamethoxazole/trimethoprim is usually taken twice a day. Both medications are available as lower-cost generics. However, metronidazole has a serious interaction with alcohol, requiring you to avoid it during treatment and for three days after. Sulfamethoxazole/trimethoprim can make your skin more sensitive to the sun and is not recommended if you have a sulfa allergy. Both medications have their own sets of side effects and specific warnings, so it's important to follow your healthcare provider's instructions closely.
